DIFFERENTIAL ACTION OF ANESTHETICS AND INTERNEURON DEPRESSANTS UPON EEG AROUSAL AND RECRUITMENT RESPONSES

¹ School of Medicine, University of California at Los Angeles and the Veterans Administration Hospital, Long Beach, California

A preparation is suggested for the study of compounds which may alter states of sleep or wakefulness. Simultaneous evaluation is made of responses to stimulation of the diffuse thalamic projection system, reticular activating system and of direct and extralemniscal sensory pathways.

Three types of anesthetic agents were found to depress the reticular activating system. Barbiturates blocked arousal at very low doses, but enhanced the recruiting response. Chloralosane in low doses enhanced recruiting, at higher doses depressed it; arousal was blocked by anesthetic doses. Ether markedly depressed responses to stimulation of either system.

The interneuron depressant agents, mephenesin, 6-methyl-2-aminobenzothiazole and 4-chloro-2-aminobenzothiazole, depressed the recruiting response, but left EEG arousal from stimulation of the reticular formation unimpaired.

It is suggested that the pathway for cortical arousal from the reticular activating system need not utilize the diffuse thalamic projection and may not depend upon interneuronal connections.

The data are considered to supply evidence that certain features of the anesthetic state may depend upon selective depression of the ascending reticular activating system.