D4 dopamine receptor-specific antagonist improves reversal learning impairment in amphetamine-treated male rats

The Attentional Set-Shifting Task (ASST) is a rodent analog of the Wisconsin Card Sorting Task, which measures executive functioning. The ASST tests for reversal of stimulus-response learning and the formation and maintenance of attentional sets. Depletion of dopamine has been shown to improve performance on attentional shifts. The study presented here questioned whether a D₄-specific antagonist, L-745,870, could have a similar effect on animals, even after being treated with repeated doses of amphetamine. Three groups of male rats were given either 10 saline injections (n = 12), 10 amphetamine injections (2 mg/kg; n = 8), or 10 amphetamine injections plus 1 pretreatment injection of L-745,870 (0.1 mg/kg; n = 8) 20 min prior to testing. One-way ANOVA results showed that amphetamine-only rats were impaired on all 3 reversals (Ms = 19, 16.4, and 17.1) compared with L-745,870-treated rats (Ms = 9.8, 10.9, and 9.6) and controls (Ms = 8.6, 9.6, 9.3; all ps < .01). L-745,870-treated rats also displayed reduced latencies to respond compared with both saline controls and amphetamine rats. It is thought that D₄ receptors play a role in cue salience, and that by blocking these receptors, animals display less attachment to previously rewarded cues. The results presented support this idea and imply that blocking of D₄ receptors can reverse the impairment in reversals caused by amphetamine.