Olfactory cues and morphine-induced conditioned analgesia in rats

J. M. Valone, C. K. Randall, P. J. Kraemer, M. T. Bardo

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


In a Pavlovian conditioning procedure, rats were exposed to an odor conditioned stimulus (CS) and then were given morphine with its effect serving as the unconditioned stimulus (US). After four OS-US pairings, the CS was tested alone to assess the presence of an analgesic conditioned response (CR) using a hot-plate test. In Experiment 1a, two groups were conditioned by pairing either 10 mg/kg morphine or saline with an odor CS. In Experiment 1b, two groups were given an odor CS paired or unpaired with 10 mg/kg morphine. These results established that an odor cue can support a morphine-induced analgesic CR. Experiment 2 characterized tile dose-effect curve (0, 3, 10, and 30 mg/kg morphine) using an odor conditioning procedure. The dose-effect curve showed all inverted U-shaped function, with the 10 mg/kg morphine group having significantly longer paw-lick latencies compared to all other groups. This finding contrasts with the monotonically ascending dose-effect curve for the analgesic unconditioned response (UR) to morphine.

Original languageEnglish
Pages (from-to)115-118
Number of pages4
JournalPharmacology Biochemistry and Behavior
Issue number1
StatePublished - May 1998

Bibliographical note

Funding Information:
This research was supported by USPHS Grant DA07746. We thank Melinda Marion for expert technical assistance.


  • Analgesia
  • Conditioning
  • Hot plate
  • Morphine
  • Odor
  • Paw lick

ASJC Scopus subject areas

  • Biochemistry
  • Toxicology
  • Pharmacology
  • Clinical Biochemistry
  • Biological Psychiatry
  • Behavioral Neuroscience


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