Effects of verapamil on norepinephrine-, phenylephrine- and clonidine-induced pressor response in rabbits and rats
1988
Shin, D.H. (Chonnam National Univ., Kwangju (Korea R.). Coll. of Veterinary Medicine) | Choi, S.H. (Chonnam National Univ., Kwangju (Korea R.). Coll. of Pharmacy)
To examine the selectivity of verapamil, used in the cardiovascular diseases, on alpha-1 and alpha-2 adrenoceptor-induced pressor responses, effects of verapamil on alpha-adrenoceptor agonist-induced pressor responses were investigated in urethane-anesthetized rabbits, spinal rabbits, rats and pithed rats. To evaluate the effects of verapamil on each pressor response induced by norepinephrine, phenylephrine and clonidine, these agonists were previously injected into an ear vein, and the same procedures were performed 1-2 min after treatment with intravenous verapamil. Intravenous verapamil produced dose-dependent depressor response in rabbits and rats. Pressor responses to intravenous norepinephrine (10 micro g/kg) and phenylphrine (30 micro g/kg) were inhibited by pretreatment with intravenous verapamil in rabbits and no difference was noted between the degree of both inhibitions of the pressor response by verapamil. Pressor responses to intravenous norepinephrine (3 micro g/kg), phenylephrine (20 micro/kg) and clonidine (300 micro g/kg) were inhibited by pretreatment with intravenous verapamil in spinal rabbits. No difference was noted between the inhibition of norepinephrine-induced pressor response and that of phenylephrine-induced pressor response by verapamil. The inhibition of clonidine-induced pressor response by verapamil was more prominent than that of norepinephrine- or phenylephrine-induced pressor response. Pressor responses to intravenous norepinephrine (3 micro g/kg) and phenylephrine (10 micro g/kg) were inhibited by pretreatment with intravenous verapamil in rats and no difference was noted between the degree of both inhibitions of the pressor response by verapamil
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