A study of glial cell proliferation in the molecular layer of the dentate gyrus of the rat following interruption of the ventral hippocampal commissure.

The proliferation of glial cells in the molecular layer of the dentate gyrus in response to lesions of the ventral hippocampal commissure, has been studied autoradiographically following intraventricular injections of 3H-thymidine. Within 24 h of commissurotomy there is an appreciable increase in the number of labeled cells throughout the molecular layer which reaches its peak at approximately 36 h. This generalized glial hyperplasia persists for at least 5--6 weeks and there does not appear to be a secondary re-distribution of the newly-generated glial cells as has been reported after entorhinal lesions (Gall et al., 1979). In semi-thin plastic sections most of the proliferating cells more closely resemble the "medium-shade oligodendrocytes" of Ling et al. (1973) than typical microglia; the reactive astrocytes do not appear to participate in the glial proliferation.