Abstract:
The amygdala has been implicated in a variety of functions, ranging from

Abstract:
A large number of studies have investigated the effects of chronic ethanol

Abstract:
Vitamin A and its derivatives, the retinoids, have recently been reported to be

Abstract:
Previous findings have suggested a critical role for hippocampal-lateral septal

Abstract:
Ample data indicate that cAMP-response element-binding protein (CREB) is essential for the formation of long-term memory in various species and learning systems. This implies that activated CREB could delineate neuronal circuits that subserve items in memory, while leaving open the possibility that the specifics of CREB activation itself contribute to the specificity of the internal representation encoded by the relevant circuit. We describe here the differential activation of CREB in the rat brain as a function of two related yet distinct forms of aversive conditioning: conditioned taste aversion (CTA) and conditioned context aversion (CCA). We found that CTA induces strong CREB activation in the insular cortex (IC) and the lateral septum (LS), but not in the parietal cortex (PC) and the medial septum (MS). In contrast, CCA results in strong activation in the PC and MS, but not in the IC and LS. These findings are congruent with a model that links differential pattern of activity within the LS and the MS with the acquisition of elemental versus contextual conditioning and, more generally, with the notion that CREB activation delineates learning-dependent circuits as a function of the type of cognitive process engaged.

Abstract:
The competitive antagonist 2-amino-5-phosphonoeptanoic acid (APV) was injected

Abstract:
To what extent the hippocampus is required for contextual conditioning remains a

Abstract:
A two-stage radial arm maze (RAM) task has been designed recently to demonstrate

Abstract:
The effects of ibotenate hippocampal lesions on discrimination performance in an

Abstract:
Although there is growing knowledge about intracellular mechanisms underlying

Abstract:
Subtype 3 of the ryanodine receptor (RYR3) is a ubiquitous Ca2+ release channel which is predominantly expressed in smooth muscle tissues and certain regions of the brain. We show by reverse transcription-polymerase chain reaction (RT-PCR) that non-pregnant mouse myometrial cells expressed only RYR3 and therefore could be a good model for studying the role of endogenous RYR3. Expression of RYR3 was confirmed by Western blotting and immunostaining. Confocal Ca2+ measurements revealed that in 1.7 mM extracellular Ca2+, neither caffeine nor photolysis of caged Ca2+ were able to trigger any Ca2+ responses, whereas in the same cells oxytocin activated propagated Ca2+ waves. However, under conditions of increased sarcoplasmic reticulum (SR) Ca2+ loading, brought about by superfusing myometrial cells in 10 mM extracellular Ca2+, all the myometrial cells responded to caffeine and photolysis of caged Ca2+, indicating that it was possible to activate RYR3. The caffeine-induced Ca2+ responses were inhibited by intracellular application of an anti-RYR3-specific antibody. Immunodetection of RYR3 with the same antibody revealed a rather homogeneous distribution of fluorescence in confocal cell sections. In agreement with these observations, spontaneous or triggered Ca2+ sparks were not detected. In conclusion, our results suggest that under conditions of increased SR Ca2+ loading, endogenous RYR3 may contribute to the Ca2+ responses of myometrial cells.

Abstract:
Heterodimeric class I phosphoinositide 3-kinase (PI3K) has been shown to be involved in the stimulation of voltage-gated Ca(2+) channels by various mediators. In this study, we bring evidences that vascular L-type Ca(2+) channels can be modulated by both tyrosine kinase-regulated class Ia and G protein-regulated class Ib PI3Ks. Purified recombinant PI3Ks increased the peak Ca(2+) channel current density when applied intracellularly. Furthermore, PI3Kalpha-, beta-, and delta-mediated stimulations of Ca(2+) channel currents were increased by preactivation by a phosphotyrosyl peptide, whereas PI3Kgamma- and beta-mediated effects were increased by Gbetagamma. In freshly isolated and cultured vascular myocytes, angiotensin II and Gbetagamma stimulated L-type Ca(2+) channel current. In contrast, platelet-derived growth factor (PDGF)-BB and the phosphotyrosyl peptide did not stimulate Ca(2+) channel current in freshly isolated cells despite the presence of endogenous PDGF receptors and PI3Kalpha and PI3Kgamma. Interestingly, when endogenous PI3Kbeta expression arose in cultured myocytes, both PDGF and phosphotyrosyl peptide stimulated Ca(2+) channels through PI3Kbeta, as revealed by the inhibitory effect of an anti-PI3Kbeta antibody. These results suggest that endogenous PI3Kbeta but not PI3Kalpha is specifically involved in PDGF receptor-induced stimulation of Ca(2+) channels and that different isoforms of PI3K regulate physiological increases of Ca(2+) influx in vascular myocytes stimulated by vasoconstrictor or growth factor.

Abstract:
Previous results have shown that in rat portal vein myocytes the betagamma dimer of the G(13) protein transduces the angiotensin II-induced stimulation of calcium channels and increase in intracellular Ca(2+) concentration through activation of phosphoinositide 3-kinase (PI3K). In the present work we determined which class I PI3K isoforms were involved in this regulation. Western blot analysis indicated that rat portal vein myocytes expressed only PI3Kalpha and PI3Kgamma and no other class I PI3K isoforms. In the intracellular presence of an anti-p110gamma antibody infused by the patch clamp pipette, both angiotensin II- and Gbetagamma-mediated stimulation of Ca(2+) channel current were inhibited, whereas intracellular application of an anti-p110alpha antibody had no effect. The anti-PI3Kgamma antibody also inhibited the angiotensin II- and Gbetagamma-induced production of phosphatidylinositol 3,4,5-trisphosphate. In Indo-1 loaded cells, the angiotensin II-induced increase in [Ca(2+)](i) was inhibited by intracellular application of the anti-PI3Kgamma antibody, whereas the anti-PI3Kalpha antibody had no effect. The specificity of the anti-PI3Kgamma antibody used in functional experiments was ascertained by showing that this antibody did not recognize recombinant PI3Kalpha in Western blot experiments. Moreover, anti-PI3Kgamma antibody inhibited the stimulatory effect of intracellularly infused recombinant PI3Kgamma on Ca(2+) channel current without altering the effect of recombinant PI3Kalpha. Our results show that, although both PI3Kgamma and PI3Kalpha are expressed in vascular myocytes, the angiotensin II-induced stimulation of vascular L-type calcium channel and increase of [Ca(2+)](i) involves only the PI3Kgamma isoform.

