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R Hen

Publications and source records attributed to R Hen.

At least 19 recordsLinked to original sources
PubMed1997

Adenovirus-mediated expression of 5-HT1B receptors in cardiac ventricle myocytes; coupling to inwardly rectifying K+ channels.

The 5-HT1B receptor is expressed on nerve terminals where it inhibits neurotransmitter release. When expressed ectopically in fibroblasts, the 5-HT1B receptor inhibits adenylyl cyclase. However, in the central nervous system, the effect of this receptor on neurotransmitter release appears to be cAMP-independent. We therefore investigated alternative effector systems that might be activated by the 5-HT1B receptor. We constructed a recombinant adenovirus that allows expression of high levels of the 5-HT1B receptor in a variety of cells. We chose cardiac ventricle myocytes because they express a muscarinic-gated, inwardly rectifying K+ channel (i[KACh]). In infected ventricle cells, both 5-HT and the muscarinic receptor agonist, carbachol, elicited a similar inwardly rectifying K+ current. The currents elicited by these agonists were pertussis-toxin sensitive and were not additive. These results suggest a common signal transduction pathway for 5-HT1B and muscarinic receptors in ventricle cells.

Adenoviridae↗
PubMed1997

Mutational analysis of the mouse 5-HT7 receptor: importance of the third intracellular loop for receptor-G-protein interaction.

The mouse serotonin (5-HT) receptor subtype, 5-HT7, belongs to the family of seven transmembrane G-protein-coupled receptors. To identify the structural basis for the coupling of 5-HT7 receptor to G alpha(s) we constructed a number of receptor mutants in which amino acid residues were either substituted or deleted from the second and third intracellular loops. Wild-type and mutant 5-HT7 receptors were expressed in insect cells using the baculovirus vectors. Two mutant receptor species, 5-HT7(E325G) and 5-HT7(K327S), demonstrated markedly impaired abilities to stimulate adenylyl cyclase. The results suggest the importance of the C-terminal region of the third intracellular loop in receptor-G-protein interaction and that specific charged residues, E325 and K327, may play a critical role in this interaction.

Animals↗
PubMed1997

Serotonin1B receptor modulation of startle reactivity, habituation, and prepulse inhibition in wild-type and serotonin1B knockout mice.

Two operational measures of central information processing mechanisms are habituation and prepulse inhibition (PPI) of the startle response. Both measures can be assessed reliably in humans and other animals, and have been shown to be deficient in patients with schizophrenia. The three present experiments assessed the involvement of the serotonin1B (5-HT1B) receptor in modulating startle reactivity, habituation, and PPI by comparing 5-HT1B receptor gene knockout (5-HT1B knockout) with wild-type 129/Sv mice. In experiment I, female mice received saline, 2.0 mg/kg 5-methoxy-3(1,2,3,6)tetrahydropyridin-4-yl-1H-indole (RU24969), a 5-HT1A/1B agonist, and 1.0 mg/kg 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT), a selective 5-HT1A agonist. Female mice received saline, 10.0 mg/kg RU24969, and 5.0 mg/kg 8-OH-DPAT in experiment 2, and male mice received saline, 10.0 mg/kg RU24969, and 5.0 mg/kg 8-OH-DPAT in experiment 3. All three studies used identical within-subjects designs. Two phenotypic differences were observed following saline treatment: 5-HT1B knockout mice consistently exhibited a small increase in PPI that achieved significance in experiment 1; and 5-HT1B knockout male mice exhibited robust decreases in startle reactivity. Habituation was disrupted consistently by RU24969 in wild-type but not in 5-HT1B knockout mice, while 8-OH-DPAT had no effect on habituation. Consistent with the phenotypic difference in PPI, the high dose of RU24969 significantly and consistently reduced PPI in wild-type but not in 5-HT1B knockout mice. 8-OH-DPAT increased PPI in both wild-type and 5-HT1B knockout mice in every experiment. These findings suggest that 5-HT1B receptors modulate startle reactivity, habituation, and PPI in mice. Additionally, a potential species difference may exist in the behavioral effects of 5-HT1A receptor activation on PPI.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1997

Intravenous cocaine self-administration in mice lacking 5-HT1B receptors.

