Effects on the sleeping times of male rats under amytal anaesthesia by succinate were compared with those of sodium pyruvate, solutions of both salts being introduced directly into the brain by intraventricular injection. The results were also compared with sleeping times in rats given amytal alone. Sodium succinate (1·0 M) reduced the sleeping time by about 70·0 per cent, whereas pyruvate had no effect on duration of anaesthesia. Blood levels of barbiturate were found to be unaffected by injection of succinate and, at the time of arousal, blood amytal concentration was significantly higher in succinate-treated rats than in pyruvate-treated or untreated rats. It was concluded that these results obtained in vivo corroborate previous conclusions from in vitro experiments on the intracellular site of action of the oxybarbiturates. © 1969.