Abstract:
Vitamin A and its derivatives, the retinoids, have been implicated recently in

Abstract:
Using an antisense strategy, we have previously shown that in vascular myocytes, subtypes 1 and 2 of ryanodine receptors (RYRs) are required for Ca(2+) release during Ca(2+) sparks and global Ca(2+) responses, evoked by activation of voltage-gated Ca(2+) channels, whereas RYR subtype 3 (RYR3) has no contribution. Here, we investigated the effects of increased Ca(2+) loading of the sarcoplasmic reticulum (SR) on the RYR-mediated Ca(2+) responses and the role of the RYR3 by injecting antisense oligonucleotides targeting the RYR subtypes. RYR3 expression was demonstrated by immunodetection in both freshly dissociated and cultured rat portal vein myocytes. Confocal Ca(2+) measurements revealed that the number of cells showing spontaneous Ca(2+) sparks was strongly increased by superfusing the vascular myocytes in 10 mm Ca(2+)-containing solution. These Ca(2+) sparks were blocked after inhibition of RYR1 or RYR2 by treatment with antisense oligolucleotides but not after inhibition of RYR3. In contrast, inhibition of RYR3 reduced the global Ca(2+) responses induced by caffeine and phenylephrine, indicating that RYR3 participated together with RYR1 and RYR2 to these Ca(2+) responses in Ca(2+)-overloaded myocytes. Ca(2+) transients evoked by photolysis of caged Ca(2+) with increasing flash intensities were also reduced after inhibition of RYR3 and revealed that the [Ca(2+)](i) sensitivity of RYR3 would be similar to that of RYR1 and RYR2. Our results show that, under conditions of increased SR Ca(2+) loading, the RYR3 becomes activable by caffeine and local increases in [Ca(2+)](i).

Abstract:
1. Previous data have shown that activation of beta(3)-adrenoceptors stimulates vascular L-type Ca(2+) channels through a G alphas-induced stimulation of the cyclic AMP/PKA pathway. The present study investigated whether beta-adrenergic stimulation also uses the G beta gamma/PI3K/PKC pathway to modulate L-type Ca(2+) channels in rat portal vein myocytes. 2. Peak Ba(2+) current (I(Ba)) measured using the whole-cell patch clamp method was maximally increased by application of 10 microm isoprenaline after blockade of beta(3)-adrenoceptors by 1 microM SR59230A. Under these conditions, the isoprenaline-induced stimulation of I(Ba) was reversed by ICI-118551 (a specific beta(2)-adrenoceptor antagonist) but not by atenolol (a specific beta(1)-adrenoceptor antagonist). The beta(2)-adrenoceptor agonist salbutamol increased I(Ba), an effect which was reversed by ICI-118551 whereas the beta(1)-adrenoceptor agonist dobutamine had no effect on I(Ba). 3. Application of PKA inhibitors (H-89 and Rp 8-Br-cyclic AMPs) or a PKC inhibitor (calphostin C) alone did not affect the beta(2)-adrenergic stimulation of I(Ba) whereas simultaneous application of both PKA and PKC inhibitors completely blocked this stimulation. 4. The beta(2)-adrenergic stimulation of L-type Ca(2+) channels was blocked by a pre-treatment with cholera toxin and by intracellular application of an anti-G alphas antibody (directed against the carboxyl terminus of G alphas). In the presence of H-89, intracellular infusion of an anti-Gss(com) antibody or a beta ARK(1) peptide as well as a pre-treatment with wortmannin (a PI3K inhibitor) blocked the beta(2)-adrenergic stimulation of I(Ba). 5. These results suggest that the beta(2)-adrenergic stimulation of vascular L-type Ca(2+) channels involves both G alphas and G beta gamma subunits which exert their stimulatory effects through PKA and PI3K/PKC pathways, respectively.

Abstract:
Localized Ca(2+)-release signals (puffs) and propagated Ca(2+) waves were characterized in rat ureteric myocytes by confocal microscopy. Ca(2+) puffs were evoked by photorelease of low concentrations of Ins(1,4,5)P(3) from a caged precursor and by low concentrations of acetylcholine; they were also observed spontaneously in Ca(2+)-overloaded myocytes. Ca(2+) puffs showed some variability in amplitude, time course and spatial spread, suggesting that Ins(1,4,5)P(3)-gated channels exist in clusters containing variable numbers of channels and that within these clusters a variable number of channels can be recruited. Immunodetection of Ins(1,4,5)P(3) receptors revealed the existence of several spots of fluorescence in the confocal cell sections, supporting the existence of clusters of Ins(1,4,5)P(3) receptors. Strong Ins(1,4,5)P(3) photorelease and high concentrations of acetylcholine induced Ca(2+) waves that originated from an initiation site and propagated in the whole cell by spatial recruitment of neighbouring Ca(2+)-release sites. Both Ca(2+) puffs and Ca(2+) waves were blocked selectively by intracellular applications of heparin and an anti-Ins(1,4,5)P(3)-receptor antibody, but were unaffected by ryanodine and intracellular application of an anti-ryanodine receptor antibody. mRNAs encoding for the three subtypes of Ins(1,4,5)P(3) receptor and subtype 3 of ryanodine receptor were detected in these myocytes, and the maximal binding capacity of [(3)H]Ins(1,4,5)P(3) was 10- to 12-fold higher than that of [(3)H]ryanodine. These results suggest that Ins(1,4,5)P(3)-gated channels mediate a continuum of Ca(2+) signalling in smooth-muscle cells expressing a high level of Ins(1,4,5)P(3) receptors and no subtypes 1 and 2 of ryanodine receptors.

Abstract:
The present work was aimed at determining, both at the psychological and at the neurobiological levels, aspects of rodent memory that fall into line with human declarative memory which is known to be selectively impaired in amnesic subjects and during the course of ageing. The ability to compare and to contrast items in memory, and to support inferential use of memories in novel situations (flexibility), were considered to be the two key psychological features of human declarative memory that were altered by both hippocampal lesions and hippocampal dysfunction. Adult and aged mice were trained on learning tasks using two-stage paradigms, the aim of which was to assess memory performance through these two psychological aspects in the same subjects. Results suggest that ageing specifically impairs the ability to both compare and contrast items in memory (declarative/relational memory based on complex associations), without altering memory based on simple S-R associations (procedural memory). Hippocampal lesions in adult mice produced the same dissociation between relational memory (impaired) and procedural memory (spared). Pharmacological experiments showed that, depending on the drug used, the relational memory deficit of aged mice may be selectively reversed (i.e. without changes in procedural memory) and that the behavioural efficacy of certain treatments was shown to parallel their potency in re-establishing normal (i.e. adult) levels of hippocampal plasticity-related mechanisms. Together with previous findings, these results suggest that the storage and use of relational representations would critically depend on the plasticity of hippocampal synapses, which via their connections with cortical areas, would support the storage of associations between perceptual, behavioral and cognitive events.

