Effects of opiate antagonists on early pregnancy and pseudopregnancy in mice.
Administration of naltrexone or the long-acting morphine antagonist chlornaltrexamine before infertile mating had no effect on the length of the resulting pseudopregnancy in mice. Naltrexone in doses of 10 to 200 mg/kg s.c. given on Days 2 or 3 of pregnancy showed no consistent effects on the maintenance of pregnancy. Multiple doses or intracerebroventricular administration of naltrexone also had no effect. Chronic infusion of naltrexone, provided by mini-osmotic pumps, from Day 1 of pregnancy had no effect on the incidence of pregnancy or the number of embryos implanted. These results suggest that endogenous opioids do not play a critical role in this prolactin-dependent physiological process.
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D005260:Female; D051379:Mice; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D011555:Pseudopregnancy / Q000187:drug effects*
D009292:Narcotic Antagonists; D001971:Bromocriptine; D009271:Naltrexone; C017120:chlornaltrexamine