Cocaine: acute effects on reinforcement thresholds for self-stimulation behavior to the medial forebrain bundle.

Reinforcing thresholds for self-stimulation behavior to the medial forebrain bundle were determined in rats by means of rate-free psychophysical method. The acute administration of cocaine lowered the reinforcing thresholds independent of motor stimulatory effects. These results indicate that cocaine affects the sensitivity of the reward pathways in the brain, and further demonstrate the utility of rate-independent methods in the assessment of drug effects on self-stimulation behavior.