The activity of AChE was elevated in the brain areas of these animals after exposure to noise stress . The F-test ratio (d.f.: 5, 30) in each area of the brain was found as follows: cerebral cortex = 12.939 (p < 0.001), corpus striatum = 41.096 (p < 0.001), hypothalamus = 17.155 (p < 0.001) and hippocampus = 8.660 (p < 0.001). However in the groups of rats pretreated with OS extract for 7 days and subjected to noise stress on 8th day, the val-