Abstract:
In this study, Gbeta specificity in the regulation of Gbetagamma-sensitive phosphoinositide 3-kinases (PI3Ks) and phospholipase Cbeta (PLCbeta) isozymes was examined. Recombinant mammalian Gbeta(1-3)gamma(2) complexes purified from Sf9 membranes stimulated PI3Kgamma lipid kinase activity with similar potency (10-30 nm) and efficacy, whereas transducin Gbetagamma was less potent. Functionally active Gbeta(5)gamma(2) dimers were purified from Sf9 cell membranes following coexpression of Gbeta(5) and Ggamma(2-His). This preparation as well as Gbeta(1)gamma(2-His) supported pertussis toxin-mediated ADP-ribosylation of Galpha(i1). Gbeta(1)gamma(2-His) stimulated PI3Kgamma lipid and protein kinase activities at nanomolar concentrations, whereas Gbeta(5)gamma(2-His) had no effect. Accordingly, Gbeta(1)gamma(2-His), but not Gbeta(5)gamma(2-His), significantly stimulated the lipid kinase activity of PI3Kbeta in the presence or absence of tyrosine-phosphorylated peptides derived from the p85-binding domain of the platelet derived-growth factor receptor. Conversely, both preparations were able to stimulate PLCbeta(2) and PLCbeta(1). However, Gbeta(1)gamma(2-His), but not Gbeta(5)gamma(2-His), activated PLCbeta(3). Experimental evidence suggests that the mechanism of Gbeta(5)-dependent effector selectivity may differ between PI3K and PLCbeta. In conclusion, these data indicate that Gbeta subunits are able to discriminate among effectors independently of Galpha due to selective protein-protein interaction.

Abstract:
It has been demonstrated previously on the radial maze that the emergence of an

Abstract:
1. The effects of beta(3)-adrenergic stimulation were studied on the L-type Ca(2+) channel in single myocytes from rat portal vein using the whole-cell mode of the patch-clamp technique. 2. Reverse transcription-polymerase chain reaction showed that beta(1)-, beta(2)- and beta(3)-adrenoceptor subtypes were expressed in rat portal vein myocytes. Application of both propranolol (a non-selective beta(1)- and beta(2)-adrenoceptor antagonist) and SR59230A (a beta(3)-adrenoceptor antagonist) were needed to inhibit the isoprenaline-induced increase in L-type Ca(2+) channel current. 3. L-type Ca(2+) channels were stimulated by CGP12177A (a beta(3)-adrenoceptor agonist with potent beta(1)- and beta(2)-adrenoceptor antagonist property) in a manner similar to that of isoprenaline. The CGP12177A-induced stimulation of Ca(2+) channel current was blocked by SR59230A, cyclic AMP-dependent protein kinase inhibitors, H-89 and Rp 8-Br-cyclic AMPs, but was unaffected by protein kinase C inhibitors, GF109203X and 19-31 peptide. This stimulation was mimicked by forskolin and 8-Br-cyclic AMP. In the presence of okadaic acid (a phosphatase inhibitor), the beta(3)-adrenoceptor-induced stimulation was maintained after withdrawal of the agonist. 4. The beta(3)-adrenoceptor stimulation of L-type Ca(2+) channels was blocked by a pretreatment with cholera toxin and by the intracellular application of an anti-Galpha(s) antibody. This stimulation was unaffected by intracellular infusion of an anti-Gbeta(com) antibody and a betaARK(1) peptide. 5. These results show that activation of beta(3)-adrenoceptors stimulates L-type Ca(2+) channels in vascular myocytes through a Galpha(s)-induced stimulation of the cyclic AMP/protein kinase A pathway and the subsequent phosphorylation of the channels.

Abstract:
While the roles of subtypes 1 and 2 of the ryanodine receptors (RYRs) have been studied in cellular systems expressing specifically one or the other of these subtypes (i.e. skeletal and cardiac muscle), the function of these receptors has not been evaluated in smooth muscles. We have previously reported RYR-mediated elementary (Ca(2+) sparks) and global Ca(2+) responses in rat portal vein myocytes. Here, we investigated the respective roles of all three RYR subtypes expressed in these cells as revealed by reverse transcriptase-polymerase chain reaction. Antisense oligonucleotides targeting each one of the three RYR subtypes were shown to specifically inhibit the expression of the corresponding mRNA and protein without affecting the other RYR subtypes. Confocal Ca(2+) measurements revealed that depolarization-induced Ca(2+) sparks and global Ca(2+) responses were blocked when either RYR1 or RYR2 expression was suppressed. Caffeine-induced Ca(2+) responses were partly inhibited by the same antisense oligonucleotides. Neither the corresponding scrambled oligonucleotides nor the antisense oligonucleotides targeting RYR3 affected depolarization- or caffeine-induced Ca(2+) responses. Our results show that, in vascular myocytes, the two RYR1 and RYR2 subtypes are required for Ca(2+) release during Ca(2+) sparks and global Ca(2+) responses, evoked by activation of voltage-gated Ca(2+) channels.

Abstract:
Previous experiments using a classical fear conditioning paradigm have provided

Abstract:
The present study was built on the original report of Eichenbaum et al.

Abstract:
In rat portal vein myocytes, Ca(2+) signals can be generated by inositol 1,4,5-trisphosphate (InsP(3))- and ryanodine-sensitive Ca(2+) release channels, which are located on the same intracellular store. Using a laser scanning confocal microscope associated with the patch-clamp technique, we showed that propagated Ca(2+) waves evoked by norepinephrine (in the continuous presence of oxodipine) were completely blocked after internal application of an anti-InsP(3) receptor antibody. These propagated Ca(2+) waves were also reduced by approximately 50% and transformed in homogenous Ca(2+) responses after application of an anti-ryanodine receptor antibody or ryanodine. All-or-none Ca(2+) waves obtained with increasing concentrations of norepinephrine were transformed in a dose-response relationship with a Hill coefficient close to unity after ryanodine receptor inhibition. Similar effects of the ryanodine receptor inhibition were observed on the norepinephrine- and ACh-induced Ca(2+) responses in non-voltage-clamped portal vein and duodenal myocytes and on the norepinephrine-induced contraction. Taken together, these results show that ryanodine-sensitive Ca(2+) release channels are responsible for the fast propagation of Ca(2+) responses evoked by various neurotransmitters producing InsP(3) in vascular and visceral myocytes.

