Physostigmine- and 1,1-dimethyl-4-phenylpiperazinium-induced pressor responses and catecholamine release in 6-hydroxydopamine-treated rats

Abstract

In urethane-anaesthetized rats, physostigmine and 1,1-dimethyl-4-phenylpiperazinium (DMPP) markedly increased the adrenal catecholamine output in normal and in 6-hydroxydopamine-treated rats. Pretreatment with 6-hydroxydopamine did not interfere with the release of catecholamines follwing physostigmine and DMPP whereas the blood pressure responses were substantially blocked. A similar block in the pressor response was seen in animals in which demudullation had been performed prior to giving 6-hydroxydopamine. 6-Hydroxydopamine pretreatment enhanced the pressor effect of noradrenaline. It is concluded that increases in the catecholamine output do not contribute to the pressor effects either DMPP or physostigmine.