Cocaine preexposure enhances sexual conditioning and increases resistance to extinction in male Japanese quail

The incentive-sensitization theory posits that drug addiction results from altered learning and motivational processes that stem from drug-induced changes in the brain's reward circuitry. Although it is generally accepted that problematic drug use results from these neuroadaptations, less research has focused on how these neural changes affect the incentive-motivational properties of naturally rewarding stimuli such as sex. The present set of experiments was conducted to investigate (1) dose-dependent effects of preexposure to chronic cocaine on sexual conditioning and (2) how prior cocaine exposure affects the extinction of sexually conditioned behavior in male Japanese quail. In Experiment 1, male quail were exposed to saline or to cocaine (5, 10, or 20 mg/kg ip) for 10 days, and their locomotor activity was measured. After a washout period, ten sexual-conditioning trials were conducted in which a light (CS) was presented prior to the presentation of a female quail (US) and approach to the light was measured. The results showed that cocaine dose-dependently enhanced sexually conditioned approach behavior and copulation. Experiment 2 was procedurally similar to Experiment 1, except that the quail received either saline or 10 mg/kg cocaine (ip) and 24 extinction trials were conducted. During extinction, no female was presented after the CS. The results showed that preexposure to cocaine delayed extinction. Therefore, cocaine may dose-dependently increase the strength of sexual conditioning, and this may subsequently increase resistance to extinction. These findings and their possible mechanisms are explored.