Electrophysiological studies on the effect of ethyl alcohol on central nervous system and peripheral nervous system activity

The effect of ethyl alcohol on central and peripheral nervous system activity was investigated electrophysiologically in the rabbit and the following observed. The threshold of the arousal reaction due to stimulation of the brain stem reticular formation and evoked muscular discharges of the fore and hind limbs due to stimulation of the cerebral cortex decreased with administration of a small amount of ethyl alcohol, but increased when the quantity was increased. On the other hand, the threshold of evoked muscular discharges of the fore and hind limbs due to stimulation by turns. These findings suggest that the administration of a small amount of ethyl alcohol results in activation, while that of a large quantity results in suppression of both the consciousness level and pyramidal motor activity. An inhibitory effect of ethyl alcohol on extrapyramidal motor activity is also suggested. The frequency of spontaneous unit discharges of the brain stem reticular formation increased with a small amount of ethyl alcohol, but decreased with larger quantities. This result supports the effect on arousal reaction. The amplitude of the recruiting response due to stimulation of the nucl. ventralis anterior thalami (VA) with frequency of 8Hz decreased following administration of ethyl alcohol. In the experiment on eyelid microviblation, the amplitude of photo-evoked eyelid microviblation (MV) decreased with a small amount, but increased with a large quantity of ethyl alcohol. On the other hand, the amplitude of sciatic evoked eyelid microviblation (SMV) decreased following administration of ethyl alcohol, which suggests that ethyl alcohol has an effect of suppressing pain sensation. Regarding reflex activity, ethyl alcohol increased the amplitude of M wave, H wave and the nociceptive reflex induced by stimulation of the sciatic nerve in that order. Regarding autonomic nerve activity, ethyl alcohol had almost no effect on the blood flow volume in the common carotid artery, whereas that in the femoral artery tended to decrease with the administration of a small amount of ethyl alcohol. Intestinal movement was facilitated by the administration of ethyl alcohol, but it was markedly inhibited by a large quantity of 1600mg/kg. According to EEG topography with a minicomputer system, the administration of a small amount of ethyl alcohol resulted in an increase of fast waves, while that of a large quantity resulted in an increased delta bands. These findings suggest that the administration of a small amount of ethyl alcohol results in activation, while that of a large quantity results in inhibition of central nervous system activity.