Increase in size of the caudate nucleus of the cat after a prenatal neocortical lesion.

In order to study the influence of prenatal developmental factors upon reaction of the brain to injury, fetal kittens (E43-48) were lesioned in the frontal or parietal cortex unilaterally and maintained into young adulthood. The animals were sacrificed by perfusion with an aldehyde fixative or by an overdose of pentobarbital. Frozen sections were cut and stained with thionin. These sections were used for calculation of caudate nuclei volumes and for measurements of neuronal and glial cell packing density and neuronal cell body size. Island and matrix compartments were sampled separately. We found that the volume of the ipsilateral caudate nucleus had significantly increased as compared to (a) the volume of the corresponding nucleus in intact cats (mean, 15%) and (b) the nucleus contralateral to the lesion (mean, 7.6%). The latter nucleus also tended to a volume increase (mean, 8.1%). The cytoarchitecture of the caudate nuclei was essentially unchanged with two exceptions. The neuronal cell packing density in the matrix compartment of the contralateral side was decreased (mean, 14.9%) while the size of neuronal cell bodies in the island compartment of the nucleus ipsilateral to the lesion was smaller (mean, 5%) relative to controls. These findings suggest that the number of neurons in the caudate of lesioned animals was larger than in intact controls, particularly on the lesioned side of the brain. This might be due to a reduction of naturally occurring cell death during development.