Conclusions
Though the drug combinations only replicated rimcazole's effects incompletely, the present results suggest a specific decrease in the reinforcing effects of cocaine due to dual DAT σ-receptor blockade.
Methods
Male Sprague-Dawley rats were trained to lever press with food reinforcement (one or three 20-mg sucrose pellets) or cocaine injection (0.1 or 0.32 mg/kg) under fixed-ratio (FR) 5-response schedules. Drugs or vehicle were administered (i.p.) 5-min before sessions in which FR value was increased from 5 to 80. Economic demand functions were generated from effects of FR value (price) on intake (consumption), with the parameters of demand, consumption at no cost (Q0) and sensitivity to price (essential value, EV), derived.
Results
Rimcazole dose-dependently decreased Q0 and EV at both cocaine doses/injection. In contrast, rimcazole had no effect on these parameters at either food amount. Combinations of methylphenidate and the σ-receptor antagonists decreased Q0 at the lower cocaine dose/injection but had no effect on EV; these treatments were ineffective on both economic parameters at the higher cocaine dose/injection and at either food amount. Conclusions: Though the drug combinations only replicated rimcazole's effects incompletely, the present results suggest a specific decrease in the reinforcing effects of cocaine due to dual DAT σ-receptor blockade.