Morphine-conditioned changes in locomotor activity: Role of the conditioned stimulus

Rick A. Bevins, Michael T. Bardo

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


When a multisensory environment was reliably paired with morphine (2 mg/kg) in rats, that environment, in a drug-free test, evoked a hyperactive conditioned response (CR). When an olfactory cue (banana odor) was the only stimulus element reliably paired with morphine, it also elicited a hyperactive CR. However, a gustatory cue (saccharin solution) evoked a hypoactive CR. This taste-elicited decrease in activity was dose dependent; morphine at 2 and 4 mg/kg conditioned hypoactivity, whereas a higher dose (8 mg/kg) did not. A robust conditioned saccharin aversion occurred only at the highest dose of morphine, suggesting disassociation between the hypoactive CR and taste aversion. A taste cue present during context conditioning also prevented either acquisition or expression of the hyperactive CR to the context. The modality of the conditioned stimulus is a critical determinant of the form of the CR in a morphine locomotor conditioning paradigm.

Original languageEnglish
Pages (from-to)131-138
Number of pages8
JournalExperimental and Clinical Psychopharmacology
Issue number2
StatePublished - 1998

ASJC Scopus subject areas

  • Pharmacology
  • Psychiatry and Mental health
  • Pharmacology (medical)


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