Neurotransmitter interaction in regulation of adrenocortical ornithine decarboxylase.

Administration of the dopamine receptor agonists apomorphine (APM) and piribedil increases adrenocortical ornithine decarboxylase (ODC) activity. In this paper alterations in the sympathoadrenal system, and in the central dopaminergic and serotonergic systems have been produced to study the possible mechanism of action of APM on adrenocortical ODC. Unilateral splanchnicotomy, unilateral rhizotomy, and bilateral demedullation each attenuated the response of adrenocortical ODC to APM. Intracerebroventricular 6-hydroxydopamine and 5,6-dihydroxytryptamine, intraperitoneal p-chlorophenylalanine and electrolytic lesion of the medial raphe nucleus reduced the APM-induced increase. None of these treatments produced any changes in the endogenous ODC activity of the adrenal cortex. It is postulated that dopaminergic brain structures participate directly in the stimulatory effect on the hypophyseo-adrenal system to increase adrenocortical ODC activity. An intact central serotonergic system seems to be necessary for APM to exert its effect on adrenocortical ODC activity, particularly the medial raphe nucleus.