Dopamine may be a neurohormone in rat adrenal cortex

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Abstract
In the periphery, dopamine (DA) is a precursor for norepinephrine (NE) and epinephrine (EPI) biosynthesis and is itself a neurotransmitter in sympathetic ganglia. In addition, DA may function as a neurohormone in providing maximum tonic inhibition of aldosterone secretion from the adrenal cortex. We have quantified the catecholamine content of the adrenal gland and have examined factors that regulate DA content of the adrenal cortex. Adult male Sprague-Dawley rats were assigned to one of four groups: adrenal demedullated (ADM); adrenal denervated via splanchnic nerve section (ADN); adrenal demedullated-denervated (DMN); and sham-operated controls (Sham). Ten days after surgery, rats were killed by decapitation, and the adrenals were removed and later assayed for catecholamine content. Compared with Sham, ADM and DMN decreased NE and EPI levels by 92–99% but DA levels by only 57–58%. ADN decreased levels of each catecholamine by 18–26%. These findings indicate that the adrenal cortex contains approximately 40% of the total gland content of DA and less than 8% of the total gland content of NE and EPI. Furthermore, DA in the adrenal cortex does not appear to require an intact splanchnic nerve supply to the adrenal. In a second experiment, we examined the effects of inhibition of catecholamine biosynthesis with alpha-methyl-p-tyrosine (alpha-MPT) on DA content in Sham and ADM rats. In Sham rats, alpha-MPT decreased adrenal DA by 44% and heart NE by 37%. In contrast, treatment of ADM rats with alpha-MPT increased adrenal DA by 49% but decreased heart NE by 36%.(ABSTRACT TRUNCATED AT 250 WORDS)