INDIRECT EVIDENCE TO SUGGEST THAT PROLACTIN MEDIATES THE ADRENAL ACTION OF HALOPERIDOL TO STIMULATE ALDOSTERONE AND CORTICOSTERONE SECRETION IN RATS

The effect of dopamine-antagonists on steroid secretion has revealed conflicting results regarding the confirmation of in vivo findings in vitro. In order to discriminate in vivo systemic and local action of the dopamine-antagonist haloperidol (HAL) on aldosterone and corticosterone secretion, microdialysis of the adrenal cortex in conscious, freely moving rats was employed. The effects of 2.5 mg HAL ip or intraadrenal dialysis of 20-mu-g/ml HAL in rats with an intact pituitary gland on PRL, aldosterone, and corticosterone secretion were examined. Systemic HAL application resulted in a 40-fold increase in PRL secretion and stimulated aldosterone and corticosterone production significantly. In contrast, intraadrenal dialysis of HAL had no effect on the secretory pattern of PRL or either steroid hormone, indicating no direct drug action on cells of the rat adrenal cortex. Similarly, ip injection of 2.5 mg HAL in hypophysectomized rats did not alter PRL or steroid hormone levels. We conclude that the dopamine-antagonist HAL stimulates aldosterone and corticosterone secretion in rats through a pituitary factor, probably PRL, but not through direct effects at the adrenal cortex.