Effects of Diltiazem on Norepinephrine-, Phenylephrine- and Clonidine-induced Pressor Response in Rabbits

가토(家兎)에서 Norepinephrine, Phenylephrine 및 Clonidine의 승압반응(昇壓反應)에 대한 Diltiazem의 영향(影響)

To examine the selectivity of diltiazem, used in the cardiovascular diseases, on alpha-1 and alpha-2 adrenoceptor-induced pressor responses, effect of diltiazem on alpha-adrenocepter agonist-induced pressor responses were investigated in urethane-anesthetized rabbits and spinal rabbits. The results are summarized as follows: 1. Intravenous diltiazem(10, 30, 100, 300, $1000{\mu}g/kg$) produced dose-dependent depressor response in rabbits. 2. Pressor responses to intravenous norepinephrine($10{\mu}g/kg$) and phenylephrine ($30{\mu}g/kg$) were inhibited by pretreatment with intravenous diltiazem in rabbits and no difference was noted between the degree of both inhibitions of the pressor response by diltiazem. 3. Presser responses to intravenous norepinephrine ($3{\mu}g/kg$), phenylephrine ($20{\mu}g/kg$) and clonidine ($300{\mu}g/kg$) were inhibited by pretreatment with intravenous diltiazem in spinal rabbits. No difference was noted between the inhibition of norepinephrine-induced pressor response and that of phenylephrine-induced pressor response by diltiazem. The inhibition of clonidine-induced pressor response by diltiazem was slightly prominent than that of norepinephrine- or phenylephrine-induced pressor response. These results suggest that diltiazem significantly inhibits both pressor responses mediated by alpha-1 and alpha-2 adrenoceptors.