Anaesthetic properties of dimethylthiourea.

We have examined dimethylthiourea, a potent scavenger of free radicals, for its anaesthetic properties in mice and rats. In mice, dimethylthiourea abolished the righting reflex at intraperitoneal doses greater than 1.5 mg g-1 body-weight; in rats, it decreased the MAC value for isoflurane in a dose-dependent fashion. Dimethylthiourea 0.5 g kg-1 decreased isoflurane MAC by 23%; at a dose of 2.0-4.0 g kg-1, it abolished the response to tail clamp. Doses of 4.0 g kg-1 were lethal in the presence of isoflurane. A serum concentration of dimethylthiourea approximately 1 mg ml-1 produced a 50% reduction in isoflurane MAC. These anaesthetic properties of dimethylthiourea may influence experimental studies that examine the bio chemical and physiological properties of this agent.