Influence of pargyline on the effects of dopamine infusions on sympathetically innervated tissues

Abstract

Pretreatment of cats with the monoamine oxidase inhibitor, pargyline HCl, potentiated both the sympathomimetic effects of intravenous dopamine infusions and the inhibitory effects of these infusions on the responses of the spleen and nictitating membrane to nerve stimulation. The potentiation of the inhibitory effects was not associated with an increase in the dopamine content, nor a decrease in the noradrenaline content, of the spleen, but was accompanied by an increase in the dopamine-noradrenaline ratio of the sympathetic transmitter released following nerve stimulation. The possible significance of these findings is discussed in the context of the hypothesis that the antihypertensive effects of monoamine oxidase inhibitors may be partially mediated through the involvement of dopamine as a “false” neurochemical transmitter.