Selective cortical infarction reduces [3H]sulpiride binding in rat caudate‐putamen: Autoradiographic evidence for presynaptic D2 receptors on corticostriate terminals

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Abstract
Although the existence of presynaptic D2 dopamine receptors on corticostriate terminals has been supported by numerous receptor-bindding studies, recent autoradiographic data has failed to demonstrate loss of striatal D2 receptors following cortical lesions. In the present study, Long-Evans rats were subjected to unilateral middle cerebral artery (MCA) infarction in order to produce reproducible lesions of the neocortex without damaging subcortical structures. Animals were sacrificed 2 and 4 wk following lesion and brains were prepared for receptor autoradiography. D2 receptors were studied using the selective ligand [3H]sulpiride, while D1 dopamine receptors were examined using [3H]SCH 23390. Sodium-dependent, high-affinity choline uptake sites were labeled with [3H]hemicholinium-3, thereby providing a quantitative measure of cholinergic neuronal integrity. Unilateral cortical infarction resulted in approximately a 20% reduction in [3H]sulpiride binding in several discrete regions of the ipsilateral caudate-putamen (CPu), but not in the nucleus accumbens. D2 receptor binding was also reduced significantly in some areas of the contralateral CPu when compared with [3H]sulpiride binding in shamoperated, control animals. In contrast, D1 receptors as identified by [3H SCH 23390 and high-affinity choline uptake sites labeled with [3H]-HC-3] were not affected by the cortical lesion. The results provide autordiographic confirmation of the existence of presynaptic D2 receptors on corticostriate terminals.