Bioelectric Activity of Mammalian Nerves During X-Irradiation1

Journal/Book: Reprinted from RADIATION RESEARCH Volume 12 No. 5 May 1960 Copyright (c) by Academic Press Inc. Printed in U.S.A. RADIATION RESEARCH 12 575-586 (1960). 1960;

Abstract: Department of Biology University of Notre Dame Notre Dame Indiana 1 Supported by Research Grant AT(11-1)-205 between the U. S. Atomic Energy Commission and the University of Notre Dame. 2 Present address: Holy Names College Spokane Washington. SUMMARY The effect of X-rays an certain bioelectric responses in vitro of the ventral caudal nerves of the rat was investigated. Electronic stimulation was used to determine the amplitude of the action potential and the conduction velocity of the propagated impulse as well as the sensitivity of the nerve to stimulation. These values were determined before and during exposure to X-rays. Considerable increases in spike amplitude were noted very soon after the beginning of X-irradiation with lesser increases for sensitivity and for conduction velocity. Each factor investigated reached its maximum and declined at a time quite independent of the time at which the other factors reached their maxima. This indicated independence of controlling mechanisms. The action of X-rays was not synergistic in that the X-ray beam could be cut off and the nerve would continue to respond for some time in its enhanced condition. T he response in fact would continue to rise if it was in the rising phase when the X-ray beam was cut off and continue to fall if it was in the falling phase; the rise or fall proceeded at slower rates when the X-ray beam was cut off. The rise did not continue indefinitely but reached a certain peak after which the activity declined and ultimately fell to a level at which no response could be elicited. Stimulation at 50/sec and 100/sec caused a decline in the activity of the nerve. Once this decline was compensated for the effect of X-irradiation was evident: Stimulation at higher frequencies reduced considerably the enhancement of spike amplitude attributable to X-rays showed a somewhat lesser effect an enhancement of sensitivity and showed no effect an enhancement of conduction velocity. Nerves under stimulation and X-irradiation failed to respond as long as nerves under X-irradiation alone. RECEIVED: September 12 1959 ___MH

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