Abstract:
In this study, we identified the receptor subtype activated by endothelin-1 (ET-1) and the subunit composition of the G protein coupling this receptor to increase in cytosolic Ca2+ concentration in rat portal vein myocytes. We used intranuclear antisense oligonucleotide injection to selectively inhibit the expression of G protein subunits. We show here that the endothelin receptor subtype A (ETA)-mediated increase in cytosolic Ca2+ concentration was mainly dependent on Ca2+ release from the intracellular store. ETA receptor-mediated Ca2+ release was selectively inhibited by antisense oligonucleotides that inhibited the expression of alpha11, beta3, and gamma5 subunits, as checked by immunocytochemistry. Intracellular dialysis of a carboxyl terminal anti-betacom antibody and a peptide corresponding to the Gbetagamma binding region of the beta-adrenergic receptor kinase-1 had no effect on the ETA receptor-mediated Ca2+ release. In contrast, a synthetic peptide corresponding to the carboxyl terminus of the alphaq/alpha11 subunit, heparin (an inhibitor of inositol 1,4,5-trisphosphate receptors), and U73122 (an inhibitor of phosphatidylinositol-phospholipase C) inhibited, in a concentration-dependent manner, the ETA receptor-mediated Ca2+ responses. Accumulation of [3H]inositol trisphosphate evoked by norepinephrine peaked at approximately 15 s, whereas that evoked by ET-1 progressively increased within 2 min. In myocytes injected with anti-alphaq antisense oligonucleotides, both amplitude and time course of the norepinephrine-induced Ca2+ release became similar to those of the ET-1-induced Ca2+ response. We conclude that the ETA receptor-mediated Ca2+ release is selectively transduced by the heterotrimeric G11 protein composed of alpha11, beta3, and gamma5 subunits, and that a delayed stimulation of phospholipase C occurs via the alpha11 subunit.

Abstract:
We have previously reported that, in venous myocytes, Gbetagamma scavengers inhibit angiotensin AT1A receptor-induced stimulation of L-type Ca2+ channels (1). Here, we demonstrate that intracellular infusion of purified Gbetagamma complexes stimulates the L-type Ca2+ channel current in a concentration-dependent manner. Additional intracellular dialysis of GDP-bound inactive Galphao or of a peptide corresponding to the Gbetagamma binding region of the beta-adrenergic receptor kinase completely inhibited the Gbetagamma-induced stimulation of Ca2+ channel currents. The gating properties of the channel were not affected by intracellular application of Gbetagamma, suggesting that Gbetagamma increased the whole-cell calcium conductance. In addition, both the angiotensin AT1A receptor- and the Gbetagamma-induced stimulation of L-type Ca2+ channels were blocked by pretreatment of the cells with wortmannin, at nanomolar concentrations. Correspondingly, intracellular infusion of an enzymatically active purified recombinant Gbetagamma-sensitive phosphoinositide 3-kinase, PI3Kgamma, mimicked Gbetagamma-induced stimulation of Ca2+ channels. Both Gbetagamma- and PI3Kgamma-induced stimulations of Ca2+ channel currents were reduced by protein kinase C inhibitors suggesting that the Gbetagamma/PI3Kgamma-activated transduction pathway involves a protein kinase C. These results indicate for the first time that Gbetagamma dimers stimulate the vascular L-type Ca2+ channels through a Gbetagamma-sensitive PI3K.

Abstract:
Ca2+ signalling events were analyzed in single myocytes from rat portal vein by using a laser confocal microscope combined with the patch-clamp technique. Increase in inositol 1,4,5-trisphosphate (InsP3) concentration was obtained by photorelease from a caged precursor or intracellular dialysis of 3F-InsP3. Low InsP3 concentrations activated either small elevations of [Ca2+]i or localized Ca2+ transients whereas high InsP3 concentrations activated either homogeneous Ca2+ responses or propagated Ca2+ waves. The InsP3-evoked localized Ca2+ transients had spatio-temporal properties characteristic of Ca2+ sparks. In addition, compounds that blocked Ca2+ sparks and Ca2+ responses activated by Ca2+ jumps reduced the global InsP3-activated Ca2+ responses and suppressed the Ca2+ transients. In contrast, Ca2+ responses evoked by flash-photolytic Ca2+ jumps or caffeine were not affected by heparin (an InsP3 receptor antagonist). These results suggest that the absence of elementary Ca2+ events evoked by InsP3 may be related to the lack of clustered InsP3 receptor units in these cells, as confirmed by immunocytochemistry. Cooperativity between InsP3- and ryanodine-sensitive Ca2+ channels may represent a novel mechanism to amplify Ca2+ release from the same intracellular store and give rise to propagated Ca2+ waves.

Abstract:
The molecular diversity of receptors and the capability of these receptors to activate multiple types of G proteins theoretically allow the transmission of signals through multiple effector pathways. In functional experiments, however, the number of possibilities may be strongly reduced. We have recently reported that in vascular myocytes, alpha(1)-adrenoceptors activate two G proteins composed of alpha(q)/beta(1)/gamma(3) and alpha(11)/beta(3)/gamma(2) subunits, leading to increase in cytoplasmic [Ca(2+)](i) concentration. Only the alpha(q) subunit transduces the signal to a phospholipase C-beta, which hydrolyzes phosphatidylinositol 4,5-bisphosphate to generate inositol 1,4,5-trisphosphate and the subsequent release of Ca(2+) from the intracellular store. In contrast, the alpha(11) subunit activates Ca(2+) entry through a nonspecific cation channel in the presence of increased [Ca(2+)](i) level. These coupling mechanisms reveal the distinct participation of G(q) and G(11) in the regulation of vascular contractility. Specific G(q)- or G(11)-activated pathways should be taken into account to understand the various contraction profiles induced by different vasoconstrictors.

Abstract:
Rats with lesions either of medial septal nucleus (MSN) or the entorhinal cortex

Abstract:
Adult and aged mice were submitted to a discrimination task in a radial maze

Abstract:
Recent data obtained using a classic fear conditioning paradigm showed a

Abstract:
Ca2+ signalling events and whole-cell Ca2+ currents were analyzed in single myocytes from rat portal vein by using a laser scanning confocal microscope combined with the patch-clamp technique. In myocytes in which the intracellular Ca2+ store was depleted or Ca2+ release channels were blocked by 10 microM ryanodine, inward Ca2+ currents induced slow and sustained elevations of [Ca2+]i. These Ca2+ responses were suppressed by 1 microM oxodipine and by depolarizations to +120 mV, a potential close to the reversal potential for Ca2+ ions, suggesting that they reflected Ca2+ influx through L-type Ca2+ channels. With functioning intracellular Ca2+ stores, flash photolysis of caged Ca2+ gave rise to a small increase in [Ca2+]i with superimposed Ca2+ sparks, reflecting the opening of clustered Ca2+ release channels. Brief Ca2+ currents in the voltage range from -30 to +10 mV triggered Ca2+ sparks or macrosparks that did not propagate in the entire line-scan image. Increasing the duration of Ca2+ current for 100 ms or more allowed the trigger of propagating Ca2+ waves which originated from the same initiation sites as the caffeine-activated response. Both Ca2+ sparks and initiation sites of Ca2+ waves activated by Ca2+ currents were observed in the vicinity of areas that excluded the Ca2+ probes, reflecting infoldings of the plasma membrane close to the sarcoplasmic reticulum, as revealed by fluorescent markers. The hierarchy of Ca2+ signalling events, from submicroscopic fundamental events to elementary events (sparks) and propagated waves, provides an integrated mechanism to regulate vascular tone.

