Abstract
We examined the distribution of nonspecific esterase (NSE) activity in the brain of the goldfish, Carassius auritus, and found that the enzyme is expressed at high levels in cells that appeared to be radial astrocytes. Several instances in which neurons expressed NSE activity were also seen. To confirm the identity of the radial profiles as astrocytes, similar sections were labeled with antiserum against goldfish glial fibrillary acidic protein (GFAP). The concordance between the NSE and the anti-GFAP data in both the visual system and the telencephalon was essentially complete, confirming that the NSE reaction was labeling astrocytes in these structures. The two methods also gave similar results in both the cerebellum and the vagal lobes, although the concordance between them in these instances was somewhat less complete. Both the NSE reaction and immunohistochemistry with anti-GFAP serum revealed labeled nonradial cells lying free in the cerebellar molecular layer. We suggest that these cells may represent free astrocytes, a cell type that has not previously been reported in morphological studies of the teleostean brain. On the basis of our observations, we suggest that the NSE reaction may be a useful adjunct in morphological studies of teleost astroglia. Finally, we propose that the expression of NSE activity in goldfish astrocytes may he related to their ability to internalize neural debris during Wallerian degeneration.