Fig. 7.

Concentration-response relationships for in vitro inhibition of AChE in brain extracts from male guinea pigs at PND120–150. The AChE activity (AU/min/mg protein) measured in brain extracts pooled from four adult male guinea pigs was taken as 100% and used to normalize the AChE activity measured after in vitro exposure of the extracts to a given nerve agent concentration. The resulting concentration-response relationships were fitted to the Hill equation. Data points and error bars are mean and S.E.M. of results obtained from triplicate experiments. Although the lethal potencies of VX and sarin increased with age in male guinea pigs, their potencies to inhibit AChE activity in brain extracts from adult male guinea pigs were lower than those estimated to inhibit the enzyme activity in brain extracts from neonatal and prepubertal guinea pigs.