Alpha-adrenolytic properties of apogalanthamine and azapetine analogs.

Selectivities were examined between alpha 1 and alpha 2-adrenolytic activities of two apogalanthamine analogs (dibenzazocine derivatives), 6-methyl-5,6,7,8-tetrahydrodibenz[c,e]-azocine (DA-VIII-Me) and its N-allyl analog (DA-VIII-allyl), and two dibenzazepine derivatives, azapetine (DA-VII-allyl) and its N-methyl analog (DA-VII-Me). The alpha-adrenolytic activities were evaluated as inhibitory effects against the response to norepinephrine of isolated vas deferens and anococcygeus muscle of rats. The pA2 values for DA-VIII-Me, DA-VIII-allyl, DA-VII-Me and azapetine on the isolated rat vas deferens were 7.32, 7.76. 6.61 and 7.78 respectively, which were similar to those on the anococcygeus muscle. The alpha 2-adrenolytic activities of these compounds against the twitch-inhibitory response to clonidine in transmurally stimulated rat vas deferens and guinea-pig ileum were less potent than those against the above alpha 1-adrenoceptors. In addition, their inhibitory activities on the aggregation of human platelets induced by norepinephrine were weaker than those of phentolamine and yohimbine. These results indicate that the apogalanthamine and azapetine analogs tested are more selective in blocking alpha 1-adrenoceptors than alpha 2-adrenoceptors.