Pregnancy alters the density of opioid binding sites in the supraoptic nucleus and posterior pituitary gland of rats.
Opioid receptor binding was measured in cryostat sections of supraoptic nucleus (SON) and posterior pituitary of virgin and pregnant rats by quantitative receptor autoradiography after in vitro incubation with [3H]etorphine or [3H](-)-bremazocine in the presence of unlabelled sub-type-selective agonists. Mu-selective [3H]etorphine-binding in the SON was reduced on the last day (21) of pregnancy vs. virgin controls (9.9 +/- 2.2 vs. 31.7 +/- 6.5 fmol/mg). Kappa-selective [3H](-)-bremazocine binding to the SON was not altered by pregnancy. Kappa-selective [3H](-)-bremazocine-binding to the posterior pituitary was less on day 16 of pregnancy vs. virgin females (19.1 +2- 5.2 vs. 74.4 +/- 16.2 fmol/mg). The results suggest mechanisms for the changes in actions of opioids on oxytocin neurones in pregnancy.
Sumner
B E
BE
Department of Physiology, University Medical School, Edinburgh, UK.
Douglas
A J
AJ
Russell
J A
JA
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001575:Benzomorphans / Q000494:pharmacology; D005048:Etorphine / Q000494:pharmacology; D005260:Female; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D013495:Supraoptic Nucleus / Q000378:metabolism*
D000700:Analgesics; D001575:Benzomorphans; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D005048:Etorphine; C027248:bremazocine