Cell Counts of Purkinje and Inferior Olivary Neurons in the 'Hyperspiny Purkinje Cells' Mutant Mouse.

The mutant mouse 'hyperspiny Purkinje cells' (hpc) has morphologically abnormal Purkinje cells and below normal intracerebellar calbindin-D28k, a calcium-binding protein that, in the cerebellum, is found only in the Purkinje cells. We counted the Purkinje cells on serial sections stained with thionin or labelled with anti-calbindin-D28k antibodies to investigate whether the depletion of the cerebellar content of calbindin-D28k was correlated with a reduced number of Purkinje cells. We also counted the inferior olivary neurons, as they are one of the major afferents of the Purkinje cells and also contain calbindin-D28k. The hpc mutant mice had 27% fewer cerebellar Purkinje cells and 12% fewer inferior olivary neurons than did controls. Their Purkinje cells were evenly immunostained but slightly atrophic. These data suggest that the depleted cerebellar calbindin-D28k content could be explained both by the loss of some Purkinje cells and the reduced size of the remaining ones.