Unilateral dopamine depletions attenuate the response of striatal neurons to systemic amphetamine in both hemispheres

Neuronal activity was recorded bilaterally from the striatum of intact control animals and rats pretreated 10-15 days earlier with a unilateral intranigral injection of 6-hydroxydopamine. Following isolation of single unit discharges, each group was challenged with intravenous injections of 0.2 mg kg-1 d-amphetamine administered at 2-min intervals. Striatal neurons from intact control animals responded to amphetamine with equal numbers of inhibitions and excitations. In contrast, the predominant response in the animals with lesions was no response at all even with a total cumulative dose of 2.0 mg kg-1. Approximately 50% of the neurons in each striatum of the rats with unilateral lesions failed to respond to amphetamine despite a greater than 98% difference in dopamine levels between hemispheres. The remaining neurons in these animals responded as in intact controls. These results suggest that some functional change occurs following unilateral dopamine depletion that acts to decrease the response of neurons to amphetamine in both the intact and the dopamine-depleted striatum.