Long-term effects of neonatal ovariectomy on cerebellar development in the rat: a histological and morphometric study

The effects of neonatal ovariectomy on cerebellar development and morphology were investigated in rats ovariectomized (OV) or sham-ovariectomized (SOV) 24 h after birth. At age 70 days rats were sacrificed and the cerebella processed for quantitative light microscopy of matched midline sagittal sections of the vermis. Body, brain and cerebellar weights, as well as total cerebellar area and area of the internal granular layer were significantly greater in the OV rats. The concentration (cells/mm2) and content (cells/section) of granule cells were significantly greater in each of the 10 vermal lobules of OV rats. The number of Purkinje (P) cells in the OV rats was significantly greater than control values for 6 lobules (L-III, L-V, L-VIb,c, L-VII, L-IX and L-X). P cell number for L-I, L-II and L-VIII was also higher in the OV group, but not significantly. The between group variation for P cell packing density (cells/mm) was significantly different, i.e. packing density for the OV rats was greater than the SOV value. The most consistent and significant difference between the folial patterns of SOV and OV groups was observed in L-VIII, the pyramis. A bilobed L-VIII occurred in 61.11% of SOV rats, but only in 16.67% of OV rats. Overall, neonatal ovariectomy significantly reduced the number of folia. Although the mechanisms are speculative, these data clearly indicate removal of the ovaries 24 h after birth, either directly and/or indirectly has long-term effects on cerebellar development.