Embryonic lesions of the substantia nigra prevent the patchy expression of opiate receptors, but not the segregation of patch and matrix compartment neurons, in the developing rat striatum

Unilateral lesions of the substantia nigra on embryonic day 19 prevent the development of the normal patchy distribution of opiate receptors in the ipsilateral rat striatum. Independent, early and permanent labelling of patch compartment neurons in the same brains on embryonic day 14 with [³H]thymidine revealed that the substantia nigra lesions did not prevent the aggregation of early born neurons into patches, but rather blocked the normal expression of one phenotype (dense opiate receptor binding) of these patches. Thus, early nigrostriatal connections may not be critical for the fundamental patch/matrix compartmentation of the striatum, but may be important in the maturation of phenotypic markers of these compartments.