ADDICTION TO alcohol could soon be cured by a pill designed to block the pleasure pathways of the brain involved in enjoying a drink, American scientists report today.

Experiments on genetically engineered mice have led to the discovery of a protein in the brain that determines how the body responds to alcohol. Blocking the protein could help to cure alcoholism.

The mice lacked one of the protein receptors in the brain, called D2 receptors, which bind to dopamine, a chemical messenger involved in stimulating the brain's pleasure pathways.

Without the D2 dopamine receptors, the genetically engineered mice showed an aversion to alcohol and were more resistant to its effects compared with normal mice.

"Suppose you could create a drug that bound to the D2 receptor so that dopamine couldn't bind to that receptor at all," said Tamara Phillips, professor of behavioural science at Oregon Health Sciences University. "That would be like getting rid of the receptor. If you could do that, then you might be able to reduce drinking."

The D2 receptor is one of five in the brain involved with binding to dopamine, which is believed to regulate the feelings of pleasure and craving associated with addictive drugs.

David Grundy, professor of physiology and pharmacology at the university, warned, however, that the research - published in the scientific journal Nature Neuroscience - had some way to go. "It will require extensive genetic screening of humans to determine which specific mutations in the D2 receptor gene may be connected with alcoholism. Our research doesn't point towards a single alcoholic gene, but rather a complex interaction ..."