People who use heroin have abnormally high levels of a brain chemical serikbaib/Getty

Heroin users have been found to make abnormally high amounts of a brain chemical that promotes “wakefulness”. The finding might lead to new treatments for narcolepsy, a condition in which people fall asleep uncontrollably.

Previous research has shown that people normally have around 70,000 cells in their brain that produce a chemical called hypocretin. But in narcoleptics 90 per cent of these cells stop making this substance. Now, a team has discovered by chance that people who are addicted to heroin are capable of making very large amounts of it.

Post-mortem analysis of the brains of five heroin users revealed that each person had, on average, 54 per cent more hypocretin-producing cells than brains normally do.


The finding suggests hypocretin could be motivating an addict’s use of heroin, says Jerome Siegel of the University of California at Los Angeles, whose team made the discovery.

New treatments

Siegel says hypocretin might hold the key to treating both conditions. Heroin users make too much and narcoleptics too little, so both might benefit from treatments that restore levels to normal.

When Siegel gave morphine—which is similar to heroin—for at least two weeks to mice genetically engineered to have narcolepsy, the drug restored levels of hypocretin to normal and eased their condition.

Siegel and his colleagues are currently screening milder opiates such as codeine for suitability to treat narcolepsy. Given that many opioids are addictive, and have led to a surge in overdose deaths in the US, any possible narcolepsy treatment would ideally be based on a non-addictive drug.

Source: Science Translational Medicine, DOI: 10.1126/scitranslmed.aao4953

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