title: Contractile action of yohimbine in the dog basilar artery.
abstract: Yohimbine (10(-8) to 10(-4) M) produced a concentration-dependent contraction of the isolated dog basilar artery. The maximal amplitude of the contraction induced by yohimbine was approximately 50% of that induced by 5-hydroxytryptamine (5-HT) and twice as large as that of noradrenaline. This response to yohimbine (3 X 10(-7) M) was attenuated by 5-HT receptor antagonists such as 5-methoxygramine, methysergide and ketanserin. Phentolamine also antagonized the yohimbine response but prazosin and DG-5128 did not. The 5-HT antagonists and phentolamine produced similar inhibition of the response to 5-HT. Propranolol, atropine and diphenhydramine did not modify the contractile responses to yohimbine and 5-HT. These results suggest that the contractile response to yohimbine is mediated through 5-HT receptors. In addition to the contractile action, yohimbine at concentrations over 10(-6) M inhibited the contractile response to 5-HT. Thus, the possibility that yohimbine is a partial agonist on 5-HT receptors in the dog basilar artery has to be considered.
mesh_terms: D000818:Animals; D001488:Basilar Artery / Q000187:drug effects*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D009994:Osmolar Concentration; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014661:Vasoconstriction; D015016:Yohimbine / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D012702:Serotonin Antagonists; D015016:Yohimbine; D012701:Serotonin