Optic nerve changes in manganese-deficient rats.

In the present study the changes in the optic nerve due to dietary manganese (Mn) deficiency has examined in Wistar Kyoto rats, since there is a lack of information on the significance of manganese in the optic nerve. After 5 months on a Mn-deficient diet, the optic nerve was examined by light and transmission electron microscopy. The serum manganese level of the deficient rats was significantly lower than that of the controls. The light microscopic findings showed significantly fewer myelinated axons in the Mn-deficient rats and Mn-recovery rats than in the control group, and there were obviously more oligodendrocytes in the recovery rats. Ultrastructural findings were: significantly decreased diameters and lamellae of myelinated axons in the optic nerves of the Mn-deficient rats and abnormal mitochondria in the axons. Rats fed a normal diet for 3 months after 5 months on a Mn deficient diet had a normal serum manganese level, but no change in the abnormal morphology of the myelinated axons. It is concluded that the optic nerve needs manganese for the maintenance of its cell structure.