SIMILARITY IN ACTION BETWEEN CURARE AND STRYCHNINE ON CORTICAL NEURONS

Abstract

[long dash][image]-Tubocurarine solution at the concn. as low as 10-7 [image], when applied topically to the cortical surface, can produce local spontaneous synchronous discharges similar to "strychnine spikes. It enhances on the one hand that component of the evoked cortical potential which is produced by the activity of intracortical neurons, and depresses on the other the afferent volleys coming from the radiation or callosal fibers. The dendritic potential produced by direct stimulation of the cortical surface is also free of the enhancing action of curare. Intraven. or intracisternal injn. of [image]-tubocurarine produces severe depression of evoked cortical potentials, but increases spontaneous cortical discharges. Intracisternal application is more effective than intraven. injn. in regard to the central stimulant action of curare. Curare as well as strychnine, despite causing spontaneous spikes, raises the threshold and lowers the magnitude of evoked cortical potentials, i.e., the general excitability of nervous tissue is depressed by the 2 alkaloids. Nevertheless, the efficiency of synchronization of the cortical neurons is improved by the alkaloids. It is suggested therefore, that both curare and strychnine possess 2 competitive actions on the central nervous system : (1) to depress the synaptic function by changing the properties of the terminal arborization of the presynaptic fibers or of the receptive membrane of the soma, and (2) to increase the cortical activity by increasing the efficiency of synchronization of nerve impulses.