X-RAY EFFECTS ON SINGLE NERVE FIBERS*

Journal/Book: Reprinted from THE JOURNAL OF GENERAL PHYSIOLOGY March 20 1959 Vol. 42 No. 4 pp. 723-735 Printed in U.S.A.. 1959;

Abstract: From the Department of Biology University of Notre Dame Notre Dame Indiana (Received for publication September 15 1958) *Supported by Research Grant AT(11-1)-205 between the United States Atomic Energy Commission and the University of Notre Dame Present address: Holy Names College Spokane Washington. ABSTRA

Keyword(s): Electrophysiological responses of median and lateral giant nerve fibers of the earthworm were recorded during exposure in vitro to x-rays. In response to external stimulation during x-irradiation these nerve fibers showed initially an increase in conduction velocity a rise in spike amplitude a decrease in relative refractory period and an increase in sensitivity. These responses represent an enhancement of activity attributable to bombardment with x-rays rarely found in other biological Systems. They were followed by deterioration of activity and eventual Block representative of the lethal action of x-rays commonly observed in other biological systems. Several properties of the enhancement of activity were noted: The time at which maximum activity of one factor occurred did not coincide with the time at which the maxima of other activities occurred; spike amplitude for example was observed to increase while conduction velocity had already reached its maximum and was rapidly declining. The energy supplied by bombardment with x-rays did not act synergistically during the time of the enhanced response; that is concomitant irradiation was not necessary in order to produce the enhanced response once the nerve had been altered by x-irradiation. Once the nerve was responding in an enhanced manner cessation of irradiation for short periods of time had no effect an the response. The phenomenon was therefore due to an irreversible alteration of the nerve fiber itself. ___MH

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