5-HT1B receptors modulate release of [3H]dopamine from rat striatal synaptosomes: further evidence using 5-HT moduline, polyclonal 5-HT1B receptor antibodies and 5-HT1B receptor knock-out mice.
In previous paper based on classical pharmacological tools, we identified a Gi protein-coupled presynaptic 5-hydroxytryptamine (5-HT) 1B receptor causing inhibition of dopamine (DA) release in rat striatal synaptosomes. It was the aim of the present study to further explore this receptor, using 5-HT moduline, a polyclonal antibody directed against 5-HT1B receptors and 5-HT1B receptor knock-out mice. Preincubation of rat striatal synaptosomes with 5-HT moduline (0.1, 1, or 10 microM) significantly reduced the inhibitory effect of CP93,129, a selective rat 5-HT1B receptor agonist, on K+-evoked overflow of [3H]DA in a non-competitive manner: 5-HT moduline did not modify the IC50 of CP93,129, but concentration-dependently reduced the maximal inhibitory effect. Preincubation of rat striatal synaptosomes with a specific polyclonal 5-HT1B receptor antibody also resulted in a significant attenuation of the inhibitory effect of CP93,129 on K+-evoked overflow of [3H]DA. In female 129/Sv wild-type mice, CP93,129 and 5-carboxyamidotryptamine maleate (5-CT), a non-selective 5-HT1B receptor agonist, inhibited the K+-evoked [3H]DA overflow in a concentration-dependent manner. Sumatriptan, a selective rat 5-HT1D receptor agonist, did not modify the overflow of [3H]DA. SB224289, a selective 5-HT1B receptor antagonist, abolished the inhibitory effects of CP93,129 and 5-CT. The inhibitory effects of CP93,129 and 5-CT were absent in synaptosomes from 5-HT1B receptor knockout mice. No compensatory inhibition effect in mutant mice was observed using sumatriptan. In conclusion, the results show that a non-competitive antagonist of the 5-HT1B receptor concentration-dependently decreases the maximal inhibitory effect of a 5-HT1B receptor agonist on the synaptosomal K+-evoked release of [3H]DA in striatum. Moreover, a specific antibody raised against the receptor and particularly directed against a region of the receptor protein involved in signal transduction, namely the coupling with the G-protein, also antagonizes the inhibitory effect of the stimulation of 5-HT1B receptor on the release of [3H]DA. Ultimately the disruption of 5-HT1B receptor gene in 5-HT1B knock-out mice leads to a total suppression of the effect of 5-HT1B receptor agonists on [3H]DA release. These observations further support our previous observations using selective agonists/antagonists, indicating that 5-HT1B receptors control the release of neuronal DA as presynaptic heteroreceptors.
Sarhan
H
H
Unité de Pharmacologie Neuro-Immuno-Endocrinienne, Institut Pasteur, Paris, France.
Grimaldi
B
B
Hen
R
R
Fillion
G
G
D000595:Amino Acid Sequence; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology*; D000918:Antibody Specificity; D004298:Dopamine / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D017072:Neostriatum / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism*; D010881:Piperidones / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013141:Spiro Compounds / Q000494:pharmacology; D013574:Synaptosomes / Q000378:metabolism*
C102005:5-HT-moduline; D019138:Antibodies, Blocking; D009479:Neuropeptides; D009842:Oligopeptides; D010881:Piperidones; D011725:Pyridines; D011758:Pyrroles; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; C108518:SB 22489G; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013141:Spiro Compounds; C065046:3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo(3,2-b)pyrid-5-one; D004298:Dopamine