Wednesday, January 31, 2007

Snail Toxin and Nicotine

This post courtesy of

A New Tool Against Brain Disease

University of Utah scientists isolated an unusual nerve toxin in an ocean-dwelling snail, and say its ability to glom onto the brain's nicotine receptors may be useful for designing new drugs to treat a variety of psychiatric and brain diseases.

"We discovered a new toxin from a venomous cone snail that may enable researchers to more effectively develop medications for a wide range of nervous system disorders including Parkinson's disease, Alzheimer's disease, depression, nicotine addiction and perhaps even schizophrenia," says J. Michael McIntosh.

McIntosh is the same University of Utah researcher who as an incoming freshman student in 1979 discovered another "conotoxin" that was developed into Prialt, a drug injected into fluid surrounding the spinal cord to treat severe pain due to cancer, AIDS, injury, failed back surgery and certain nervous system disorders. Prialt was approved in late 2004 in the United States and was introduced in Europe last month.

Prialt, sold by Ireland's Elan Pharmaceuticals, took roughly 25 years to reach market after its discovery in venom from the fish-eating cone snail Conus magus or magician's cone. McIntosh says he expects it will take 10 to 20 years to develop new medications based on what is learned from the new toxin named alpha conotoxin OmIA (oh-em-one-ay) isolated from a cone snail species named Conus omaria, which lives in the Pacific and Indian oceans and eats other snails. It ranges from 1 to 3 inches long....

Diseases that Might Benefit from the New Snail Toxin

McIntosh says the OmIA toxin will be useful in designing new medicines because it fits like a key into certain lock-like "nicotinic acetylcholine receptors" found on nerve cells in the brain and the rest of the nervous system.

"Those are the same types of receptors you activate if you smoke a cigarette," he says, explaining that nicotine in cigarette smoke "binds" to the receptor to trigger the release of a neurotransmitter, which is a chemical that carries a nerve impulse from one nerve cell to another, allowing nerve cells to communicate....

A medicine that could block certain nicotinic receptors could be used to help people stop smoking cigarettes, and the same method might work for alcoholism because nicotinic receptors may be involved in alcohol addiction, McIntosh says.

Other nicotinic receptors trigger the release of neurotransmitters involved in memory, so activating the right receptors might lessen Alzheimer's memory loss.

"One reason people smoke is they feel their thinking may be a little better, with increased attention and focus," McIntosh says, noting that pharmaceutical companies "would like to mimic that positive benefit without all the downsides of cigarette smoke".

Other nicotinic receptors influence "the release of serotonin and norepinephrine, two neurotransmitters strongly implicated in mood disorders" such as depression, so a drug to activate those receptors might treat depression, he adds.

Schizophrenics tend to smoke heavily because something in cigarette smoke "seems to help them filter out irrelevant stimuli. They can focus better," McIntosh says. So a drug aimed at certain nicotinic receptors might treat schizophrenia.

New Neurotoxin is a Key for Designing New Medicines

McIntosh says the new toxin itself is unlikely to become a drug because it blocks rather than stimulates nicotinic receptors. But because it can act on some types of nicotinic receptors and not others like a key that opens some locks but not others it has great potential as a tool for precisely identifying the shape and structure of the receptor "locks," thus making it easier to design new medicines or "keys" to fit those receptors and trigger them to release desired neurotransmitters....

Posted by: Kelly Source:

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