Respiratory Enzyme Activities in Neurons and Glial Cells of the Hypoglossal Nucleus during Nerve Regeneration

Abstract

AbstractRespiratory enzyme activities were measured in the hypoglossal nucleus of the rabbit, 6, 14, 28, and 48 days after unilateral hypoglossal nerve crush in order to evaluate the changes in nerve and glial cells during axon regeneration. Succinoxidase activity was measured by the Warburg technique on homogenates of the hypoglossal nuclei and by Zeuthen's micro‐diver technique in single nerve and glial cells. Activity of succinate tetrazolium reductase, cytochrome oxidase and NADH2‐tetrazolium reductase were analyzed histochemically. Succinoxidase activity increased in single neurons up to the 14th postoperative day, both on the unoperated and operated side and was on a high level until the 28th day. A striking increase in NADH2‐tetrazolium reductase was demonstrated in the neurons on the operated side from the beginning of the second postoperative week. In the micro‐diver experiments, the glial cells of the operated side revealed a significant increase in Succinoxidase activity from the sixth to the 48th postoperative day. The histochemical study of respiratory enzymes did not reveal any change in glial enzyme activity in the hypoglossal nucleus, although morphological studies have shown hypertrophic astrocytes and reactive microglial cells in this region.The importance of analyzing nerve and glial cells separately and to consider volume and mass changes in single cells is stressed.