Conditioned opioid release in ten-day-old rats.
Ten-day-old rats, for whom an orange scent predicted morphine injections at 5 days of age, exhibited a marked preference for orange that was fully naltrexone reversible. Moreover, such rats, when smelling orange during a heat-escape task, exhibited a higher pain threshold than control rats. Together, these findings suggest that the orange odor in conditioned rats caused a release of endogenous opioids that both sustained choice behavior and modulated pain systems.
Kehoe
P
P
Department of Psychology, Trinity College, Hartford, Connecticut 06106.
Blass
E M
EM
D000818:Animals; D001143:Arousal / Q000502:physiology*; D001245:Association Learning / Q000502:physiology*; D001921:Brain / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology*; D004723:Endorphins / Q000502:physiology*; D005260:Female; D007858:Learning / Q000502:physiology*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology; D009619:Nociceptors / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology; D011957:Receptors, Opioid / Q000502:physiology; D012903:Smell / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
D004723:Endorphins; D011957:Receptors, Opioid; D009271:Naltrexone; D009020:Morphine