Effects of D1‐like dopamine receptor stimulation and antagonism on cocaine choice in socially housed monkeys

Evidence supports the involvement of D2‐like and, to a lesser extent, D1‐like dopamine receptors (D2R, D1R) in the abuse‐related effects of cocaine. Effects of D2R‐acting drugs can be modulated by environmental factors including position in the social dominance hierarchy; less evidence exists for modulation of D1R‐mediated effects by social rank. Here we examined effects of acute i.v. administration of the high‐efficacy D1R agonist SKF81297 (0.1–1.0 mg/kg) and the D1R antagonist SCH23390 (0.003–0.056 mg/kg) on cocaine choice in dominant and subordinate monkeys. We used a procedure in which a complete cocaine dose‐effect curve was determined daily by making ascending cocaine doses (0.0, 0.003, 0.01, 0.03, 0.1 mg/kg/inj) available as the alternative to a food pellet under a concurrent fixed‐ratio schedule. In some subordinate monkeys, SCH23390 increased choice of lower cocaine doses. In most monkeys, however, there was no effect of either the agonist or antagonist up to a dose that decreased responding in the early components of the session. When a longer pretreatment time was used, rate‐decreasing effects were absent, and choice was no different than following saline administration. Taken together, these data suggest a lack of involvement of D1R in the relative reinforcing strength of coacine in a food‐drug choice procedure, which contrasts with previous studies using D2R agonists and antagonists. DA10584.