Effects of Environmental and Pharmacological Manipulations on Cocaine-vs-negative Reinforcer Choice in Male and Female Rats

Rationale: The adverse consequences of human addictive drug use could be the result of either addictive drug consumption resulting in punishment (e.g., incarceration) or failure to engage in negative-reinforced behaviors that might compete with drug-maintained behaviors (e.g., contingency management strategies that reset payment amounts for drug free urines).

Objective: The goal of the present study was to establish a discrete-trial cocaine-vs-negative reinforcer (S) choice procedure where rats were presented with a simplified model of this conflict: choose negative reinforcement (i.e., escape or avoid foot shock) or choose an intravenous (IV) cocaine infusion followed by an inescapable shock.

Methods: Responding was maintained in male and female rats by IV cocaine infusions (0.32-1.8 mg/kg/inf) and a S (0.1-0.7 mA shock) under a discrete-trial concurrent "choice" schedule during daily sessions. Following parametric reinforcer magnitude and response requirement experiments, the effects of 12 h extended access cocaine self-administration and acute diazepam (0.32-10 mg/kg, IP) pretreatment were determined on cocaine-vs-S choice.

Results: Negative reinforcement was chosen over all cocaine doses. Lowering shock magnitude or increasing S response requirement failed to promote behavioral reallocation towards cocaine. Extended access cocaine self-administration sessions resulted in high daily cocaine intakes but failed to significantly increase cocaine choice in all (19) but one rat. Acute diazepam pretreatment also did not alter choice behavior up to doses that produced behavioral depression.

Conclusions: These results suggest that Ss may be a source of reinforcement that effectively compete with and mitigate maladaptive addictive drug-maintained behaviors in the general population.