The Response of Maximal and Submaximal Action Potentials from Frog Sciatic Nerve to 200-kV X-Rays

Maximal action potentials (MAP) from isolated, frog sciatic nerve were recorded before and during x-irradiation. MAP amplitudes were not changed by 10 kR of 200 kV x-rays in 19 trials; in 16 other experiments the MAP amplitudes were not altered by 100 kR of x-irradiation. Sixteen nerves were irradiated until complete suppression of the MAP was evidenced, which required 300 kR (average) of x-rays. Rapid attenuation of the MAP amplitude was initiated with 160-200 kR of x-rays. Twelve nerves exhibited a 4-10% increase of the MAP amplitude prior to rapid attenuation; four other nerves revealed only decreases in the MAP amplitude with x-rays in excess of 160 kR. In these experiments the maximal threshold stimulus (MTS) to evoke a MAP remained unchanged below 100 kR of x-rays; during attenuation of the MAP amplitude the MTS increased. The duration of the MAP increased in all nerves exposed to 20 kR of x-rays even though the MAP amplitude remained unaffected. In some cases 10 kR of x-rays provoked changes in the...