REDUCTION IN STRIATAL D2 DOPAMINE-RECEPTOR MESSENGER-RNA AND BINDING FOLLOWING AF64A LESIONS

Unilateral lesions by a cholinotoxin, receptor autoradiography, and in situ hybridization techniques were employed to determine if dopaminer gic receptors are located on cholinergic interneurons in the caudate-p utamen (CPu). Lesion of the CPu with small amounts of the cholinotoxin AF64A resulted in a significant decrease in D2 receptor mRNA and D2 r eceptor binding. The loss was more pronounced in lateral and central p ortions of the CPu. Results obtained using [H-3]SCH23390 binding to D1 receptors indicated that there was no change in this dopamine recepto r subtype in the AF64A-lesioned CPu. A decrease in D2 receptor mRNA an d receptor binding in AF64A-lesioned animals indicates that a populati on of postsynaptic D2 receptors is associated with the cholinergic int erneurons. Lack of any change in [H-3]SCH23390 binding in the AF64A-le sioned animals suggests that D1 receptors are not located on cholinerg ic neurons. These results provide evidence to support the selectivity of the lesion when used as indicated.