Peripheral and central administration of cocaine produce conditioned odor preferences in the infant rat

To assess the development of the reinforcing properties of cocaine, 3- to 4-day-old rat pups were administered cocaine s.c (3.0-30.0 mg/kg), intracerebroventricularly (3.0-10.0 micrograms/injection), or directly to the nucleus accumbens (1-25 micrograms/injection) in the presence of a distinctive odor. Six to 8 h later, pups were allowed a choice between the paired odor and a non-paired odor. Compared to saline treated controls, pups demonstrated a preference for the odor paired with cocaine for each route of administration. Taken together with previous work demonstrating that cocaine increases responding for electrical self-stimulation of the basal forebrain, these results suggest that cocaine is rewarding in the infant animal and that mesolimbic structures may mediate, at least in part, those reinforcing properties.