The present experiment tested the hypothesis that 5-HT1B receptors are involved in the reinforcing effects of cocaine. Transgenic mice lacking 5-HT1B receptors were used as subjects and compared with wild-type mice for the acquisition and maintenance of intravenous (IV) cocaine self-administration. Male 129/Sv-ter and 5-HT1B-minus 129/Sv-ter inbred mice (Columbia University, New York) were initially trained to press a lever under a fixed-ratio schedule 2, first for sweetened condensed milk as reinforcer and subsequently for cocaine (2.0 mg/kg/infusion). When a stable baseline of responding was obtained, each subject was tested under different doses of cocaine (1.0, 2.0, and 4.0 mg/kg), with the number of reinforcers per hour used as the dependent variable. Both strains successfully acquired food-shaping and cocaine self-administration, but the mutant mice presented a significantly shorter latency to meet IV cocaine self-administration acquisition criteria (p < 0.05). However, both wild-type and mutant mice had similar dose-response to cocaine. These results suggest that the 5-HT1B receptors may be implicated in the propensity to self-administer cocaine, but other mechanisms might be involved in the maintenance of cocaine self-administration.

Animals↗
PubMed1997

In vitro induction of apoptosis or differentiation by dopamine in an immortalized olfactory neuronal cell line.

A new neuronal cell line was generated by transfection of rat olfactory epithelium with immortalizing recombinant oncogene E1A of adenovirus-2. The resulting 13.S.1.24 line of transformed cells expressed an antigenic phenotype of olfactory neuronal progenitors. Addition of dopamine to 13.S.1.24 cultures induced reduction of cell number within 2 days. Two hallmarks of apoptosis were detected in dopamine-treated cultures: internucleosomal DNA fragmentation and nuclear condensation. Dopamine did not alter the cell proliferation rate, as assessed by [3H]thymidine incorporation. Dopamine also stimulated differentiation of surviving 13.S.1.24 cells into bipolar olfactory marker protein-immunoreactive neurons. Time-dependency assessments over 1 week of treatment indicated that apoptosis and differentiation induced by dopamine were concomitant. Both apoptosis and differentiation triggered by dopamine were dose-dependent, half-maximal effects being obtained with approximately 10 microM dopamine. Mediation of both effects by dopaminergic D2 receptors was supported by several observations: active dopamine doses in micromolar ranges, quinpirole agonism and eticlopride antagonism, D2-characteristic rank order of potency among the three agonists tested, and specific binding of a selective D2-like radioligand to 13.S.1.24 cells. The present data altogether indicated that dopamine commits immortalized olfactory neuronal cells in vitro either to apoptosis or to olfactory-like differentiation via D2 dopaminergic receptors.

Adenoviridae↗
PubMed1997

Regulation of serotonin release in the frontal cortex and ventral hippocampus of homozygous mice lacking 5-HT1B receptors: in vivo microdialysis studies.

To assess the involvement of the serotonin receptor subtype 5-HT1B as terminal autoreceptor regulating 5-HT release in mice, we compared basal values and potassium-evoked changes of extracellular 5-HT levels obtained by in vivo microdialysis in two serotoninergic terminal projection areas of conscious wild-type mice with those measured in homozygous mutant mice lacking the gene encoding the 5-HT1B receptor. In the frontal cortex and ventral hippocampus, basal and K+-evoked 5-HT release did not differ between the two strains of mice studied. The infusion via reverse microdialysis of the selective 5-HT1B receptor agonist CP-93,129 (500 nM) decreased significantly K+-evoked 5-HT release in the frontal cortex (by -44%) and ventral hippocampus (by -32%) of wild-type mice but had no effect in mutants. In a similar manner, the mixed 5-HT1B-5-HT1D receptor agonist sumatriptan (800 nM) decreased significantly K+-evoked 5-HT release in the frontal cortex (by -46%) of wild-type mice but had no effect in mutants. These results demonstrated that 5-HT1B knockout mice are not as sensitive to full (CP-93,129) and mixed (sumatriptan) 5-HT1B receptor agonists as are wild-type mice. These data provide in vivo evidence that, in mice, 5-HT1B, but not 5-HT1D, autoreceptors inhibit 5-HT release at nerve terminals located in the frontal cortex and ventral hippocampus.

