Bioelectric responses in situ of mammalian nerves exposed to X-rays

¹ Department of Biology, University of Notre Dame, Notre Dame, Indiana

X-irradiation of ventral caudal nerves of rat in vitro produces an increase in spike amplitude and in conduction velocity of the propagated impulse. In order to determine to what extent these results are due to the artificial environment in which the nerve was placed, a series of experiments was carried out in which the bioelectrical effects of x-rays on the ventral caudal nerve in situ were investigated. Immediately upon x-irradiation there was a considerable increase in spike amplitude and a somewhat lesser increase in conduction velocity. Following the increase there was a deterioration with ultimate block of conduction. At equal doses the in situ preparations were slightly more radiosensitive. There was a remarkable similarity in the responses of nerves irradiated in vitro and in situ. The effect cannot be attributed to such environmental factors as a change in temperature of the preparation or to alterations in the blood supply. The effect is apparently due to an altered condition of the nerve fiber itself, since the x-rays do not act synergistically to produce the enhancement here reported.