Immunohistochemical studies on paraquat-induced damage to neuronal and glial cells in rat hippocampus

Paraquat has previously been shown to reduce the viability of rat C6 glioma cells, suggesting that this drug may be toxic to normal glial cells. Howev er, there is no direct evidence for the cytotoxic effect of paraquat on gli al cell in vivo. To investigate the toxic effect of paraquat, the damage to hippocampal neurons and astrocytes in paraquat-poisoned rat brain was immu nohistochemically examined using microtubule associate protein-2 (MAP-2) an d glial fibrillary acidic protein (GFAP) as a histological marker. Paraquat poisoning reduced the number of astrocytes in rat hippocampus in a concent ration-dependent manner. In addition, paraquat caused the damage to hippoca mpal neurons at relatively lower doses (25 and 50 mg/kg), and this neuronal damage was unexpectedly less pronounced at a higher dose (100 mg/kg). Thes e findings indicate that paraquat is toxic to astrocytes in vivo, and furth ermore suggests that the toxic effect of paraquat on glial cells may be dif ferent from that on neuronal cells in the rat brain.