title: [Action of dihydroergocristine at pre- and postsynaptic alpha-adrenoceptors in the rat isolated vas deferens].
abstract: 1. The action of dihydroergocristine at pre- and postsynaptic alpha-adrenoceptors has been studied in the rat isolated vas deferens. 2. Postsynaptic alpha-adrenoceptor antagonist activity was assessed by comparing cumulative noradrenaline and phenylephrine dose-response curves in the absence and in the presence of increasing concentrations of antagonist. 3. Presynaptic alpha-adrenoceptor activity was assessed by studying the effects of drugs on contractions induced by electrical stimulation of the rat vas deferens. 4. At postsynaptic alpha-adrenoceptor dihydroergocristine antagonized the contraction induced by noradrenaline and phenylephrine with competitive mechanism (pA2 = 7.78 towards noradrenaline; pA2 = 7.76 towards phenylephrine). 5. At presynaptic alpha-adrenoceptors dihydroergocristine acts as partial agonist (pD2 = 5.70).
mesh_terms: D000316:Adrenergic alpha-Agonists; D000818:Animals; D004088:Dihydroergotoxine / Q000494:pharmacology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D000316:Adrenergic alpha-Agonists; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine; D010656:Phenylephrine; D009638:Norepinephrine
vernacular_title: Activité de la dihydroergocristine sur les alpha-adrénorécepteurs pré- et postsynaptiques du canal déférent isolé de rat.