Interactive effects of physostigmine and exercise on cholinesterase activity in red blood cells and tissues of rat

Physostigmine is considered to be a potential pretreatment agent against organophosphate intoxication. This investigation elicits the effects of three intensities of acute exercise (50, 80 and 100% VO2max), administration of physostigmine (70 micrograms/kg, i.m.) and the combined effect of physostigmine and three intensities of acute exercise on cholinesterase activity in red blood cells and various tissues and endurance time in rats. The cholinesterase activity in red blood cells in exercised rats not exposed to physostigmine was significantly greater than that of unexercised controls (116, 112 and 108% of control, p less than 0.05, at 50, 80 and 100% VO2max, respectively) while in other tissues the cholinesterase activity in general decreased slightly. In unexercised rats given physostigmine, the cholinesterase activity ranges were 73-79, 66-68, 68-74, 67-81 and 57-61% of controls from 10-30 min in red blood cells, brain, heart, diaphragm and thigh muscle, respectively. In exercised rats exposed to physostigmine, the cholinesterase activity ranges were 54-51, 58-50, 77-73, 71-83 and 54-58% of controls from 10-30 min in red blood cells, brain, heart, diaphragm and thigh muscle, respectively. The results indicate that in control rats not given physostigmine, different intensities of acute exercise affect the cholinesterase enzyme to a moderate degree in red blood cells (p less than 0.05) and heart (p less than 0.05) without affecting brain, diaphragm and thigh muscle. Acute exercise modifies the effect of physostigmine significantly (p less than 0.01) by increasing the cholinesterase inhibition in red blood cells and brain without affecting other tissues. Exposure of rats to physostigmine (70 micrograms/kg, i.m.) increases the endurance time in rats (160-200 g weight), possibly due to peripheral vasodilatation and lowering of core temperature.