Early postnatal lesions of the substantia nigra produce massive shrinkage of the rat striatum, disruption of patch neuron distribution, but no loss of patch neurons.

Abstract

Unilateral lesions of the substantia nigra in the first postnatal week cause a massive shrinkage (> 50%) of the ipsilateral rat striatum, due primarily to neuronal cell death. Striatal patch neurons (marked by retrograde labeling from the substantia nigra prior to the lesions) selectively survive the striatal cell death caused by the lesions. However, after the lesions these early retrogradely labeled patch neurons are distributed diffusely through the remaining striatum, in contrast to their normal patchy distribution throughout the postnatal period. Thus, many striatal neurons (but not the patch and matrix neurons with early axonal projections to the substantia nigra) are critically dependent upon interactions with the substantia nigra for their survival during the early postnatal period, and in the absence of these missing striatal and substantia nigra neurons, the remaining striatal patch neurons are no longer distributed in a patchy fashion.