Animals↗
PubMed1997

5-Hydroxytryptamine1B receptors modulate the effect of cocaine on c-fos expression: converging evidence using 5-hydroxytryptamine1B knockout mice and the 5-hydroxytryptamine1B/1D antagonist GR127935.

Serotonergic transmission has been suggested to modulate the effects of cocaine. However, the specific receptors and brain structures underlying this phenomenon have not been identified. To test the possible contribution of the 5-hydroxytryptamine1B (5-HT1B) receptor, we studied the induction of the immediate-early gene c-fos elicited by cocaine in knockout mice lacking this receptor. 5-HT1B knockout mice display a markedly reduced effect of cocaine on c-fos induction in different brain structures, most notably in the striatum. In addition, the administration to wild-type mice of the 5-HT1B receptor agonist RU24969 results in a striatal induction of c-fos expression very similar to that induced by cocaine in its time course, cellular and anatomical distribution, and pharmacology. Here, we also report the ability of a 5-HT1D receptor antagonist, GR127935, to antagonize 5-HT1B receptors in vivo. Finally, when administered to wild-type mice, GR127935 reduces the increase in striatal c-fos expression elicited by cocaine. These converging lines of evidence obtained with the knockout mice and 5-HT(1B/1D) antagonist indicate that cocaine acts as an indirect agonist of 5-HT1B receptors in vivo and demonstrate that activation of 5-HT1B receptors contributes to the cellular responses elicited by cocaine.

Animals↗
PubMed1996

Functional characterisation of the Drosophila 5-HTdro1 and 5-HTdro2B serotonin receptors in insect cells: activation of a G(alpha) s-like protein by 5-HTdro1 but lack of coupling to inhibitory G-proteins by 5-HTdro2B.

Insect cells are routinely used for the production of receptor proteins. Expression of the Drosophila 5-HTdro1 serotonin receptor resulted in positive coupling of the receptor to adenylyl cyclase via the G(alpha)s G-protein subtype. The Drosophila 5-HTdro2B receptor stimulated the metabolism of inositol phospholipid via a pertussis toxin-insensitive G-protein, but exhibited no detectable inhibition of adenylyl cyclase. Immunoblot analysis of the endogenous G-proteins revealed that Sf9 cells lack the G-protein subtypes G(alpha i 1-3) and G(alpha)o, but express the subtype G(alpha)s and G(alpha)q.

Animals↗
PubMed1996

5-HT1B receptor knock out--behavioral consequences.

Serotonin is a neuromodulator that is involved in a number of mood disorders such as depression, anxiety and impulsive violence. In an attempt to dissect the contribution of individual 5-HT receptor subtypes to behavior, we have generated by homologous recombination, mutant mice lacking the 5-HT1B receptor. These mice did not exhibit any obvious developmental or behavioral defect. However, the hyperlocomotor effect of the 5-HT1A/1B agonist, RU 24969 was completely absent in mutant mice, indicating that this effect is mediated by 5-HT1B receptors. Moreover, when confronted with an intruder, isolated mutant mice attacked the intruder faster and more intensely than wild-type mice, suggesting an involvement of 5-HT1B receptors in the modulation of aggressive behavior. These data might be related to the fact that a class of 5-HT1 agonists, termed serenics, have anti-aggressive properties, and with the findings that certain impulsive aggressive behaviors are associated with deficits in central serotonin.

Aggression↗
PubMed1996

Mean genes.

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Aggression↗
PubMed1996

Elevated alcohol consumption in null mutant mice lacking 5-HT1B serotonin receptors.

