Nociceptive assessment modifies behavioral tolerance without altering brain morphine concentration.
The influence of nociceptive assessment on the development of behavioral tolerance and on brain morphine concentration was examined in morphine pellet-implanted rats. Tolerance was facilitated by experience with the nociceptive tail flick test procedure, whereas whole brain opiate levels, determined by radioimmunoassay, were not altered by the behavioral tests. Parallel experiments with placebo-implanted rats indicate the significance of environmental context in nociception. These results demonstrate that behavioral manipulations can significantly modify pharmacological effects without altering drug concentration in the brain.
D000698:Analgesia; D000818:Animals; D001921:Brain / Q000378:metabolism*; D004361:Drug Tolerance; D008297:Male; D009020:Morphine / Q000378:metabolism / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time
D009020:Morphine