Attenuation of punishing effects of morphine and amphetamine by chronic prior treatment.

Abstract

In a previous study L. Parker et al (see record) found that the gustatory aversion normally produced by morphine did not occur when rats were first made dependent on the drug. Their explanation of this phenomenon was that dependent, withdrawn animals are in an "unnatural need state" such that a taste stimulus paired with morphine will become preferred by pairing with a beneficial need-replenishing event. This explanation was examined in the present 2 experiments with a total of 180 male Wistar rats. In Exp I the Parker et al results were supported in a conceptually similar experiment. In Exp II it was shown that analogous results could be produced with amphetamine, a drug upon which physicial dependence has not been unequivocally demonstrated and for which the regulation of self-administration does not follow the morphine pattern. Since the evidence for a "need" artificially induced by amphetamine withdrawal was not strong, the hypothesis that these data reflect preference for a substance associated with need reduction may be questioned. Of the various explanations for the phenomenon, only one involving the concept of drug tolerance has no arguments against it. (16 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)