Evaluation of the changes in contractility of Chick biventer cervices nerve-muscle encountered with Paraoxon and Pralidoxime: Introduction of a non- enzymatic method

One of the most toxic effects of organophosphate (OP) poisoning is the paralysis of skeletal muscles, which can lead to paralysis of respiratory muscles and death. However, in this regard, oximes are the only antidotes available to reverse or prevent such toxic effects of OP insecticides and nerve chemical warfare agents. In the present work, effect of different concentrations of paraoxon (as an OP) on the function of skeletal muscle and reversal of these effects by an oxime (Pralidoxime, 2-PAM) were studied in chick biventer cervices nerve-muscle preparation using twitch tension recording technique. Twitches of the biventer cervices were evoked by stimulating the motor nerve at 0.1 Hz with pulses of 0.2 msec duration and a voltage of greater than that required to produce the maximum response. Twitches and contractors were recorded isotonically using Narco Biosystems. Paraoxon (0.1 µM) induced a highly significant increase (more than 100%) in the twitch height, while higher concentrations (0.3 and 1 µM) could induce partial or total contractors. Therefore, Paraoxon at 0.1 µM was used to examine the capability of Pralidoxime to reverse its effects. Pralidoxime at 100 µM, or higher, could almost fully reverse the effect of paraoxon. While, oxime at 30 and 10 µM could only partially reverse this effect concentration-dependently. These results suggest that the method used is of high value in studying the functional effects of OPs on skeletal muscle tissues and the reversal effects of antidotes.