Abstract:
A G protein composed of alpha13, beta1, and gamma3 subunits selectively couples the angiotensin AT1A receptors to increase cytoplasmic Ca2+ concentration ([Ca2+]i) in rat portal vein myocytes (Macrez-Lepretre, N., Kalkbrenner, F., Morel, J. L., Schultz, G., and Mironneau, J. (1997) J. Biol. Chem. 272, 10095-10102). We show here that Gbetagamma transduces the signal leading to stimulation of L-type Ca2+ channels. Intracellular dialysis through the patch pipette of a carboxyl-terminal anti-betacom antibody and a peptide corresponding to the Gbetagamma binding region of the beta-adrenergic receptor kinase 1 inhibited the stimulation of Ca2+ channels and the increase in [Ca2+]i evoked by angiotensin II. The Gbetagamma binding peptide did not prevent the dissociation of the heterotrimeric G protein into its subunits, as it did not block activation of phospholipase C-beta by Galphaq in response to stimulation of alpha1-adrenoreceptors. Transient overexpression of the beta-adrenergic receptor kinase 1 fragment and of Galpha subunits also inhibited the angiotensin II-induced increase in [Ca2+]i. Both anti-alpha13 antibody and carboxyl-terminal alpha13 peptide abrogated the angiotensin II-induced stimulation of Ca2+ channels. We conclude that activation of angiotensin AT1 receptors requires all three alpha, beta, and gamma subunits of G13 for receptor-G protein interaction, whereas the transduction of the signal to L-type Ca2+ channels is mediated by Gbetagamma.

Abstract:
1. Cytosolic Ca2+ concentration ([Ca2+]i) during exposure to acetylcholine or caffeine was measured in mouse duodenal myocytes loaded with fura-2. Acetylcholine evoked a transient increase in [Ca2+]i followed by a sustained rise which was rapidly terminated after drug removal. Although L-type Ca2+ currents participated in the global Ca2+ response induced by acetylcholine, the initial peak in [Ca2+]i was mainly due to release of Ca2+ from intracellular stores. 2. Atropine, 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, a muscarinic M3 antagonist), pirenzepine (a muscarinic M1 antagonist), methoctramine and gallamine (muscarinic M2 antagonists) inhibited the acetylcholine-induced Ca2+ release, with a high affinity for 4-DAMP and atropine and a low affinity for the other antagonists. Selective protection of muscarinic M2 receptors with methoctramine during 4-DAMP mustard alkylation of muscarinic M3 receptors provided no evidence for muscarinic M2 receptor-activated [Ca2+]i increase. 3. Acetylcholine-induced Ca2+ release was blocked by intracellular dialysis with a patch pipette containing either heparin or an anti-phosphatidylinositol antibody and by external application of U73122 (a phospholipase C inhibitor). 4. Acetylcholine-induced Ca2+ release was insensitive to external pretreatment with pertussis toxin, but concentration-dependently inhibited by intracellular dialysis with a patch pipette solution containing an anti-alpha q/alpha 11 antibody. An antisense oligonucleotide approach revealed that only the Gq protein was involved in acetylcholine-induced Ca2+ release. 5. Intracellular applications of either an anti-beta com antibody or a peptide corresponding to the G beta gamma binding domain of the beta-adrenoceptor kinase 1 had no effect on acetylcholine-induced Ca2+ release. 6. Our results show that, in mouse duodenal myocytes, acetylcholine-induced release of Ca2+ from intracellular stores is mediated through activation of muscarinic M3 receptors which couple with a Gq protein to activate a phosphatidylinositol-specific phospholipase C.

Abstract:
The subunit composition of angiotensin AT1 receptor-activated G protein was identified by using antisense oligonucleotide injection into the nucleus of rat portal vein myocytes. In these cells, we have previously shown that increases in the cytoplasmic calcium concentration ([Ca2+]i) induced by activation of angiotensin AT1 receptors were dependent on extracellular Ca2+ entry by L-type Ca2+ channels and subsequent Ca2+-induced Ca2+ release from the intracellular stores. The angiotensin AT1 receptor-activated increases in [Ca2+]i were selectively inhibited by injection of antisense oligonucleotides directed against the mRNAs coding for the alpha13, beta1, and gamma3 subunits. A correlating reduction in Galpha13, Gbeta1, and Ggamma3 protein expression was confirmed by immunocytochemistry. In addition, anti-alpha13 antibody and synthetic peptide corresponding to the carboxyl terminus of the Galpha13 subunit inhibited, in a concentration-dependent manner, the angiotensin AT1 receptor-mediated Ca2+ response. Reverse transcription-polymerase chain reaction analysis showed that only the angiotensin AT1A receptor was expressed in rat portal vein smooth muscle. Furthermore, injection of anti-AT1A oligonucleotides selectively inhibited the angiotensin II-induced increase in [Ca2+]i. We conclude that the receptor-activated signal leading to increases in [Ca2+]i is transduced by the heterotrimeric G13 protein composed of alpha13/beta1/gamma3 subunits and that the carboxyl terminus of the Galpha13 subunit interacts with the angiotensin AT1A receptor.

Abstract:
In this study, we identified the subunit composition of Gq and G11 proteins coupling alpha1-adrenoreceptors to increase in cytoplasmic Ca2+ concentration ([Ca2+]i) in rat portal vein myocytes maintained in short-term primary culture. We used intranuclear antisense oligonucleotide injection to inhibit selectively the expression of subunits of G protein. Increases in [Ca2+]i were measured in response to activation of alpha1-adrenoreceptors, angiotensin AT1 receptors, and caffeine. Antisense oligonucleotides directed against the mRNAs coding for alphaq, alpha11, beta1, beta3, gamma2, and gamma3 subunits selectively inhibited the increase in [Ca2+]i activated by alpha1-adrenoreceptors. A corresponding reduction of the expression of these G protein subunits was immunochemically confirmed. In experiments performed in Ca2+-free solution only cells injected with anti-alphaq antisense oligonucleotides displayed a reduction of the alpha1-adrenoreceptor-induced Ca2+ release. In contrast, in Ca2+-containing solution, injection of anti-alpha11 antisense oligonucleotides suppressed the alpha1-adrenoreceptor-induced stimulation of the store-operated Ca2+ influx. Agents that specifically bound Gbetagamma subunits (anti-betacom antibody and overexpression of a beta-adrenergic receptor kinase carboxyl-terminal fragment) had no effect on the alpha1-adrenoreceptor-induced signal transduction. Taken together, these results suggest that alpha1-adrenoreceptors utilize two different Galpha subunits to increase [Ca2+]i. Galphaq may activate phosphatidylinositol 4,5-bisphosphate hydrolysis and induce release of Ca2+ from intracellular stores. Galpha11 may enhance the Ca2+-activated Ca2+ influx that replenishes intracellular Ca2+ stores.

