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) deplet ion on circling behavior, stress-escape behavior and subcortical DA fu nction 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 ther e was a significant increase in DA concentration on the left side foll owing 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 accu mbens septi (NAS). Left circling rats significantly increased their ci rcling behavior following right sided lesions and showed disrupted foo tshock-escape behavior following left sided lesions. Performance of th e footshock-escape task exerted an effect on striatal and NAS DA utili zation as indicated by the ratio of 3,4-dihydroxyphenylacetic acid (DO PAC) to DA. The effects of footshock on NAS DA utilization were greate r following left PFC lesions as compared to the right lesion and sham conditions. These lesion effects were also greater in left- than in ri ght-turning animals. The data indicate that an intrinsic asymmetry in brain DA systems interacts with left and right PFC lesions to differen tially determine subcortical DA function and behaviors that it subserv es.