Effect of morphine on hypothalamic corticotropin-releasing factor (CRF) and pituitary-adrenocortical activity

The effects of intraperitoneal and intra-third ventricular administration of morphine on the hypothalamic corticotropin-releasing factor (CRF) and the pituitary-adrenocortical activity were examined in unanesthetized, freely moving rats. Hypothalamic CRF was measured by rat CRF radioimmunoassay. Intraperitoneal or intra-third ventricular administration of morphine increased blood concentrations of ACTH and corticosterone while intraperitoneal administration tended to increase CRF concentration in the whole hypothalamus including the median eminence and intra-third ventricular administration increased CRF concentration in the hypothalamus excluding the median eminence. However, morphine seemed to inhibit the increase in CRF concentration in the hypothalamus induced by the ether-laparotomy stress. The main site of morphine action on the hypothalamo-pituitary-adrenocortical system seemed to be in the hypothalamic area.