Multiple opiate receptor subtypes are involved in the stimulation of growth hormone release by beta-endorphin in female rats.
The growth hormone (GH) secretory response to beta-endorphin and the involvement of opiate receptor subtypes in this response were determined in diestrous female rats. The involvement of the mu (mu), delta (delta) and/or kappa (kappa) site was determined by administering specific antagonists for each of these sites prior to beta-endorphin. beta-Funaltrexamine (1 or 5 micrograms) was administered to block mu sites, ICI 154,129 (5 or 25 micrograms) blocked delta sites and nor-binaltorphimine (8 micrograms) blocked kappa sites. The ability of these antagonists to block GH secretion following intravenous morphine administration was also determined. The opiate antagonists and beta-endorphin were administered into the lateral ventricle. A dose-response study for beta-endorphin indicated that 0.5 micrograms beta-endorphin was the minimum stimulatory dose for GH release, producing an approximately 4-fold increase in circulating levels of GH; lower doses of beta-endorphin did not stimulate secretion. All three antagonists were capable of blocking the stimulatory effects of beta-endorphin. These results provide evidence that all three opiate receptor subtypes are involved in the stimulatory effect of beta-endorphin on GH release.
Janik
J
J
Department of Zoology, Miami University, Oxford, Ohio.
Klosterman
S
S
Parman
R
R
Callahan
P
P
D000818:Animals; D004031:Diestrus; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D007700:Kinetics; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000502:physiology*; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors / Q000502:physiology; D017473:Receptors, Opioid, kappa / Q000037:antagonists & inhibitors / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000502:physiology; D001615:beta-Endorphin / Q000494:pharmacology*
D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C051844:norbinaltorphimine; D004743:Enkephalin, Leucine; D009271:Naltrexone; D001615:beta-Endorphin; C024524:beta-funaltrexamine; D013006:Growth Hormone; C036405:ICI 154129