Reaction of the hypothalamic ventricular lining following systemic administration of MSG.

Monosodium glutamate (MSG) was used to create a lesion in the CNS of the infant rat. Subcutaneous injections of MSG in four day old rat pups caused a high degree of cell necrosis in the arcuate nucleus of the hypothalamus. The tanycytic ependyma overlying this nucleus was examined at different post injection intervals with both the SEM and the TEM. Four hours following treatment the tanycytic cell bodies appear swollen and their apical surfaces have lost most of their microvilli. Within 24 hours the affected ependymal area possesses a dense population of supraependymal cells. During the following days these alterations regress so that by the 14th day of life the ependymal surface of a treated animal is indistinguishable from that of a control animal. The changes taking place in the tanycytes are compared to those occurring in astrocytes within the body of the lesion. The morphological and ultrastructural features of the supraependymal cells are considered in their similarity to those of microglia.