Effect of High-Intensity X-Radiation on the A Group Fibers of the Frog's Sciatic Nerve

¹ From the Department of Radiobiology, United States Air Force School of Aviation Medicine, Randolph Air Force Base, Randolph Field, Texas

Isolated sciatic nerves of bullfrogs received x-radiation at a dose rate of 9 kr/min. Prior to and following exposure, the monophasic action potential was recorded. In alpha fibers, doses between 75 kr and 200 kr caused a decrease in conduction velocity, an increase in the rise time of the action potential, and an elevated rheobase with shortened chronaxie; the potential amplitude was not obviously affected. In the dose range above 200 kr, the potential amplitude declined rapidly and complete failure of function occurred at about 300 kr. Beta fibers closely resembled alpha fibers in behavior; however, they appeared to be somewhat more radioresistant than a portion of the alpha subdivision. Gamma fibers seemed to be most susceptible to ionizing radiation; their potential disappeared at doses between 150 kr and 200 kr.