How do you know when you're hungry? Or when you're full? Is it your stomach or your brain that gives you the signal?

Sure, that noisy growl or the pull on your waistband are telltale signs, but chemicals in your brain called neurotransmitters are much more reliable - and quicker to respond.

For some time, serotonin has reigned supreme as the mood-regulating neurotransmitter. Several popular diet drugs operate on the premise that by increasing the amount of time serotonin hangs around in the brain, the easier it is to keep one's appetite in check.

But serotonin has some new competition: CART peptide, or cocaine-and-amphetamine-regulated transcript.

Yes, cocaine. Researchers at Yerkes Primate Research Centre at Emory University in Atlanta discovered the CART peptide while conducting studies on this narcotic.

They found that when normal rats were injected with CART they ate 30 percent less than usual. Researchers are hopeful their discovery may eventually lead to another anti-obesity drug.

Of course, what works in rats doesn't always work in humans, particularly since humans eat for numerous reasons, many of which have little or nothing to do with hunger.

But studies such as these remind us of how eager Americans are to solve their weight problems with a pill - and how anxious pharmaceutical companies are to develop one that will do just that.

We can't help wondering what would happen if they discovered a pill that made people want to exercise.

Source: Synapse, April 29, 1998

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