Substantial evidence links alcohol drinking and serotonin (5-HT) functioning in animals. Lowered central 5-HT neurotransmission has been found in a subgroup of alcoholics, possibly those with more aggressive, assaultive tendencies. Several rodent studies have also suggested that intact 5-HT systems are important determinants of sensitivity and/or tolerance to ethanol-induced ataxia and hypothermia. Null mutant mice lacking the 5-HT1B receptor gene (5-HT1B-/-) have been developed that display enhanced aggression and altered 5-HT release in slice preparations from some, but not all, brain areas. We characterized these mice for sensitivity to several effects of ethanol. Mutant mice drank twice as much ethanol as wild-type mice, and voluntarily ingested solutions containing up to 20% ethanol in water. Their intake of food and water, and of sucrose, saccharin and quinine solutions, was normal. Mutants were less sensitive than wild-types on a test of ethanol-induced ataxia and, with repeated drug administration, tended to develop tolerance more slowly. In tests of ethanol withdrawal and metabolism, mutants and wild-type mice showed equivalent responses. Our results suggest that the 5-HT1B receptor participates in the regulation of ethanol drinking, and demonstrate that serotonergic manipulations lead to reduced responsiveness to certain ataxic effects of ethanol without affecting dependence.

Alcohol Drinking↗
PubMed1996

5-Carboxamido-tryptamine, CP-122,288 and dihydroergotamine but not sumatriptan, CP-93,129, and serotonin-5-O-carboxymethyl-glycyl -tyrosinamide block dural plasma protein extravasation in knockout mice that lack 5-hydroxytryptamine1B receptors.

We studied the dural plasma protein extravasation response after unilateral electrical stimulation of the trigeminal ganglion in mice lacking serotonin 5-HT1B (5-HT1D beta) receptors by modifying a technique previously described in rats or guinea pigs. We investigated the inhibitory effects of six 5-HT1 receptor agonists in this model: 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2-b]pyrid-5-one (CP-93,129), sumatriptan, serotonin-5-O-carboxymethyl-glycyl -tyrosinamide (GTI), 5-methylaminosulfonylmethyl-3-(N-methylpyrrolidin-2R -ylmethyl)-1H-indole (CP-122,288), 5-carboxamido-tryptamine (5-CT), and dihydroergotamine. The plasma extravasation response did not differ between wild-type and mutant after vehicle injection. The potency of sumatriptan, CP-122,288, CP-93,129, and 5-CT in wild-type mice was similar to that previously reported for rats. CP-122,288 (1 nmol kg), 5-CT (1 nmol/kg), and dihydroergotamine (72 nmol/kg) inhibited plasma protein extravasation within dura mater after electrical trigeminal ganglion stimulation in both wild-type and knockout mice, which suggests that these agonists act predominantly via receptors other than 5-HT1B. Unlike the wild-type mice, CP-93,129 (1.4 mumol/kg), a specific 5-HT1B receptor agonist, had no effect in knockout mice. The same held true for sumatriptan (0.7 mumol/kg) and GTI (0.6 mumol/kg). These results suggest that CP-93,129, sumatriptan, and GTI exert their effects via 5-HT1B (5-HT1D beta) receptors in mice.

Animals↗
PubMed1996

5-hydroxytryptamine-moduline, a new endogenous cerebral peptide, controls the serotonergic activity via its specific interaction with 5-hydroxytryptamine1B/1D receptors.

The serotonergic system controls the activity of neurotransmissions involved in numerous physiological functions. It is also thought to be crucially implicated in various pathologies, including psychiatric disorders such as depression, anxiety, and aggressiveness. The properties of 5-hydroxytryptamine (5-HT)-moduline, a novel endogenous peptide, have been tested in vitro and in vivo. Binding studies have shown that the peptide specifically interacts with 5-HT1B/1D receptors via a noncompetitive mechanism corresponding to a high apparent affinity (EC50 = 10(10) M). The interaction was shown in rat and guinea pig brain tissues and in cells transfected with either 5-HT1B or 5-HT1D beta receptor gene. [3H]5-HT-moduline binds to a single population of sites in mammalian brain (Kd = 0.4 nM in rat, Kd = 0.8 nM in guinea pig) as well as in transfected cells expressing the 5-HT1B or the 5-HT1D beta receptors (Kd = 0.2 and 0.6 nM, respectively). Furthermore, the binding is clearly specific of the LSAL sequence. Autoradiographic studies showed an heterogeneous brain distribution of this site. The interaction of 5-HT-moduline with the 5-HT1B/1D receptor corresponds to a decrease in the functional activity of the receptor (i.e., a decrease in the inhibitory effect of a 5-HT1B agonist on the evoked release of [3H]5-HT from synaptosomal preparation). It was also shown that 5-HT-moduline possess an in vivo effect in the social interaction test in mouse. Finally, it was demonstrated that 5-HT-moduline was released from brain synaptosomal preparation by a K+/Ca(2+)-dependent mechanism. In conclusion, 5-HT-moduline is a novel endogenous peptide regulating the serotonergic activity via a direct action at presynaptic 5-HT receptor. It may play an important role in the physiological mechanisms involving the serotonergic system, particularly in mechanisms corresponding to the elaboration of an appropriate response of the central nervous system to a given stimulus.

