Membrane-associated adenosine triphosphatase in normal and injured hypoglossal nuclei.

The hypoglossal nuclei of adult male albino rats, either normal, or from 1 to 70 days after left hypoglossal nerve transection, were studied cytochemically with a lead method for sodium- and potassium-activated membrane ATP-ase, using light and electron microscopy. Reaction product was measured at the light microscopical level by microdensitometry, and significance determined statistically. Light microscopy revealed a brown reaction product in the neuropil, but none in cell bodies. Blood vessel walls were more strongly coloured. Reaction product was undiminished by ouabain pre-incubation, or by incubation without sodium or potassium, or by incubation with calcium instead of magnesium. Reaction product was diminished by absence of magnesium if calcium was also absent, and abolished if sections were boiled before incubation, or if substrate was absent. Axotomy caused a statistically significant increase in neuropil reaction product in injured nuclei, maximal at 35 days postoperatively, and subsequently decreasing to normal at 70 days. Electron microscopy showed a predominantly surface membrane reaction product, with occasional positive intracellular cisternae. Basal lamina and intra-endothelial vacuoles were also positive. Axotomy resulted in the arrival and disappearance of microglis (2 to 35 days), followed by astrocyte hypertrophy (35 days), and increase in thickness and homogeneity of surface membrane reaction product. The results suggest the presence of one or more calcium- or magnesium-dependent membrane ATP-ases. The peak of the increase after axotomy is probably partly attributable to hypertrophic astrocytes, and partly to the surfaces of neuronal processes. Increase of membrane movements might explain such enzyme activity.