Abstract:
The action of angiotensin II (ANG II) was studied in single myocytes from rat portal vein, in which the cytoplasmic Ca++ concentration was estimated by emission from fluorescent dyes and the Ca++ channel current was measured with the whole-cell mode of the patch-clamp technique. ANG II stimulated Ca++ channel current through L-type Ca++ channels and initiated a slow and small increase in the cytoplasmic Ca++ concentration in cells in which intracellular Ca++ stores had been depleted by pretreatment with ryanodine and caffeine. Both Ca++ channel current stimulation and Ca++ responses were selectively inhibited by losartan, indicating activation of angiotensin AT1 receptors. Activation of Ca++ channels by ANG II was insensitive to treatment with pertussis toxin and cholera toxin. Intracellular applications of anti-G alpha q/alpha 11 and anti-phosphatidylinositol antibodies had no effect on the ANG II-induced stimulation of Ca++ channel current, indicating that phosphatidylinositol-specific phospholipase C was not involved in this signaling pathway. Down-regulation of protein kinase C and application of an inhibitor of protein kinase C blocked the ANG II-induced effects. Tricyclodecan-9-yl xanthogenate (an inhibitor of non-phosphatidylinositol-specific phospholipases C and phospholipases D) but not propranolol (an inhibitor of phospholipase D-derived diacylglycerol formation) suppressed the ANG II-induced effects. These data suggest that phosphatidylcholine-specific phospholipase C is involved in the ANG II signaling pathway leading to stimulation of L-type Ca++ channels by protein kinase C.

Abstract:
Ca2+ release from intracellular stores was examined with the use of a confocal microscope in single, voltage-clamped myocytes from rat portal vein loaded with both Fluo-3 and Fura-red. Spontaneous local increases in [Ca2+]i from the sarcoplasmic reticulum, termed Ca2+ sparks, were observed in about 30% of the quiescent cells tested. Ca2+ sparks could be evoked by low concentrations of caffeine (1 mM) or ryanodine (1 microM). Both spontaneous and caffeine-evoked Ca2+ sparks were insensitive to blockers of voltage-dependent Ca2+ channels. Caffeine (10 mM) triggered propagating Ca2+ waves of large amplitude which started from the same site than spontaneous Ca2+ sparks in 73% of the cells, as expected if Ca2+ sparks were the elementary events that could account for the initiation of Ca2+ waves. Spontaneous Ca2+ sparks activated both Ca(2+)-dependent K+ and non-selective cation currents, whereas Ca2+ waves were able to evoke Ca(2+)-dependent chloride current. These results suggest that both inward cation current and outward K+ current activated by Ca2+ sparks may exert a key role in controlling the basal activity of vascular myocytes.

Abstract:
Contraction in smooth muscle is triggered by an increase in cytoplasmic free calcium ([Ca2+]i) which depends on both Ca2+ influx through L-type Ca2+ channels and Ca2+ release from the sarcoplasmic reticulum (SR). Two mechanisms have been shown to be involved in SR Ca2+ release, one is stimulated by Ca2+ and involved ryanodine-sensitive Ca2+-release channels; the other is stimulated by an increase in inositol 1,4,5-trisphosphate (InsP3) generation induced by various mediators and involved InsP3-sensitive Ca2+ release channels. Here, we examined the effects of angiotensin II on [Ca2+]i in single rat portal vein myocytes using both the whole cell patch-clamp method and a laser scanning confocal microscope. Elementary Ca2+ release events (Ca2+ sparks) were obtained spontaneously or in response to L-type Ca2+ channel current activation, and resulted from activation of ryanodine-sensitive Ca2+-release channels in the SR. We show that angiotensin AT1 receptors stimulate Ca2+ sparks through activation of L-type Ca2+ channels without involving InsP3-induced Ca2+ release. This novel transduction pathway may be a common mechanism for vasoconstrictors which do not stimulate generation of chemical second messengers.

Abstract:
The ability of phospholipase C inhibitors to inhibit Ca2+ channel stimulation and Ca2+ release from intracellular stores evoked by norepinephrine in single rat portal vein myocytes was investigated in the aim of identifying the type of phospholipase C involved in the transduction pathways activated by alpha 1A- and alpha 2A-adrenoceptors. U73122 (an inhibitor of phosphatidylinositol-phospholipase C) inhibited in a concentration-dependent manner the release of Ca2+ from the intracellular stores induced by activation of alpha 1A-adrenoceptors and related to inositol phosphate production whereas U73343 was ineffective. Both compounds had no effect on the release of Ca2+ induced by caffeine. However, U73122 and U73343 inhibited the L-type Ca2+ channel. D609 (an inhibitor of phosphatidylcholine-phospholipase C) had no direct inhibitory effects on the L-type Ca2+ channel but it inhibited concentration dependently the alpha 2A-adrenoceptor-induced stimulation of Ca2+ channels, which had been shown to be independent of phosphatidylinositol hydrolysis. Therefore, these results suggest that alpha 2A-adrenoceptors activate a phosphatidylcholine-phospholipase C in vascular myocytes. However, D609 had other sites of action as it blocked norepinephrine- and caffeine-induced Ca2+ release from the intracellular stores.

Abstract:
In the pregnant rat myometrium, an averaged 30% of inositol phosphate accumulation induced by carbachol and oxytocin was inhibited by oxodipine indicating that a part of receptor-mediated generation of inositol phosphates depended on Ca++ influx through voltage-gated Ca++ channels. In fura-2-loaded cells, carbachol and oxytocin caused a two-phase [Ca++]i response, made up of a transient [Ca++]i peak of about 700 nM followed by a sustained phase of about 120 nM. Oxodipine reduced the [Ca++]i peak by 40% and the plateau phase by 50%, pointing to a contribution of Ca++ influx in both the [Ca++]i peak and sustained phase. Isoproterenol reduced inositol phosphate response to carbachol and oxytocin to an amount equivalent to that elicited by oxodipine. No additional reduction could be obtained in a combination of isoproterenol and oxodipine. Isoproterenol decreased by 40% the [Ca++]i peak and by 70% the [Ca++]i plateau phase. Differently from isoproterenol, forskolin did not affect inositol phosphate accumulation induced by oxytocin and failed to attenuate the [Ca++]i peak. The inhibitory effect of isoproterenol on both inositol phosphate accumulation and [Ca++]i increase induced by oxytocin was abolished by pertussis toxin. These data suggest that beta adrenergic receptor activation is linked via a cAMP-independent, pertussis toxin-sensitive process to an activation of K+ channels, as revealed by use of selective K+ channel antagonists, with the consequent closure of voltage-gated Ca++ channels, resulting in the inhibition of the Ca(++)-associated generation of inositol phosphates.

Abstract:
We report two experiments conducted on a radial arm maze in the mouse showing

Abstract:
In rat portal vein myocytes, alpha 2A-adrenoceptors activate voltage-dependent Ca2+ channels via a transduction pathway requiring protein kinase C activation mediated by a pertussis-toxin-sensitive G-protein. As revealed by the use of antibodies directed against the different alpha-subunits expressed in portal vein myocytes, we show that the clonidine-induced stimulation of voltage-dependent Ca2+ channels is mainly mediated by a Gi1-2-protein.

