Quipazine-induced hypertension in anaesthetized cats is mediated by central and peripheral 5-HT2 receptors: role of the ventrolateral pressor area.
Quipazine (0.5 mg/kg i.v.) produced a sustained pressor response and an increase in splanchnic nerve activity in intact as well as in baroreceptor-denervated cats without causing a significant change in heart rate. These effects were prevented by the 5-HT2 receptor antagonists, ritanserin (0.5 mg/kg i.v.) or BW 501 C (0.5 mg/kg i.v.). Quipazine induced an hypertensive response and an increase in splanchnic discharge in cats pretreated with prazosin (0.1 mg/kg) or hexamethonium (10 mg/kg i.v.). Bilateral application of quipazine (25 micrograms/side) to the ventrolateral pressor area produced a rapid increase in mean blood pressure and in splanchnic discharge. Pretreatment with prazosin (0.1 mg/kg i.v.) abolished the hypertension but not the sympatho-excitatory effects of quipazine. Local application of the 5-HT2 receptor antagonists, LY53857 (10 micrograms/side) or cyproheptadine (10 micrograms/side), had no effects on blood pressure and splanchnic nerve activity but prevented or reversed the actions of locally applied quipazine. LY 53857 (10 micrograms/side) antagonized the sympatho-excitatory effects of systemically administered quipazine. These results indicate that the cardiovascular changes induced by quipazine in anaesthetized cats are mediated by central 5-HT2 receptors located in the ventrolateral pressor area and by peripheral vascular 5-HT2 receptors.
Vayssettes-Courchay
C
C
Institut de Recherches Servier, Suresnes, France.
Bouysset
F
F
Verbeuren
T J
TJ
Laubie
M
M
Schmitt
H
H
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003533:Cyproheptadine / Q000494:pharmacology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D006973:Hypertension / Q000139:chemically induced* / Q000503:physiopathology; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D010424:Pentobarbital; D011224:Prazosin / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology; D011814:Quipazine / Q000494:pharmacology*; D011985:Receptors, Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013153:Splanchnic Nerves / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects; D014630:Vagus Nerve / Q000502:physiology
D006584:Hexamethonium Compounds; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D003533:Cyproheptadine; D018738:Hexamethonium; D011814:Quipazine; D010424:Pentobarbital; D011224:Prazosin