[Pharmacologic study of several alpha-adrenolytics].

Six alpha-adrenoceptor blocking agents have been investigated in dogs and rats. 170 150 and 170 153 have been found the most potent of these agents. At low doses (0,1 microgram/kg) they reversed the pressor response to low doses of adrenaline (0,1 and 0,3 microgram/kg) and suppressed the response to high doses of adrenaline. They reduced the pressor response to noradrenaline. In addition, in dogs 170 150 increased the tachycardia caused by stimulation of the cardiac nerve. The compound prevented and reversed the inhibition caused by clonidine on the effects of cardiac nerve stimulation. 170 153 did not increase the tachycardia caused by cardiac nerve stimulation, but it prevented and reversed the inhibitory effects of clonidine on this stimulation. The results show that 170 150 and 170 153 are potent alpha-adrenoceptor blocking agents acting on both pre and post-synaptic alpha-adrenoceptors which could be interesting pharmacological tools.