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Why some people are wired to be lightweight drinkers
The mystery of how some friends end up tipsy after a single glass of wine, while others can drink pint after pint without seeming any worse for wear has finally been solved by scientists.
Scientists at Washington State University have found that, for some people, a receptor in the brain overreacts to even small amounts of alcohol, leaving them swaying, stumbling and suffering from slurred speech.
For hardcore drinkers the opposite happens, with the receptors taking far longer to be stimulated, which can lead to problem drinking and even alcoholism.
The researchers believe that increasing the sensitivity of the brain receptor – known as GABAA – can prevent people from drinking too much.
"It takes them from drinking the equivalent of three to four units of alcohol in one to two hours, down to one to two," said David Rossi, assistant professor of neuroscience at Washington State.
The mechanism responsible for alcohol sensitivity is found in the cerebellum, a part of the brain at the back of the skull which has cells with receptors connecting to the nervous system.
When activated, the GABAA receptor suppresses the firing of brain cells which is why it reduces anxiety and social inhibitions. But it also hinders other functions, such as balance and movement.
Scientists bred mice so that their receptors were sensitive to alcohol. They found that they could not stay on a rotating cylinder for very long after the equivalent of one or two drinks, in human terms.
However, mice bred to be desensitised stayed on the cylinder even after drinking three times the amount of alcohol.
"It mirrors the human situation," added Prof Rossi. "If you're sensitive to the motor-impairing effects of alcohol, you don't tend to drink much. You're inhibiting the circuit that executes normal motor function.
“If you're not sensitive, you drink more."
When the researchers injected a drug called THIP in the cerebellum of the desensitised mice it stopped the creatures from drinking too much.
The finding, said Prof Rossi, highlights a new brain region which can be manipulated to deter excessive alcohol consumption.
The research was published in the Journal of Neuroscience.