Spontaneous and drug-induced locomotor activity after partial dopamine denervation of the ventral striatum.

Spontaneous and drug-induced locomotor behavior was investigated in rats subjected to lesions of the ventral striatum, using the neurotoxin 6-hydroxydopamine to produce selective depletions of dopamine. Locomotor activity changed with time after lesion. At 2 weeks postoperative less spontaneous rearings were observed compared to controls, a reduced response to 1.0 mg/kg amphetamine and an increased response to 0.1 mg/kg apomorphine. These changes were not observed 9 weeks postoperative; that is, spontaneous locomotor activity and the response to amphetamine were not different from those of controls, and the rearing response to apomorphine was now reduced. The neurochemical assays of the lesioned ventral striate showed equivalent dopamine depletions of about 48% in both lesion groups relative to controls.