title: Beta-endorphin and dynorphin participate in the stress-induced release of prolactin in the rat.
abstract: In the rat, exposure to stress increases prolactin (Prl) secretion, and endogenous opioid peptides (EOP) are believed to play a role in this response. The aim of the present study was to evaluate the specific involvement of the different EOP (i.e. beta-endorphin [beta-END], dynorphin A [DYN-A], methionine-enkephalin [Met-ENK], and/or opiate receptors (i.e., mu/epsilon, kappa, delta) in the stress-related increase in circulating Prl. Rats were subjected to inescapable intermittent footshock (60 Hz, 2.5 mA, 1 s duration, 2 h) 2 h after the intracerebroventricular (i.c.v.) injection of specific antisera raised against beta-END, DYN-A or Met-ENK. In addition, selective opiate antagonists (beta h-END-[6-31], a peptide beta-END antagonist [5 nmol, i.c.v.], beta-funaltrexamine [beta-FNA], an mu 1 receptor antagonist [4.8 nmol, i.c.v.], Mr 1,452 MS and Mr 2,266 BS, two kappa-receptor antagonists [10 mg/kg body weight, i.p.], ICI 154, 129, a delta-receptor antagonist [100 nmol, i.c.v.]) were administered prior to footshock stress. Blood samples were collected through an indwelling jugular cannula. Exposure to footshock rapidly and significantly increased plasma Prl levels. This stress-induced release of Prl was reduced by both antisera against beta-END or DYN-A, as well as by pretreatment with beta h-END-(6-31), beta-FNA and kappa-receptor antagonists. Antiserum against Met-ENK and delta-antagonist were inactive. These results suggest that the activation of the two endogenous opioid systems, beta-END and DYN-A, centrally modulate the release of Prl induced by footshock stress.
mesh_terms: D000818:Animals; D004399:Dynorphins / Q000502:physiology; D004597:Electroshock; D004723:Endorphins / Q000502:physiology*; D004744:Enkephalin, Methionine / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D008297:Male; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000502:physiology*; D013312:Stress, Physiological / Q000503:physiopathology*; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins; D011388:Prolactin