Abstract:
Using subtype-selective agonists and antagonists, and antibodies directed against phosphatidylinositol and G-proteins, it has been shown in single myocytes of rat portal vein that both alpha 1A- and alpha 2A-adrenoceptors modulate Ca2+ channels through two distinct transduction pathways. alpha 1A-adrenoceptors couple with a Gq/G11 protein to activate a phospholipase C (PLC) which hydrolyses phosphatidylinositol to generate inositol 1,4,5-trisphosphate (InsP3) and diacylglycerol (DAG). InsP3 releases intracellular stored Ca2+ as evidenced by microspectrofluorimetry with Fura-2. The large and transient increase in [Ca2+]i activates chloride channels leading to a membrane depolarization that opens voltage-gated Ca2+ channels. In addition, DAG activates transiently protein kinase C (PKC) which increases the opening probability of Ca2+ channels through a phosphorylation-dependent process. alpha 2A-adrenoceptors do not induce Ca2+ release from intracellular stores but promote sustained Ca2+ influx through voltage-gated Ca2+ channels. The coupling involves a Gi-protein and activation of PKC by DAG. These two transduction pathways may be involved in the physiological action of noradrenaline in vascular smooth muscles.

Abstract:
The presence of functional alpha 2-adrenoceptors was investigated in isolated smooth muscle cells from rat portal vein using the nystatin-perforated patch-clamp technique. The free cytoplasmic calcium concentration ([Ca2+]i) was estimated using emission from the dye Fura-2. Activation of alpha 2-adrenoceptors by clonidine (an alpha 2-adrenoceptor agonist) or noradrenaline (a non-selective alpha-adrenoceptor agonist), both in the presence of 0.1 microM prazosin to block alpha 1-adrenoceptors, caused a slow and sustained increase in [Ca2+]i which was inhibited by 0.1 microM rauwolscine (an alpha 2-adrenoceptor antagonist). A similar Ca2+ response was obtained with oxymetazoline (a selective alpha 2A-adrenoceptor agonist) suggesting that the increase in [Ca2+]i resulted from activation of the alpha 2A-adrenoceptor subtype. The increase in [Ca2+]i did not occur in calcium-free solution or in the presence of oxodipine (a voltage-dependent calcium channel blocker), indicating that it depended on a calcium influx. The alpha 2A-adrenoceptor-activated calcium influx was unchanged after complete release of the stored calcium induced by applications of ryanodine and caffeine. In addition, no accumulation of inositol trisphosphate was detected in the presence of 0.1 microM prazosin. Taken together, these results indicate that alpha 2A-adrenoceptor activation does not stimulate phosphoinositide turnover and subsequent calcium release from intracellular stores. Whole-cell patch-clamp experiments showed that alpha 2A-adrenoceptor activation promoted calcium influx through voltage-dependent L-type channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract:
The effects of a novel dihydropyridine, elgodipine, and of three derivatives have been studied on the calcium channel currents of isolated cells from rat portal vein by the patch-clamp technique, and on specific (+)-[3H]isradipine binding to vascular membranes. Elgodipine inhibited both T- and L-type calcium channels in a concentration-dependent manner. Half-inhibitions of T- and L-type calcium channel current were obtained at concentrations of 32 and 2.3 nM, respectively. Currents activated repetitively were similarly inhibited than those after a rest period, indicating absence of use-dependent inhibition by elgodipine. When cells were held at depolarized membrane potentials at which T- or L-type calcium channels were inactivated, the inhibitory effects of elgodipine were enhanced on both calcium channel currents, indicating that the elgodipine-induced inhibition was voltage-dependent. The elgodipine concentration which blocked the inactivated calcium channels were 5 to 7 times lower than those which blocked the resting calcium channels. The inhibition constant for elgodipine obtained from the displacement of (+)-[3H]isradipine binding to the L-type calcium channels in vascular membranes was identical to the dissociation constant calculated from electrophysiological data on inactivated calcium channels. At concentrations that completely inhibited calcium channels, elgodipine had no effect on chloride and potassium channels, and did not interfere with the intracellular calcium stores.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract:
Previously, we have shown that myocytes from rat portal vein express alpha 1A-adrenoreceptors that couple with a Gq/G11-protein to stimulate phosphoinositide turnover and release of calcium from intracellular stores. The purpose of this study was to investigate the contribution of both alpha 1- and alpha 2-adrenoreceptor subtypes in inducing stimulation of voltage-operated calcium channels. Norepinephrine (a nonselective alpha-adrenoreceptor agonist), phenylephrine (an alpha 1-adrenoreceptor agonist), clonidine, and oxymetazoline (alpha 2-adrenoreceptor agonists) stimulated the calcium channel current by a similar extent. Using subtype-selective antagonists we showed that both alpha 1A- and alpha 2A-adrenoreceptors modulated voltage-operated calcium channels through two distinct transduction pathways. alpha 1A-Adrenoreceptors coupled with a pertussis toxin-insensitive G-protein whereas alpha 2A-adrenoreceptors coupled with a pertussis toxin-sensitive G-protein. Portal vein myocytes expressed G-proteins that were recognized by anti-alpha q/alpha 11, -alpha i(1-2), and -alpha i(3) antibodies. As internal applications of anti-phosphatidylinositol and anti-alpha q/alpha 11 antibodies had no effect on the alpha 2A-adrenoreceptor-induced enhancement of calcium channel current, these findings suggest that phosphatidylinositol hydrolysis and Gq/G11-protein are not involved in the alpha 2A-adrenoreceptor-induced coupling process. A protein kinase C inhibitor, GF 109203X, and a long term (24 h) treatment with phorbol dibutyrate to decrease the activity of protein kinase C blocked the alpha 1A- and alpha 2A-adrenoreceptor-induced stimulation of calcium channels as well as that stimulation induced by phorbol dibutyrate. Moreover, activation of alpha 2A-adrenoreceptors did not induce a significant calcium release from intracellular stores. These data suggest that two distinct G-proteins, probably Gq/G11 and Gi, coupled to alpha 1A- and alpha 2A-adrenoreceptors regulate calcium influx through voltage-operated calcium channels by two different transduction pathways leading to activation of protein kinase C.

