Differential localization of pituitary-adrenal activation and temperature changes following intrahypothalamic microinjection of morphine in rats.

Microinjections of morphine (MOR) into the basal mid-hypothalamus of rats elevate corticosteroid production of adrenal glands in vitro and plasma corticosterone (B) levels. Injections in or close to the rostral part of the arcuate nucleus were most effective in producing pituitary-adrenal activation, without affecting body temperature. Injections of MOR in the anterior hypothalamic area caused hyperthermia or hypothermia, depending on the dose and the site of injection, with little or no effect on piutitary-adrenal activity. The results indicate that piutitary-adrenal activation by MOR is mediated by structures in or close to the rostral part of the arcuate nucleus and that these structures can be distinguished from structures where MOR elicits temperature changes.