Sarin-induced neuropathology in rats.

Sarin, a highly toxic cholinesterase (ChE) inhibitor, administered at near 1 LD50 dose causes severe signs of toxic cholinergic hyperactivity in both the peripheral and central nervous systems (CNS). The present study evaluated acute and long-term neuropathology following exposure to a single LD50 dose of sarin and compared it to lesions caused by equipotent doses of soman described previously. Rats surviving 1 LD50 dose of sarin (95 micrograms/kg; IM), were sacrificed at different time intervals post exposure (4 h-90 days) and their brains were taken for histological and morphometric study. Lesions of varying degrees of severity were found in about 70% of the animals, mainly in the hippocampus, piriform cortex, and thalamus. The damage was exacerbated with time and at three months post exposure, it extended to regions which were not initially affected. Morphometric analysis revealed a significant decline in the area of CA1 and CA3 hippocampal cells as well as in the number of CA1 cells. The neuropathological findings, although generally similar to those described following 1 LD50 soman, differed in some features, unique to each compound, for example, frontal cortex damage was specific to soman poisoning. It is concluded that sarin has a potent acute and long-term central neurotoxicity, which must be considered in the design of therapeutic regimes.