title: Effects of naltrexone on plasma corticosterone in opiate-naive rats: a central action.
abstract: We have previously reported the elevation of plasma corticosterone by i.v. naloxone HCl (NX). This work has been extended, with the current study, showing a similar effect with naltrexone HCl (NTX) and that this effect is due to a central action of the drug. Using opiate-naive male rats with chronic i.v. catheters, stereotaxically placed intracerebroventricular (ICV) cannula guides where necessary, and sound-attenuated one-way vision boxes, serial blood samples were obtained from conscious unrestrained animals. NTX (5.0, 10.0, or 20.0 mg/kg i.v.) resulted in a significant increase in plasma corticosterone 15 min following injection. I.V. administration of the methylbromide salts of each drug, which do not cross the blood-brain barrier, did not produce this same elevation in hormone level at several doses (0.4, 1.0, 2.0, 10.0 or 20.0 mg/kg). In contrast, ICV injection of either of the quaternary salts (50 micrograms/10 microliter/animal) resulted in an immediate and sustained rise in plasma corticosterone. Results obtained demonstrate that NTX has a similar effect on plasma corticosterone as NX at the appropriate doses and that the effect is a central rather than a peripheral one.
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects; D008297:Male; D009021:Morphine Dependence / Q000503:physiopathology; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology*; D010913:Pituitary-Adrenal System / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D009270:Naloxone; D009271:Naltrexone; D003345:Corticosterone