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Correlation between steady transcortical potential and evoked response

1954; Elsevier BV; Volume: 6; Linguagem: Inglês

10.1016/0013-4694(54)90021-8

1872-6380

Sidney Goldring, James L. O′Leary,

Photoreceptor and optogenetics research

In 9 cats and 3 rabbits we investigated the effects of veratrine hydrochloride, weak strychnine, 1 per cent novocaine and 1 per cent KCl upon the steady potential, evoked response, and spontaneous ECG of the somatic receiving area. Under 10−4 veratrine cyclic intense negative shifts of steady potential commence to recur immediately after its application to the cortical surface. In the negative troughs there is depression of evoked response; upon the plateaus between, the initial positive phase is markedly exaggerated and lengthened. Barbiturate spindles also change through exaggeration of their positively directed components. The SP shift which accompanies and follows barbiturate spindles of normal cortex is negative; after veratrine it becomes positive. With time spontaneous spikes of positive polarity appear upon the plateaus of veratrinized cortex, and recur after the steady potential has stabilized again. Such spikes, as well as evoked responses, acquire prolonged after-positivities with time. With 10−3 strychnine we noted exaggeration of the negatively directed components of evoked responses and of barbiturate spindles. The action of veratrine was observed to supercede that of strychnine; that is, after its application the previous effects of strychnine upon the evoked response and upon the barbiturate spindles disappeared, to be succeeded by typical veratrine effect. One per cent novocaine occasions at first an increase in amplitude and duration of the initial positive phase of the evoked response comparable with the earliest noted effect of veratrine. However, no steady potential shifts occur, and this initial effect of novocaine is followed by one of depression of the amplitude of the evoked response. After novocaine is washed off and replaced by veratrine a typical veratrine effect develops with marked exaggeration of the positive component of the evoked response. Veratrine spikes and SP negative shifts also occur. KC1 gives SP negative shifts, occasions only depression in amplitude of the evoked response. Followed by vetratrine, the effect of veratrine on the evoked response while still evident is reduced.