Energy Aspects of Sodium Thiopental Action on Nervous Activity

Sodium thiopental, used in a narcotic dose, makes it possible to identify the nervous processes that underlie consciousness and establish the causes of its disorder. When studying the cortical EEG activity, the impulses of individual nerve cells and the electromyographic activity of the muscles of the forelimb, it was found that thiopental blocks a number of neuronal reactions requiring energy support: tonic activating reactions to acetylcholine, applied to neurons, cease; the rate of spontaneous neuronal activity drops; the stage of non-specific activation in response to electrocutaneous stimulation disappears. So, thiopental blocks consciousness by significant limitation of the brain energy metabolism. This results in a loss of the adaptive function of the central nervous system. At the same time, glutamatergic excitation, the formation of which does not depend on energy support, is resistant to the action of thiopental. The blocking of the brain’s energy supply caused by thiopental, in accordance with its depth, develops in two stages—hypoxic and narcotic. The hypoxic stage is accompanied by hyperactivity in the nervous system, which is manifested by epileptiform discharges on the EEG and powerful unmotivated movement; the narcotic stage is associated with blockade of motor activity and flattening of EEG oscillations. The post-narcotic state associated with the consequence of the hypoxic effect of thiopental leads to the loss of ionic homeostasis and is accompanied by a steady drop in the amplitude of cortical neuron spikes.