EFFECT OF PHENAGLYCODOL AND MEPROBAMATE ON SPONTANEOUS BRAIN ACTIVITY, EVOKED EEG AROUSAL AND RECRUITMENT IN THE CAT

¹ Department of Anatomy, School of Medicine, University of California at Los Angeles, Los Angeles, California

Unanesthetized, immobilized cats were used to study the effect of meprobamate and phenaglycodol on spontaneous and evoked cortical and subcortical activity in 2 types of preparations: normal intact animals, and animals with an electrolytic lesion in the rostral midbrain reticular formation sparing the lemniscal pathways and the pyramids. The drugs were administered intravenously in doses ranging from 10 to 120 mg/kg for meprobamate and 10 to 90 mg/kg for phenaglycodol. The following results were obtained.

1. High doses of both drugs (80 mg/kg and higher), reported to induce behavioral drowsiness and sleep, caused a central effect very much like that of barbiturates. They depressed the brain stem reticular formation and the thalamic recruiting system.

2. At lower doses, which appear to correlate with "tranquilizing activity," both drugs showed both stimulant and depressant effects on the brain stem reticular formation. In intact animals the stimulating effect appeared to predominate slightly.

3. Nonhypnotic doses of meprobamate (20 to 40 mg/kg, i.v.) depressed the thalamic recruiting system indirectly, presumably by increasing brain stem reticular activity, whereas phenaglycodol (10 to 20 mg/kg, i.v.) enhanced recruitment, probably by a direct effect.

4. The central mode of action of both drugs at nonsedative doses appeared to be in sharp contrast to that of barbiturates. Their mild stimulating effect on the brain stem reticular formation also differed from that of amphetamine both quantitatively and qualitatively. The central effect of meprobamate looked much like that of mephenesin, whereas phenaglycodol was shown to have certain features in common with chlorpromazine. However, it remains uncertain whether these latter similar central effects are necessarily due to similar central mechanisms of action.

Physiological and behavioral implications are discussed.