Neurotoxic effect of dermally applied chlorpyrifos and cypermethrin. Reversibility of changes

Nurelle D 550 EC preparation (Dow Elanco, USA) was applied in the study. The contents of biologically active substances in 1l of the preparation was: 500 g chlorpyrifos and 50 g of cypermethrin. The experimental studies were conducted on 4 groups of rats (2 control - 10 animals in each group, and 2 experimental - 40 animals in each group). The experimental groups were dermally administered a mixture of 27.8 mg/cm(2) of chlorpyrifos and 2.7 mg/cm(2) of cypermethrin for a period of 1 week and 4 weeks (4 h daily). The control groups did not participate in the experiment. Blood was taken from the heart after 1 day, 1 week, 2 and 3 weeks after the administration of the preparation in order to determine cholinesterase activity in serum, and the brain was taken to evaluate brain cholinesterase activity. The brain for histologic studies was taken from rats 3 weeks after the experiment. The cholinesterase levels in the serum and brain initially decrease and then return to normal at 2 and 3 weeks post-exposure, respectively. Slight histopathological changes in various areas of the brain as well as increased density of the cytoplasm in neurocytes in both experimental groups were observed 3 weeks post-exposure.