Animals↗
PubMed1995

Regulation of [3H]5-HT release in raphe, frontal cortex and hippocampus of 5-HT1B knock-out mice.

Regulation of the electrically evoked release of [3H]5-HT was examined in midbrain, frontal cortex and hippocampus preloaded slices obtained from wild-type and 5-HT1B knock-out mice. In the absence of any drug [3H]5-HT released was increased in midbrain and hippocampus but not in frontal cortex slices of [3H]5-HT1B knock out mice. The selective 5-HT1B agonist CP 93129 and the 5-HT1B/1D agonist sumatriptan, inhibited [3H]5-HT release in hippocampus and cortical slices obtained from control mice but had no effect in mutants. In the two projection areas studied, the non-selective 5-HT agonist 5-carboxyamidotryptamine (5-CT) inhibited [3H]5-HT release in both groups of mice, indicating that additional 5-HT receptors, other than 5-HT1B, might be involved in the regulation of [3H]5-HT release from 5-HT terminals. In slices containing midbrain raphe nuclei, CP 93129 had no effect in either group. In contrast, sumatriptan inhibited [3H]5-HT release in controls and mutants. The latter effect was blocked by the 5-HT1D antagonist GR 127935, but not the 5-HT1A antagonist (+)WAY 100135, thus suggesting that a 5-HT1D-like receptor, possibly 5-HT1D alpha, negatively regulates 5-HT release in mouse midbrain raphe nuclei.

Animals↗
PubMed1995

Production and characterization of an antibody directed against the mouse 5HT1B receptor.

We have developed a polyclonal antibody directed against a peptide located in the third intracellular loop of the 5HT1B receptor. Its characterization was carried out using NIH cells stably transfected with a eukaryotic expression vector containing the mouse 5HT1B receptor cDNA. The synthetic antigenic peptide had a unique sequence to the mouse 5HT1B receptor corresponding to amino acids 273-287 localized in the third intracellular loop. In dot blot analysis, antisera detected 2 ng to 2 micrograms of synthetic peptide at dilutions of 1/200-1/20,000 and bound antibody was visualized using an immunoperoxidase procedure. Preimmune serum showed no immunoreactivity to the synthetic peptide. NIH cells stably transfected expressing mouse 5HT1B receptor displayed an intense immunoreactivity with the antiserum. In contrast no immunoreactivity was seen in any of the control experiments. In the present study, we have produced a specific antibody which is an essential tool suitable for immunocytochemical applications such as regional distribution, anatomical localization and phenotypical characterization of the cells expressing the 5HT1B receptors in brain by double immunolabelling procedure.

Amino Acid Sequence↗
PubMed1995

New players in the 5-HT receptor field: genes and knockouts.

In recent years, cloning has revealed the existence of no less than 14 mammalian 5-HT receptors, as well as evidence that isoforms of the 5-HT4 and 5-HT7 receptors are generated by alternative splicing. In addition, molecular biology techniques have provided new tools with which to study the function of 5-HT receptors. For example, new technologies are emerging that will allow the generation of either inducible or tissue-specific knockouts (or both). In this review José Lucas and René Hen focus on the characteristics of the most recently cloned receptors and the contribution of molecular biology to the understanding of 5-HT receptor function.

Animals↗