Abstract:
We have previously reported that spatial reference memory (RM) training-induced

Abstract:
We studied the effects of the enantiomers of the dihydropyridine derivative, 4-(2,3 methylenedioxyphenyl)-1,4-dihydro-2,6-dimethyl-3 carboxyethyl-5-carboxymethyl-pyridine (oxodipine), on voltage-dependent Ca2+ channels of rat portal vein myocytes by combining electrophysiological techniques and binding studies. (+)- and (-)-oxodipine depressed the L-type Ca2+ current in a concentration-dependent manner, with similar IC50 values (around 10 nM) but had no appreciable effect on the intracellular Ca2+ stores. The steady-state inactivation curve for the Ca2+ current was shifted along the voltage axis to negative membrane potentials indicating that the block of the Ca2+ current by oxodipine enantiomers increased with depolarization. The voltage-dependent inhibitory property of oxodipine was related to an increase in [3H](+)-4-(benzo-2-oxa-1,3-diazol-4-yl)-1,4-dihydro-2,6-dimethy lpy ridine- 3,5-dicarboxylic acid 3-isopropyl, 5-methyl ester (isradipine) binding affinity without change in binding capacity. In normally polarized intact strips, interactions of (+)- and (-)-oxodipine with [3H](+)-isradipine binding indicated a stimulation of the radioligand binding at low concentrations of (-)-oxodipine while the (+) enantiomer seemed to act as a competitive ligand. Depolarization of intact strips with 135 mM K(+)-solutions increased the apparent affinity of the enantiomers of oxodipine, and abolished the stimulating effect of (-)-oxodipine on the binding of [3H](+)-isradipine. Inhibition of Ca2+ current was increased in the simultaneous presence of 1 nM of (+)- and (-)-oxodipine when compared to the inhibitions induced by 2 nM of each enantiomer.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract:
OBJECTIVE: The purpose of our study was to characterize the membrane mechanisms responsible for oxytocin-induced depolarization in single cells from pregnant rat myometrium. STUDY DESIGN: Membrane currents were recorded with the whole-cell mode of the standard patch-clamp technique. Intracellular calcium concentration was monitored with the fluorescence from Fura 2 added to the pipette solution. RESULTS: We found that oxytocin predominantly activates potassium, chloride, and cation conductances. Chloride and cation currents were evoked by an increase in the intracellular calcium concentration dependent on calcium release from the heparin-sensitive intracellular stores. Chloride and cation current showed different calcium dependences so that they could be activated separately. CONCLUSION: Stimulation of oxytocin receptors induces opening of calcium-activated chloride and cation channels, leading to depolarization of the myometrial cells. This depolarization opens, in turn, voltage-dependent calcium channels.

Abstract:
Intracellular free Ca2+ concentration ([Ca2+]i) was monitored using the fluorescence from the dye Fura-2-AM in single myometrial cells from pregnant rats. Oxytocin and acetylcholine applied to the cell evoked an initial peak in [Ca2+]i followed by a smaller sustained rise which was rapidly terminated upon removal of acetylcholine or persisted after oxytocin removal. A Ca2+ channel blocker (oxodipine) and external Ca2+ removal decreased both the transient and sustained rises in [Ca2+]i suggesting that Ca2+ influx through L-type Ca2+ channels participated in the global Ca2+ response induced by oxytocin. However, the initial peak in [Ca2+]i produced by oxytocin was mainly due to Ca2+ store release: it was abolished by inclusion of heparin [which blocks inositol 1,4,5-trisphosphate (InsP3) receptors] in the pipette (whole-cell recording mode of patch-clamp) and external application of thapsigargin (which blocks sarcoplasmic reticulum Ca(2+)-ATPases). In contrast, the transient Ca2+ response induced by oxytocin was unaffected by ryanodine. Moreover, caffeine failed to induce a rise in [Ca2+]i but reduced the oxytocin-induced transient Ca2+ response. The later sustained rise in [Ca2+]i produced by oxytocin was due to the entry of Ca2+ into the cell as it was suppressed in external Ca(2+)-free solution. The Ca2+ entry pathway is permeable to Mn2+ ions, in contrast to that described in various vascular and visceral smooth muscle cells. Oxytocin-induced Ca2+ release is blocked by the oxytocin antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT. The prolonged increase in [Ca2+]i after oxytocin removal is rapidly terminated by addition of the oxytocin antagonist suggesting that oxytocin dissociation from its receptor is very slow.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract:
It has been shown in numerous studies that memory testing can alter presynaptic

Abstract:
Intracellular free Ca++ concentration ([Ca++]i) was monitored using the fluorescence from the dye fura-2-acetoxymethylester in single myocytes from rat portal vein. In the presence of oxodipine (a L-type Ca++ channel inhibitor), norepinephrine (10 microM) evoked transient increases in [Ca++]i which were related to release of Ca++ from intracellular stores. The alpha-1 adrenoceptors mediating intracellular Ca++ release and inositol phosphate accumulation were identified by using subtype-selective agonists and antagonists. Pretreatment with chloroethylclonidine had little effect on the norepinephrine-induced increase in [Ca++]i and inositol phosphate accumulation. In contrast, prazosin, 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane and alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)ethyl)-amino )- propyl)benzeneacetonitrile fumarate produced a concentration-dependent inhibition of both intracellular Ca++ release and inositol phosphate accumulation. The rank of potency was prazosin > 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane > alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)ethyl)-amino - propyl) benzeneacetonitrile fumarate. Methoxamine was as effective as norepinephrine but was less potent as shown by the rightward shift of the concentration-response curves. These results indicate that myocytes from rat portal vein express alpha-1A adrenoceptors whose activation stimulates phosphoinositide turnover and release of Ca++ from intracellular stores. The alpha-1A adrenoceptor stimulation of [Ca++]i and subsequent activation of Ca(++)-activated Cl- current was insensitive to intracellular applications of pertussis toxin, but concentration-dependently blocked by intracellular dialysis with a pipette solution containing anti-alpha q/alpha 11 antibody (whole cell recording mode).(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract:
We studied the effects of six dihydropyridines on the specific binding of (+)-[3H]-isradipine to vascular (portal vein) and cardiac isolated membranes to achieve the relative cardiovascular selectivity of these compounds. Elgodipine, (+)-oxodipine and nifedipine had a significantly higher affinity for the vascular L-type calcium channel than for the cardiac calcium channel while nicardipine showed opposite properties. The other dihydropyridines (nitrendipine and (+)-isradipine) had similar affinities for the cardiac and vascular calcium channels. As the membrane potential of isolated membranes is about 0 mV, these results suggest that the differences in binding of these dihydropyridines to L-type calcium channels in vascular and cardiac cells may be attributed to differences in the molecular structure of these calcium channels.

Abstract:
Alterations in hippocampal cholinergic activity associated with different types

Abstract:
The effects of systemic administration of tianeptine, a new psychotropic agent

Abstract:
The spatial working memory performances of young (2 months) and aged (24-26

Abstract:
In order to test the hypothesis that alpha-noradrenergic receptors in the septum

Abstract:
Sodium-dependent high-affinity choline uptake velocities in P2 fractions of the

Abstract:
Evidence for different types of memory in mice may lead to development of animal

Abstract:
Possible differentiation of the intervention of cholinergic septohippocampal and