Valium-like drugs use the same potentially addictive "reward pathways" in the brain as heroin and cannabis, scientists said on Wednesday, findings which may help in the search for non-addictive alternative anxiety drugs.

Researchers from Switzerland and the United States found that so-called benzodiazepine drugs, such as Ativan, Xanax and Valium, exert a calming effect by boosting action of a neurotransmitter called gamma-aminobutyric acid (GABA) in the same way as addictive drugs like opioids and cannabinoids.

This in turn activates the gratification hormone, dopamine, in the brain, the scientists said, showing that the same brain "reward pathways" are used by both types of drugs.

The findings may help in developing a next generation of non-addictive benzodiazepines, they wrote in the journal Nature.

Roche's drug Valium, known generically as diazepam, is the best known of the benzodiazepine class of drugs, which have dominated the anxiety medicine market since the 1960s.It and Ativan were among a host of other prescription drugs found in the blood of American pop star Michael Jackson when he died in June last year.

The study found that benzodiazepines seemed to work by binding to a particular part of the GABA, which the researchers named as the alpha1 sub-unit of the GABA type A receptor.

The findings show that developing similar benzodiazepines that bind to a different part may offer the same drug benefits without the addictive side effects, they said.

A study published earlier this month found that people with higher levels of dopamine in the brain tend to be more prone to addictive behavior.

Drug companies have been trying for some time to develop next-generation benzodiazepines by tweaking their chemical make-up to deliver a more selective effect that avoids unwanted side effects, but it has so far proved an uphill struggle.

German scientists conducting early research into a new compound said last year they thought they may have found a better anxiety drug which could counteract panic attacks without the side effects of existing drugs.

In 2003 Merck & Co abandoned work on another potential anxiety drug known as GABA Alpha 2/Alpha 3, after mid-stage clinical trial results were disappointing.