Snake venom may hold key to pain relief without side effects

Nobody wants to be bitten by a black mamba. One of the most dangerous snakes in the world, its venom can kill a person in less than half an hour. But a new study reports that there is something besides deadly toxin hidden inside the snake: a powerful painkiller that works as well as morphine but without the side effects.

In the report, published Wednesday in the journal Nature, researchers from France described two previously unknown pain-killing peptides extracted from the mamba toxin. They named the peptides mambalgins, in honor of the snake.

The scientists were studying the relationship between snake venom and pain because previous research had shown that some types of venom bind directly to proteins embedded in nerve cells that cause pain when activated. These proteins, called ASICs, are commonly believed to play a central role in one of our pain pathways by causing certain groups of neurons to fire in response to a painful stimulus.

While the previous studies had focused on snake venoms that activated ASICs, the authors of the new study found that the mambalgins actually inhibit the activity of the ASICs in mice -- meaning they shut down the pathway responsible for registering pain.

The team also wanted to know if this pain-sensing pathway overlapped with the pathway stimulated by opiates. So they looked to see whether naloxone -- a drug used to combat opiate overdoses -- would reduce the effects of mambalgins. If it did, that would mean that mambalgins also utilize the same pathways as opiates, potentially leading to many of the same dangerous side-effects, such as addiction and a lowered breathing rate.

But naloxone did nothing, suggesting that the side-effects of morphine and other opiates would not be a factor with mambalgins.

The researchers also tested whether mice would develop tolerance to mambalgins. In other words, as time passes, is more of the protein needed to achieve the same pain-relieving effect, as is the case with opiates? While the mice developed some tolerance to the mambalgins, it was far less than they saw when they treated mice with opiates.

Mambalgins also did not depress the animals' respiratory rates.

While the researchers point out that much work remains to be done before mambalgins are ready to replace morphine, the preliminary results are promising. Mambalgins provide "promising new targets for therapeutic interventions against pain, and they are themselves powerful, naturally occurring, analgesic peptides of potential therapeutic value," they write.

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Snake venom may hold key to pain relief without side effects