Effects of quipazine on pre- and postsynaptic serotonin receptors: single cell studies in the rat CNS.
Many behavioural and biochemical studies have pointed to an agonistic activity of quipazine on serotonin (5-HT) receptors. In the present electrophysiological study, the effect of quipazine on pre- and postsynaptic 5-HT receptors in the rat was studied. Quipazine, administered intravenously, depressed the firing rate of 5-HT-containing dorsal raphe neurones (ED50 = 0.82 mg/kg). Microiontophoretic applications of quipazine on 5-HT-containing neurones in the dorsal raphe and on neurones of two forebrain regions receiving a 5-HT input (the ventral lateral geniculate nucleus and the dorsal hippocampus) consistently depressed neuronal firing rate as did 5-HT and D-lysergic acid diethylamide (LSD). Quipazine was more potent on 5-HT neurones than on the ventral lateral geniculate nucleus and hippocampal neurones: the post/presynaptic efficacy ratio for quipazine was similar to that of LSD. Following a selective denervation of 5-HT neurones with intraventricular injection of 5,7-di-hydroxy-tryptamine in desipramine-pretreated rats, the responsiveness of neurones in the ventral lateral geniculate nucleus to quipazine, applied microiontophoretically, was increased as was that to 5-HT and to LSD. These results provide direct evidence for the agonistic activity of quipazine on both pre- and postsynaptic 5-HT receptors.
D000818:Animals; D001921:Brain / Q000187:drug effects*; D007478:Iontophoresis / Q000379:methods; D008238:Lysergic Acid Diethylamide / Q000494:pharmacology; D008297:Male; D011804:Quinolines / Q000494:pharmacology*; D011814:Quipazine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology
D011804:Quinolines; D011985:Receptors, Serotonin; D012701:Serotonin; D011814:Quipazine; D008238:Lysergic Acid Diethylamide