title: Effects of repeated injections of naltrexone on antagonism of rate decreases by morphine in the pigeon.
abstract: Responding of three pigeons was maintained under a multiple schedule of food presentation in which key-pecks produced access to grain under a fixed-interval schedule in the presence of one stimulus and a fixed-ratio schedule in the presence of another stimulus. Repeated daily injections of 1 mg/kg naltrexone had no systematic effect on overall response rate during either schedule component, and the naltrexone continued to antagonize rate decreases of periodic single injections of 10 mg/kg morphine for seven weeks. Tolerance did not occur to the antagonistic effects of naltrexone on rate decreases generally produced by morphine.
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D010856:Columbidae; D003216:Conditioning, Operant / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors*; D009270:Naloxone / Q000031:analogs & derivatives*; D009271:Naltrexone / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D009270:Naloxone; D009271:Naltrexone; D009020:Morphine