Age Dependent Effects of Repeated Cocaine Exposure and Withdrawal on Cortical Activity

Exposure to a drug of abuse during adolescence significantly increases the risk for addiction. However, the mechanisms underlying the increased risk remain unclear. We assessed the impact of repeated cocaine injection on cortical activity in rats, and asked whether the age at which drug exposure takes place plays a role in determining the neuroadaptations observed in the mesocortical reward system, after 3 days and 3 weeks withdrawal from cocaine. We assessed cytochrome oxidase (COI) staining as a measure of metabolic activity. In the adolescent-exposed group we found a significant COI increase in the medial prefrontal, orbitofrontal, cingulate, motor, and somatosensory cortices after 3 weeks withdrawal from cocaine injection. In the adult animals we observed a significant decrease in activity in many of the cortical structures studied. These results suggest that different forms of cortical neuroadaptation occur when cocaine is given during adolescence compared to adulthood.