Ethanol effects in pigeons trained to discriminate MK-801, PCP or CGS-19755.
The non-competitive N-methyl-D-aspartate (NMDA) antagonists MK-801, PCP and ketamine have recently been found to produce full drug-appropriate responding in pigeons trained to ethanol (1.5g/kg) in a two-key operant drug discrimination procedure. In the present study, ethanol (0.56-3.2g/kg i.g.) was administered to pigeons trained to discriminate MK-801 (0.18mg/kg, n = 5), PCP (1.0mg/kg, n = 4) or the competitive NMDA antagonist CGS-19755 (1.8mg/kg, n = 4) from vehicle. Up to doses that caused large reductions in response rates, ethanol produced only vehicle-appropriate responding in the pigeons trained to PCP and only low levels of drug-appropriate responding in pigeons trained to MK-801 and CGS-19755. The present results suggest there could be asymmetric generalization between the discriminative stimulus effects of i.g. ethanol and NMDA antagonists.
Departments of Pharmacology, University of Michigan, 6322 Medical Science I, Ann Arbor, MI 48109, USA.
E.R.
ER
Butelman
S.P.
SP
Baron
J.H.
JH
Woods