Sydney, Sep 17 (IANS): Love to drown yourself in a peg of whiskey each evening? It may be due to impulsiveness of the brain's immune system, according to a study.

The findings showed a link between the brain's immunity and the motivation to drink alcohol at night.

This may be because our body's circadian rhythms affect the "reward" signals we receive in the brain from drug-related behaviour and the peak time for this reward typically occurs during the evening or dark phase, the researchers said.

"Alcohol is the world's most commonly consumed drug and there is a greater need than ever to understand the biological mechanisms that drive our need to drink alcohol," said lead author Jon Jacobsen, PhD student at the University of Adelaide, Australia.

"We wanted to test what the role of the brain's immune system might have on that reward and whether or not we could switch it off," Jacobsen added.

In the study, published in the journal Brain, Behaviour and Immunity, the team switched off the impulse to drink alcohol by giving mice a drug that blocks a specific response from the immune system in the brain.

The researchers administered the drug (+)-Naltrexone, which is known to block the immune receptor Toll-like receptor 4 (TLR4) in mice.

The results showed a significant reduction in alcohol drinking behaviour by mice that had been given (+)-Naltrexone, specifically at night when the reward for drug-related behaviour is usually at its greatest.

"We concluded that blocking a specific part of the brain's immune system did in fact substantially decrease the motivation of mice to drink alcohol in the evening," Jacobsen said.

These findings point to the need for further research to understand the implications for drinking behaviour in humans, the researchers noted.