Cortical Dopaminergic Involvement in Cocaine Reinforcement

TLDR

The study examined which brain sites directly reinforce cocaine use, aiming to identify neuronal systems initiating reinforcement. Rats self‑administered picomolar cocaine into specific brain regions to test reinforcement. Cocaine self‑administration was supported only in the medial prefrontal cortex, not in the nucleus accumbens or ventral tegmental area, and was reduced by the D2 antagonist sulpiride, indicating mesocortical dopaminergic receptors mediate reinforcement.

Abstract

Neuronal systems involved in the initiation of cocaine reinforcement were investigated by identifying brain sites where direct application of the drug was reinforcing. This was accomplished by allowing rats to self-administer picomolar concentrations of cocaine into discrete brain regions. The medial prefrontal cortex supported self-administration, while the nucleus accumbens and ventral tegmental area did not. Self-administration could be attenuated by including equimolar concentrations of the dopaminergic D 2 -receptor antagonist sulpiride in the microinjection system. These results imply that cocaine reinforcement is mediated in part through a direct action on mesocortical dopaminergic receptors.