Regional Differences in the Purkinje Cells Settled Pattern: A Comparative Autoradiographic Study in Control and Homozygous Weaver Mice

Abstract

To determine whether Purkinje cells located in the vermis and the lateral hemispheres of weaver mice homozygotes are distributed according to precise neurogenetic gradients, [3H]thymidine autoradiography was applied on sections of homozygous weaver mice and normal controls on postnatal day 90. The experimental animals were the offspring of pregnant dams injected with [3H]thymidine on embryonic days 11–12, 12–13, 13–14, and 14–15. The results indicate that, at the level of the vermis, neurogenetic gradients were similar for wild-type and homozygous weaver in each lobe studied of the cerebellar cortex. The same was found for the lobulus simplex and for the ansiform and paramedian lobules when the lateral hemisphere was considered. In the vermis of both experimental groups, the anterior and inferior lobes have more late-generated Purkinje cells than the central and posterior lobes, while in the lateral hemisphere, the lobulus simplex and the ansiform lobule present more early generated Purkinje cells than the paramedian lobule. In weaver homozygotes, the most important deficit of Purkinje cells, in the region of the vermis, was observed in the central lobe; depletion was less observable in the anterior lobe and least observable in the posterior and inferior lobes. In the lateral hemispheres, the most important loss of Purkinje cells was observed in the paramedian lobule, followed by the lobulus simplex. The ansiform lobule presented values that showed no statistical difference between control and homozygous weaver. When Purkinje cells were registered in the entire sections, no significant differences were observed between the two experimental groups. This was due to a considerable volume of the weaver homozygote cerebellar tissue, which has no counterpart in the control mice, compensating for the neuronal loss observed in the other studied areas of the lateral hemisphere.