The effect of obidoxime on reversal or prevention of paraoxon-induced changes in the function of Chicken biventer cervices nerve-muscle preparation

Paralysis of skeletal muscles, which can lead to paralysis of respiratory muscles and death, is one of the most toxic effects of organophosphates (OPs), and oximes are the only available antidotes that can reverse or prevent such toxic effects. In the present study, the possible reversal or preventive effect of different concentrations of obidoxime (toxogonin) on changes induced by paraoxon (as an OP) on the function of skeletal muscle were investigated in chicken biventer cervices nerve-muscle (CBC) preparation using twitch tension recording technique. For this purpose, twitches of the CBC muscle 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 were recorded isotonically using Narco Biosystems. From prior studies, it was obtained that paraoxon at 10 nM induces a significant increase (more than 100%) in the twitch amplitude, and therefore, this concentration was used to examine the possible capability of obidoxime to reverse or prevent such effects. Obidoxime at 300 µM could almost fully reverse (when used as post treatment) or prevent (when used as pretreatment or at the same time as toxin) the effect of paraoxon. However, oxime at 100, 30 and 10 µM could only reverse or reduce this effect to about 25, 50 and 75% respectively. Oxime alone had also no significant on the function of the muscle at concentrations used. These data suggest that obidoxime alone may fully reverse the effect of paraoxon on skeletal muscle tissues.