The discriminative stimulus effects of cocaine in pigeons

Eight White Carneau pigeons were trained to discriminate 1.0 or 1.7 mg/kg of cocaine from saline. A fixed number of consecutive key peck responses on one key after the administration of cocaine resulted in 4-sec access to mixed grain. The same number of consecutive responses on the other key after saline also produced food. Different doses of cocaine and other drugs were tested to determine their ability to substitute (80% or more responding on the cocaine-appropriate key). The test drugs were selected to determine the selectivity of the cocaine discrimination in pigeons as well the role of different monoamines in mediating this behavioral effect. The drugs included other psychomotor stimulants, antidepressants, clonidine, yohimbine, other dopamine (1-(2-[bis(4-fluoro-phenyl)-methoxy]ethyl)4-3-phenylpropyl piperazine, GBR 12909) and serotonin (5-HT, sertraline) reuptake blockers, a D1 (SKF 75670), D2 (quinpirole), and 5-HT1A (8-hydroxy-2-(di-n-propylamino)tetralin, 8-OH-DPAT) agonist as well as the 5-HT3 antagonists, MDL 72222, LY 278584 and ondansetron. In addition, prazosin, an alpha 1 adrenergic antagonist, SCH 23390, a D1 antagonist; raclopride, a D2 antagonist and 1-(2-methoxyphenyl)-4-[4-(2-phthalimmido)butyl]piperazine (NAN-190), a putative 5-HT1A antagonist, were given in combination with cocaine to determine their ability to block the discriminative stimulus (DS) effects of cocaine, i.e., reduce drug-appropriate responding to 20% or less. The psychomotor stimulants, d-amphetamine and d-methamphetamine, completely substituted for cocaine and were similar in potency to each other and cocaine. The antidepressants I-deprenyl, imipramine, tomoxetine and bupropion also occasioned cocaine-appropriate responding.(ABSTRACT TRUNCATED AT 250 WORDS)