McMillan, D. E., & Li, M. (1999).
Drug discrimination under a concurrent fixed-ratio fixed-ratio schedule.
Journal of the Experimental Analysis of Behavior,
72, 187-204.
Pigeons were trained to discriminate 5.0 mg/kg pentobarbital from
saline under a two-key concurrent fixed-ratio 10 fixed-ratio 40
schedule of food presentation, in which the fixed-ratio component
with the lower response requirement was programmed to reinforce
responding on one key after drug administration
(pentobarbital-biased key) and on the other key after saline
administration (saline-biased key). After responding stabilized,
pigeons averaged 98% of their responses on the
pentobarbital-biased key during training sessions preceded by
pentobarbital, and they averaged 90% of their responses on the
saline-biased key during training sessions preceded by saline. In
test sessions preceded by doses of pentobarbital,
chlordiazepoxide, or ethanol, pigeons switched from responding on
the saline-biased key at low doses to responding on the
pentobarbital-biased key at higher doses (the dose—response
curve was quantal). High doses of phencyclidine produced
responding on both keys, whereas pigeons responded almost
exclusively on the saline-biased key after all doses of
methamphetamine. These and previous experiments using concurrent
reinforcement schedules to study drug discrimination illustrate
that the schedule of reinforcement is an important determinant of
the shape of dose—effect curves in drug-discrimination
experiments.
Key words: drug discrimination, concurrent fixed-ratio schedules,
matching law, CNS depressants, CNS stimulants, key peck, pigeons