Parametric investigations of the effects of prior exposure to amphetamine and morphine on conditioned gustatory aversion.
Pretreatment by a psychoactive drug can greatly attenuate the conditioning of gustatory avoidance by that drug. Although such findings have been interpreted in terms of tolerance, alternative explanations are possible. In a series of experiments, it was found that pretreatments with morphine or amphetamine massed at 24-h intervals were no more effective in attenuating conditioning than pretreatments spaced at 120-h intervals, but pretreatment with morphine provided more persistent protection against subsequent conditioning by itself than did amphetamine in a comparable previous experiment. The similarity of massed and spaced pretreatment effects can be interpreted without appealing to tolerance as a factor, but the greater persistence of morphine pretreatment implicates tolerance as a mechanism.
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D003213:Conditioning, Psychological / Q000187:drug effects*; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D004361:Drug Tolerance; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D013649:Taste; D013997:Time Factors
D009020:Morphine; D003913:Dextroamphetamine