6-HYDROXYDOPAMINE LESION OF THE RAT PREFRONTAL CORTEX IMPAIRS MOTOR INITIATION BUT NOT MOTOR EXECUTION

We examined the effects of bilateral 6-hydroxydopamine (6-OHDA) lesion s of the medial prefrontal cortex (PFC) in rats on motor initiation an d execution in a simple reaction time task. Reaction times (RT) and mo vement times (MT) were measured in trained rats on four pre- and posto perative days. Animals with 6-OHDA lesions were selectively impaired o n motor initiation as measured by a significant increase in RT on each postoperative day. Motor execution was intact postoperatively, since MT was not altered. Neurochemical analysis revealed a significant depl etion of prefrontal dopamine (DA) and noradrenaline (NA) in lesioned a nimals. It was concluded that DA and, to a lesser extent, NA in the ra t PFC were involved in monitoring RT performance.