Left and right 6-hydroxydopamine lesions of the medial prefrontal cortex differentially alter subcortical dopamine utilization and the behavioral response to stress

The effects of left and right prefrontal cortical dopamine (DA) depletion on circling behavior, stress-escape behavior and subcortical DA function were examined in rats exhibiting left or right turning biases. 6-Hydroxydopamine lesions of the medial prefrontal cortex (PFC) caused significant DA depletions when assessed in separate studies at 3 days and 3-4 weeks. However, depletions were smaller at 3-4 weeks and there was a significant increase in DA concentration on the left side following right lesions. Significant increases in striatal DA content were observed following lesions of either side at 3-4 weeks, but not at 3 days. No changes in DA concentration were observed in the nucleus accumbens septi (NAS). Left circling rats significantly increased their circling behavior following right sided lesions and showed disrupted footshock-escape behavior following left sided lesions. Performance of the footshock-escape task exerted an effect on striatal and NAS DA utilization as indicated by the ratio of 3,4-dihydroxyphenylacetic acid (DOPAC) to DA. The effects of footshock on NAS DA utilization were greater following left PFC lesions as compared to the right lesion and sham conditions. These lesion effects were also greater in left- than in right-turning animals. The data indicate that an intrinsic asymmetry in brain DA systems interacts with left and right PFC lesions to differentially determine subcortical DA function and behaviors that it subserves.