OREXIN/ɒˈrɛksɪn/

The name given to a pair of hormones recently identified in the brains of rats by Dr Masashi Yanagisawa and his team at the Howard Hughes Medical Institute at the University of Texas. They found that these substances were generated when blood sugar levels dropped and that they acted as a trigger that caused rats to eat. When orexins were injected into rats’ brains they became ravenous and ate anything up to ten times as much food as normal. These experiments raise the possibility that it may be possible to control orexin levels by drugs and so suppress appetite in obese people or improve appetite in people suffering from post-operative stress. The name was derived by Dr Yanagisawa from the Greek orexis, “appetite”. It’s not entirely new: it had been previously applied at the end of the nineteenth century to a derivative of quinazolin which was thought for a while to be useful in increasing appetite.

Of the hormones besides orexin that are believed to be factors in appetite, one is leptin, an appetite-suppressing protein made by fat-filled adipose cells.

Philadelphia Inquirer, Feb 1998

“The highly specific expression pattern really excites people because it implies that orexins may not have a lot of other functions,” says Yanagisawa. So drugs that interfere with these proteins could have few side effects.

New Scientist, Mar 1998

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