The intrastriatal 6-hydroxydopamine model of hemiparkinsonism: quantitative receptor autoradiographic evidence of correlation between circling behavior and presynaptic as well as postsynatic nigrostriatal markers in the rat

Unilateral injections of 6-hydroxydopamine into the striatum resulted in almost immediate ipsilateral amphetamine (AMPH)- and delayed contralateral apomorphine (APO)-induced circling behavior in rats. APO-induced rotation correlated positively with that caused by AMPH. In these animals, there was al almost complete disappearance of dopamine uptake sites as well as increases in DA D₂ receptors in specific subdivision of the ipsilateral caudate-putamen CPu). Both the rate of AMPH- and APO-induced rotation correlated with the percentage of DA terminal loss in the total aspect and in various quadrants of the striatum. In contrast, AMPH- and APO-induced rotation correlated with the percentage increase in striatal D₂ receptors only in the dorsolateral (DL) aspect of the CPu. These results indicate that both AMPH- and APO-induced rotation can be sued to determine the extent of DA terminal loss in the rat basal ganglia. The positive correlation of circling behavior to only changes in DA D₂ receptors observed in the DL striatal subdivision provides further evidence for the heterogeneity of the basal ganglia. This model of hemiparkinsonism in the rat which uses a distant intrastriatal approach to the destruction of nigral DA cell bodies may be a more appropriate model to study the regenerative properties of the nigrostriatal DA system. This approach could also be used to more specifically localize peptidergic receptors on midbrain dopamine cell bodies