title: Olfactory cues and morphine-induced conditioned analgesia in rats.
abstract: 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 CS-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 the dose-effect curve (0, 3, 10, and 30 mg/kg morphine) using an odor conditioning procedure. The dose-effect curve showed an 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.
authors.affiliation: Department of Psychology, University of Kentucky, Lexington 40506-0044, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Valone
authors.forename: C K
authors.initials: CK
authors.lastname: Randall
authors.forename: P J
authors.initials: PJ
authors.lastname: Kraemer
authors.forename: M T
authors.initials: MT
authors.lastname: Bardo
mesh_terms: D000698:Analgesia; D000818:Animals; D003214:Conditioning, Classical / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009020:Morphine / Q000008:administration & dosage*; D009812:Odorants; D051381:Rats; D017207:Rats, Sprague-Dawley; D012903:Smell / Q000502:physiology*
chemical_list: D009020:Morphine