ABSTRACT
Methylcobalamin is one form of cobalamin that acts as a nerve growth factor. Since adrenal medulla is part of the nervous system, therefore, this study was designed to assess the effect of methylcobalamin on this gland in rats. Albino rats were injected with methylcobalamin for 14 days; adrenals were taken, fixed in Ortho's fixative, and embedded in paraffin. They were cut in thin sections and stained with H and E and Giemsa stain. They were studied under light microscope. The result showed that methylcobalamin has stimulated the adrenal medulla, which was expressed by dilated vessels, and increase in the granularity and size of chromaffin norepinephrine containing cells. Sympathetic ganglionic cells have also increased in number and size. Cortical zona reticularis was hypervascular and hypertrophied. This study suggests that, methylcobalamin might have acted directly through the sympathetic nerves on the adrenal medulla or indirectly on the medulla through the adrenal cortex resulting in an increase in number of norepinephrine containing cells and the ganglionic sympathetic cells