Enhancement of Activity of Nerves by X-rays

Bachofer, C. S.

doi:10.1126/science.125.3258.1140

Cited by 20 publications

(5 citation statements)

References 2 publications

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“…When twenty nerves were administered x rays, there was no immediate increase in the MAP amplitude at the onset of irradiation, as was reportedelsewhere (17,18,19). It was our finding that MAP amplitudes remained unchanged, even when nerves were exposed to 100 kR (95 krad) of x rays.…”

Section: Resultssupporting

confidence: 68%

“…It has been asserted that the action potential amplitude and conduction velocity of rat caudal nerves were regularly increased or enhanced with the onset of irradiation (17,18,19). Allen and Nicholls (20) repeated these experiments on rat caudal nerve preparations and rat phrenic nerves and could find no radiation enhancement of neural activity.…”

Section: Acknowledgementmentioning

confidence: 99%

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Relation between RBE and LET to Inhibit Neural Impulse Conduction

Gaffey¹

1971

Radiation Research

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A dose of 285 krad (average) of .200-kV x rays absorbed by isolated, frog sciatic nerves promptly inactivated impulse transmission. Blockage of neural activity in this type of nerve required 600 krad (average) of 47.5-NeV protons. Protons of this energy have a relative biological effectiveness (RBE) of 0.48 with respect to 200-kV x-rays, which have an assigned value of one. Other investigators exposed frog nerves to different types of radiation and reported inactivation doses. RBE values determined, from such doses were 0.66 for 910-NeV a-particles, 0.87 for 260-kV x rays, and 30.60 for 5.3-MeV a-particles. The RBE values to suppress neural activity depended on the linear energy transfer (LET) of the radiation particles. Radiations with high LET values had high RBE values. A plot of the logarithm of RBE versus the logarithm of LET yielded a linear relation for radiations with LET values between 1.3 and 110.0 keV/i of tissue. Frog sciatic nerves exposed to either 200-kV x rays or 47.5-MeV protons exhibited bioelectric changes prior to loss of excitability. Conduction velocity decreased and the detection period (stimulus-response interval) increased after nerves absorbed only one-fourth the inactivation dose. The present investigation failed to confirm the observation of others that the action potential amplitude increased with the onset of radiation. The action potential remained unaltered even after nerves absorbed one-fourth the inactivation dose of x rays and one-half the inactivation dose of protons.

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Section: Resultssupporting

confidence: 68%

Section: Acknowledgementmentioning

confidence: 99%

Relation between RBE and LET to Inhibit Neural Impulse Conduction

Gaffey¹

1971

Radiation Research

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“…It was maintained (3)(4)(5)(6) that the MAP amplitude was enhanced or augmented with the onset of irradiation and that simultaneously there was decline in the threshold to electric stimulation. The view that irradiation provoked an immediate increase in the MAP was supported by some information (3)(4)(5)(6)10,12);…”

Section: A Maximal Action Potentialsmentioning

confidence: 99%

“…that irradiation regularly increases or enhances the MAP amplitudes from the caudal nerve of the rat. Since this point is critical, a few comments on this issue are in order.The caudal nerve preparations used by Bachofer(3,4) andBachofer and Gautereaux (5,6) contain hundreds of fibers. Bachofer and Gautereaux (6) assigned a relative value of one to the MAP amplitude at the start of irradiation.…”

mentioning

confidence: 99%

Electrophysiologic Responses of Sciatic Nerves Exposed to 200-kV X-Rays and 47.5-MeV Protons

Gaffey

1970

Advances in Biological and Medical Physics

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“…Rosen & Dawson i960). Although a depression and eventual failure of conduction has been shown by most workers (Gerstner 1956;Gasteiger & Campbell 1962), it has recently been claimed that irradiation consistently increases the amplitude of maximal action potentials in mammalian nerves (Bachofer 1957(Bachofer , 1962; Bachofer & Gautereaux 1960 a, b) reduces thresholds to electrical stimulation (Bachofer & Gautereaux 1960a; cf. Rosen & Dawson 1962) and facilitates transmission through autonomic ganglia (Bachofer 1962).…”

Section: Introductionmentioning

confidence: 98%

A study of the effect of X-rays on the electrical properties of mammalian nerve and muscle

Allen¹,

Nicholls²

1963

Proc. R. Soc. Lond. B.

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Resting potentials, action potentials, and miniature end-plate potentials have been recorded from isolated phrenic-diaphragm preparations of the rat during and after irradiation with X-rays. Relatively small doses of a few thousand roentgens have no obvious effect on the preparation for many hours but larger doses, of the order of 70 to 150 kr irreversibly block neuromuscular transmission. The block is not accompanied by any change in the size of action potentials, resting potentials, membrane constants or miniature potentials recorded in the muscle with intracellular electrodes, or in the size of action potentials recorded in the nerve. Records made at the motor end-plate show that the cause of the block is a ‘pre-synaptic ’ failure of impulse propagation in the intramuscular part of the nerve. The time course of the failure depends largely on the rate at which X-rays are delivered to the preparation: at a high dose-rate (70kr/min) the block develops rapidly and is accompanied by an increase in the frequency of miniature potentials; at a low dose-rate (7 kr/min) larger doses are required, the latency is longer and the miniature potentials continue at a normal frequency. The sequence in which different parts of the muscle become blocked, the abrupt nature of the failure at an individual motor end-plate, and the increase in frequency of the miniature potentials together suggest that the action of X-rays is to block conduction in the nerve near its terminals, possibly by depolarizing points where the axons branch and the safety factor for the propagation of impulses is low. The results reported in this paper do not support the hypotheses that small doses of X-rays at a high or a low dose-rate lead to an initial 'enhancement' of function or that they produce immediate and reversible changes in the permeability of excitable membranes to ions.

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Enhancement of Activity of Nerves by X-rays

Cited by 20 publications

References 2 publications

Relation between RBE and LET to Inhibit Neural Impulse Conduction

Relation between RBE and LET to Inhibit Neural Impulse Conduction

Electrophysiologic Responses of Sciatic Nerves Exposed to 200-kV X-Rays and 47.5-MeV Protons

A study of the effect of X-rays on the electrical properties of mammalian nerve and muscle

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