Masashi Yanagisawa is one of those researchers who always wanted to be a scientist. His father is a practicing physician in Japan, but also studied muscle activity in the stomach. He sometimes would bring his son to the lab. "I thought it was fascinating," Yanagisawa says.

After earning an M.D. and a Ph.D., Yanagisawa wasted no time in making discoveries. The same year he secured his doctoral degree, Yanagisawa published the first research on endothelins, proteins that raise blood pressure by constricting blood vessels. Endothelins have been implicated in high blood pressure, kidney disease, and several types of cancer. Based on Yanagisawa's research, at least three drugs have been developed to block the action of endothelins and are now routinely used in the clinic.

"I'm proud of the fact that new therapies have been made from my discoveries," he says. "That doesn't happen often."

In Yanagisawa's case, it is happening more than once. Ten years after finding endothelins, Yanagisawa and others discovered a protein in the brain that seemed to jump-start hunger. The researchers named it orexin (from the Greek orexis, meaning appetite).

The next year, Yanagisawa and colleagues created mice that lacked the orexin gene. They noticed that the mice would sometimes fall asleep—suddenly, right where they stood. It looked as if the mice had narcolepsy.

The group delved further, videotaping hundreds of hours of mouse activity. But the group was discouraged that the orexin-deficient mice didn't seem all that different from normal mice. "Then we realized that mice are nocturnal!" says Yanagisawa. They started taping the mice at night—the human equivalent of daytime—and saw obvious evidence of narcolepsy.

Soon after, a Stanford group discovered that in dogs—previously the only animal model of narcolepsy—a gene that codes for an orexin receptor was linked with the disease. Clinical researchers have since found that in humans, narcolepsy is linked with orexin itself, and not its receptor: about 95 percent of people with narcolepsy do not produce orexin, Yanagisawa says.

In people with narcolepsy, the orexin-producing neurons are degenerated. Researchers now believe that narcolepsy may be a type of autoimmune disorder, in which the body mistakenly attacks these neurons and destroys them. People with narcolepsy still have fully functional receptors for orexin, however. This means that stimulating these receptors with an orexin-like molecule could potentially treat the condition. When Yanagisawa's group gave orexin to the narcoleptic mice, their narcolepsy symptoms disappeared.

His group is now working on drugs that he says could cure narcolepsy, as well as better regulate the sleep-wake cycle. "Many other people have daytime sleepiness—people on shift work, people with some types of depression, insomniacs, people with jet lag, soldiers with severe sleep deprivation. This could help any of those conditions."

Yanagisawa's discoveries may one day lead to the perfect pill. Besides its links to sleep and appetite, orexin appears to act as an energy burner: Mice given orexin can eat a high-fat diet without gaining weight.

"My dream is one pill in the morning—you're wide awake and productive, and you can eat deliciously and still lose weight!"