Pharmacological characterization of the discriminative-stimulus effects of GBR 12909.

Squirrel monkeys were trained to discriminate the selective dopamine uptake inhibitor GBR 12909 (1-[2-[bis(4-fluorophenyl)-methoxy] ethyl]-4-(3-phenylpropyl)piperazine) from saline in a two-lever drug-discrimination procedure. After i.v. injections of GBR 12909, 10 consecutive responses on one lever produced food, whereas after i.v. saline, 10 consecutive responses on the other lever produced food. By using a cumulative-dosing procedure, several inhibitors of monoamine uptake as well as dopamine receptor agonists and antagonists were evaluated for their ability to substitute for, or attenuate, the discriminative-stimulus effects of GBR 12909. Dopamine uptake inhibitors, including GBR 12909, cocaine, 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane, mazindol, bupropion and methylphenidate, as well as the dopamine releasing drug (+)-amphetamine substituted fully (greater than 80% drug-lever responding) for the training dose of GBR 12909. In contrast, the selective norepinephrine uptake inhibitors, desipramine and talsupram, and the selective serotonin uptake inhibitor, citalopram, occasioned averages of only 13 to 19% drug-lever responding. The dopamine D1 agonist SKF 81297 (6-chloro-7,8-ddhydroxy-1-phenyl-2,3,4,5-tetrahydro-[1H]-3- benzazepine), the D2 agonists, (+)-4-propyl-9-hydroxynaphthoxazine and quinpirole, and the nonselective dopamine agonist, (-)-apomorphine, all occasioned a majority of responses (mean = 56-82%) on the drug-appropriate lever. The D1 partial agonists, R-SKF 38393 (R-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro- [1H]-3-benzazepine) and SKF 75670 (7,8-dihydroxy-3-methyl-1-phenyl-2,3,4,5- tetrahydro-[1H]-3-benzazepine), however, occasioned an average of no more than 21% drug-appropriate responding.(ABSTRACT TRUNCATED AT 250 WORDS)