Drug discrimination history: pigeons trained to discriminate opioids with activity at different receptor types.
In pigeons (Columba livia; N = 5) trained to discriminate the mu (mu) opioid butorphanol from saline, various mu (morphine, fentanyl) but not kappa (kappa; bremazocine, U50,488, U69,593) opioids produced at least 80% drug-appropriate responding. Subsequently, pigeons were retrained to discriminate the kappa opioid bremazocine from saline; in this condition, both mu and kappa opioids produced at least 80% drug-appropriate responding, naloxone was more potent as an antagonist of the butorphanol stimulus, and chronic bremazocine treatment selectively produced tolerance to the bremazocine stimulus. Although butorphanol can function as a kappa antagonist, the effects produced by combinations of butorphanol and bremazocine during training with bremazocine were generally effect-additive. The findings indicate that the mechanisms underlying the stimulus effects of mu opioids are not altered by subsequent training with a kappa opioid. Conversely, a history of discrimination training with a mu opioid does not alter the discriminative control produced by kappa opioids during subsequent training with a kappa opioid.
Picker
M J
MJ
Department of Psychology, University of North Carolina, Chapel Hill 27599-3270, USA. mjpicker@pop.unc.edu
D000818:Animals; D001575:Benzomorphans / Q000494:pharmacology; D002077:Butorphanol / Q000494:pharmacology; D004193:Discrimination Learning / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005283:Fentanyl / Q000494:pharmacology; D006168:Guinea Pigs; D009020:Morphine / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects*
D001575:Benzomorphans; D009294:Narcotics; D011957:Receptors, Opioid; D009020:Morphine; C027248:bremazocine; D002077:Butorphanol; D005283:Fentanyl