Scientists in search of the control switch for the brain's dinner bell have a new clue. Researchers studying mice at Columbia University Medical Center found that when they messed with a certain protein that is found in the brains of mice - and humans - the rodents' appetite and metabolism changed.

Dr. Domenico Accili, the leader of the study, whose findings were published today in the journal Cell, said the protein seems to be intimately involved in regulating food intake, and provides an intriguing target in the never ending search for a drug to regulate how much people eat.

The protein, called Gpr17, controls how the brain's cells respond to insulin, one of the chief hormones involved in hunger and metabolism. When Accili and his team injected a drug to activate GPr17, the rodents' appetites increased; injecting a chemical to turn Gpr17 off made the mice eat less.

Accili said controlling this protein in the brains of humans may be more than just a pipe dream. Many drugs currently on the market work by acting on the family of proteins to which Gpr17 belongs. The difference is those drugs, such as asthma medicines and blood thinners, don't cross from the bloodstream into the brain.

"If we were able to tweak those medications so they cross into the brain, they could probably have positive effects against weight gain and help us control appetite," Accili said.

Accili said his team would work next on redesigning the drugs they injected into the rodents' brains so that they cross from the bloodstream into the brain.

Dr. Charles Clark, a professor of medicine at the Indiana University School of Medicine, said knowing more about this protein would no doubt help scientists learn more about appetite control in the brain and may even lead to the development of new drugs to fine-tune feelings of hunger. But overcoming hunger's deep-rooted spot in human evolution won't be so easy.

"Control of weight is too integral and too important [in human development] to have been left to the control of a single protein. The more we understand about appetite and weight control, the more complex we find them," Clark said.