Effects of ethyl alcohol on EEG and avoidance behavior of chronic electrode monkeys

¹ Merck Institute for Therapeutic Research, West Point, Pennsylvania

The electro-encephalogram (EEG) and avoidance behavior of Rhesus monkeys with chronically implanted cortical electrodes, trained on a modified Sidman avoidance schedule, were studied following acute and chronic administration of ethyl alcohol. Acute intravenous administration of alcohol in doses of 0.5–2.0 g/kg produced blood alcohol levels of 50–250 mg/100 ml. As the blood alcohol level was raised, the impairment of avoidance responding was correlated with an increase in signs of central nervous system depression as measured by EEG patterns. A dose of 2.0 g/kg of alcohol was administered intravenously once daily until signs of behavioral deficit were minimal. Initially, avoidance behavior was abolished and spontaneous EEG activity was markedly slowed during the 30-min test period. When tolerance to the behavioral effects of alcohol occurred, the EEG pattern still showed high-voltage, slow-wave activity. This study suggests that tolerance to the behavioral effects of alcohol may be acquired more rapidly than central nervous system tolerance as measured by cortical EEG activity.