This study demonstrates potentiation by GM1 ganglioside treatment of trimethyltin (TMT) induced reactivity of astrocytes, and the expression of astroglial interleukin-1 beta (IL-1 beta) and nerve growth factor (NGF) immunoreactivities in the rat hippocampus. GM1 treatment also results in an increase of the number of IL-1 beta and NGF immunoreactive astrocytes. Both the intensity of gliosis and stimulation of IL-1 beta and NGF expression in astrocytes mostly occurs in the regions of heaviest neurodegeneration in the hippocampus (CA4/CA3c and CA1). It is tempting to assume that enhancement of astroglial NGF expression by GM1 ganglioside may play a role in the protective action of GM1 against neurotoxic insult.