[Activation of delta-opiate receptor simultaneously stimulates ACTH beta-endorphin and prolactin release]

To evaluate a possible physiological and pathological role of brain delta-opiate receptor and endogenous ligands in the control of ACTH, beta-endorphin (beta-EP) and prolactin (PRL) release, a specific agonist of the delta-opiate receptor--[D-Pen2, D-Pen5]-enkephalin (DPDPE) was microinjected into the third cerebral ventricle (1 microgram or 3 micrograms/3 microliters/rat) in conscious freely-moving male rats. Plasma ACTH, beta-EP and PRL concentrations were measured by radioimmunoassay (RIA). Our results clearly indicate that third ventricular injection of DPDPE significantly elevates plasma ACTH, beta-EP and PRL levels in comparison with control values, and that the stimulatory effects of DPDPE on the release of the three hormones are dose-related at 1 and 3 micrograms. The data suggest that activation of the delta-opiate receptor may be a mechanism behind the concomitant release of ACTH, beta-EP and PRL during stress and certain pathologic conditions.