Note on the electric response of nerve to two stimuli

Abstract

IN a previous paper by Gerard, Hill and Zotterman(i) on the effect of frequency of stimulation on the heat-production of frog's nerve, the return of the power of liberating energy after a previous impulse was given as a function of the interval between the stimulus and its predecessor. The "total action current" also at various frequencies of stimulation was recorded with a sensitive Downing galvanometer, and it was shown that this bears a relation to the frequency of stimulation which is very similar to that shown by heat liberation.It was evident from these experiments that the power of liberating energy, as well as that of developing action potential, did not return completely to its full value in less than 50 a after stimulation. From the work of Lucas and Adrian(2) it is well known that the return of excitability in a frog's sciatic nerve is complete in about 15 a, and it has been shown that the return of the power of propagating the disturbance coincides with the return of excitability. The curve of recovery of excitability, however, was constructed by measuring the least interval for minimal muscular summation, and is therefore an expression of the return of excitability of the quickest motor fibres only of the nerve, while the experiments of Gerard, Hill and Zotterman referred to all the fibres. It was obviously desirable to confirm the results obtained on nerve stimulated at various frequencies, by observations on the total electric response to two stimuli only, with various intervals between them. This is readily done owing to the extreme sensitivity available in the high resistance Downing galvanometer employed.Method. The nerve was placed in a Lucas chamber. The stimulating electrode was placed at the spinal end, non-polarisable electrodes of the zinc-zinc-chloride-gelatin-Ringer type at the distal end; one of these was 1 Fellow of the Rockefeller Foundation.

The electric response of nerve to two stimuli

“…LXVIII. 1 THE GALVANOMETER. The galvanometer used in these experiments is similar to that previously described by Downing(2).…”

“…ZOTTERMAN (1) has recently reported that the electric response of nerve to two stimuli, when measured by the maximal deflection of a sensitive moving-magnet galvanometer, fails to reach a full doubling of the value given by the single nerve impulse until the stimulus interval is made longer than 50ar. We have continued the study of this effect, and have confirmed and extended the observations.…”

The effects of injury on mammalian nerve fibres

“…But there is really no reason to expect a greater reduction, for hitherto all experiments concerned with the point have measured the total electric effect of all the fibres in a nerve and the results have been complicated by the differences in recovery rate in different fibres (cf. Zotterman, 1928, Amberson, 1929. The present records suggest that the nerve fibre's capacity to develop the action potential returns at least as rapidly as the excitability and possibly more rapidly, and in this they agree with results obtained by Matthews ( u n p u) on single fibres nerve activated by end organ stimulation.…”