Treatment with Nembutal (pentobarbital), a powerful barbiturate, can reduce the growth and spread of colon cancer in mice, according to findings presented Tuesday at an annual cancer meeting. Nembutal works by stimulating receptors that respond to GABA, one of the chemicals that transmit signals in nerves. But, the new findings suggest that GABA also plays a role outside of the nervous system, Dr. Premal H. Thaker, from M.D. Anderson Cancer Center in Houston, told attendees at the American Association for Cancer Research Tuesday.