Aversive conditioning in the rat: effects of a benzodiazepine and of an opioid agonist and antagonist on conditioned hypoalgesia and fear.
Hypoalgesia and fear co-occurred in rats trained on a heated floor and tested for their latencies to paw lick on that floor and to step down onto a nonheated floor. These responses were extinguished, suggesting a mediation by aversive conditioning processes. A benzodiazepine impaired the acquisition of aversive conditioning, but it did not attenuate the expression of conditioned hypoalgesia. The opioid agonist morphine also impaired acquisition across a range of drug doses and variations in hypoalgesic tolerance, whereas the opioid antagonist naloxone facilitated acquisition. The results are discussed in terms of the perceptual-defensive-recuperative (Fanselow, 1986) and working memory (Grau, 1987) models of the mechanisms for the co-occurrence of conditioned hypoalgesia and fear.
Westbrook
R F
RF
School of Psychology, University of New South Wales, Sydney, Australia.
Greeley
J D
JD
Nabke
C P
CP
Swinbourne
A L
AL
D000818:Animals; D001143:Arousal / Q000187:drug effects; D001362:Avoidance Learning / Q000187:drug effects*; D001921:Brain / Q000187:drug effects; D003214:Conditioning, Classical / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects*; D008297:Male; D008874:Midazolam / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D011963:Receptors, GABA-A / Q000187:drug effects*; D011957:Receptors, Opioid / Q000187:drug effects*; D012684:Sensory Thresholds / Q000187:drug effects; D013697:Thermosensing / Q000187:drug effects
D011963:Receptors, GABA-A; D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine; D008874:Midazolam