title: Pregnancy alters the density of opioid binding sites in the supraoptic nucleus and posterior pituitary gland of rats.
abstract: 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.
authors.affiliation: Department of Physiology, University Medical School, Edinburgh, UK.
authors.forename: B E
authors.initials: BE
authors.lastname: Sumner
authors.forename: A J
authors.initials: AJ
authors.lastname: Douglas
authors.forename: J A
authors.initials: JA
authors.lastname: Russell
mesh_terms: 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*
chemical_list: D000700:Analgesics; D001575:Benzomorphans; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D005048:Etorphine; C027248:bremazocine