Experimental study of the mechanism and indices of harmful effects of certain chemical substances on the central nervous system

The task of the second stage of Soviet-American cooperation on the problem of environmental health science was to explain the question of the comparative sensitivity of methods used in both countries, as well as the indices of harmful effects for the same toxic substance (carbon disulfide), with the purpose of determining the most informative methods of assessing the influence of atmospheric pollutants on organisms. The application of neurophysiological research methods (recording total electrical activity of the cortex and cortical structures of the brain, studying amplitude-time characteristics of averaged evoked potentials of the optical cortex, investigating sensory and convulsive thresholds) has made it possible to explain the neurophysiological basis of the effect of carbon disulfide on the central nervous system—the perturbation of cortical inhibition processes and the increase of excitation in amygdalate structures, both of which play an important role in the fixation process of temporary connection. The compilation of data from neurophysiological and neurochemical investigations show that neurophysiological changes are associated primarily with a decrease in enzymic breakdown of free neuraminic acid. The study of the average evoked potentials in humans during exposure to carbon disulfide concentrations of 0.09 mg/m(3) revealed a tendency to decrease the short latent amplitude components and increase the long latent amplitude components of the averaged evoked potentials. The study of operant behavior in rats revealed a characteristic change in the instrumental alimentary reactions under long-term (3 months) exposure of carbon disulfide to a concentration of 16 mg/m(3). In this manner, the following were developed in experiments with animals and research on humans: indices of the harmful effects of neurotropic toxic substances, a change in operant behavior, a decrease in the amplitude of total electrical activity, a change in time-amplitude parameters of evoked potentials, and a decrease in post-discharge convulsion thresholds in the cortical-medial nucleus of the amygdala. Neurophysiological and neurochemical research methods have proven to be the most sensitive and informative of the methods used. These criteria and methods are recommended for determining threshold levels of various neurotropic toxic substances which pollute the atmosphere.