CORTICAL INTRACELLULAR POTENTIALS AND THEIR RESPONSES TO STRYCHNINE

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Abstract
Recording with glass micropipette electrodes from the cat''s somato-sensory cortex disclosed at least 5 types of intracellular potentials, presumably from different sources. Strychnine exerted different effects on these potentials. (1) The steady potential assumed to originate in the glial elements measured 62 [plus or minus] 9 mv and remained practically unchanged after application of strychnine. (2) Spontaneous small potentials of 0.8-1.5 mv and 4-7 msec, assumed to be recorded from synaptic regions, were not recorded from the strychninized cortex. It was suggested that synchronized discharges of several of these potentials from different parts of the cell might have been one of the causes of spike discharge. (3) Spontaneous large potentials of 5-17 mv and 8-15 msec, presumably recorded from dendrites, were not found in the strychninized cortex. (4) Spike potentials, complicated by a prepotential and an inflection in the rising phase measuring 60-120 mv and 0.7-3 msec, were assumed to be recorded from nerve cell bodies. Strychnine depolarization of 20-25 mv was commonly seen, but could grow to a level of zero potential and remained there for as long as 15 msec before repolariza-tion. Depolarization of the membrane was associated with spike discharges and an increase in oscillations of membrane potential. However, if depolarization had exceeded a level of 40-50 mv, spike discharges would rapidly decrease in amplitude and finally disappear. Strychnine hyperpolarization was also observed. (5) Spontaneous simple spikes of 40-70 mv and about 0.5 msec were assumed to originate in axons. Strychnine exerted no direct effect on them.