The distributions of Purkinje cell perikaryon and nuclear volume in human and rat cerebellum with the nucleator method.

The Purkinje cells are among the largest cells in the central nervous system and are the output cells of the cerebellar cortex. They are, therefore, of special interest in cerebellar diseases. The estimation of total number and mean perikaryon and nuclear volume of Purkinje cells in five normal human and nine rat cerebella were obtained using unbiased methods based on stereological principles. The average total number of Purkinje cells was 30.5 x 10(6) (Coefficient of variation, CD = S.D./mean = 0.13) in humans and 0.61 x 10(6) (0.21) in rats. Thus the total number of Purkinje cells was 50 times higher in the human cerebellum compared with rats, while numerical density (number/mm3) was 13 times lower in humans (0.81 x 10(3)) compared with rats (10.1 x 10(3)). An unbiased stereological principle, the nucleator, was applied to estimate the volume of Purkinje cell perikarya and nuclei. In humans the average geometric mean volume of Purkinje cell perikaryon is 12,400 microm3 (interindividual coefficient of variation = 0.08), which is about three times larger than in rats, 4900 microm3 (CVi = 0.09). The intraindividual distributional variation (CVd) in perikaryon volume is much larger in humans compared to rats (CVd = 0.72 vs 0.32). One of the differences between the two species is the simple proportionality between perikaryon and nucleus size i humans, whereas larger Purkinje cells have relatively larger nuclei in the rat.