Dr. Subhash C. Pandey, professor and director of neuroscience alcoholism research at the UIC College of Medicine and the Jesse Brown VA Medical Center in Chicago, says that these "epigenetic" changes are minor chemical modifications of chromatin, dense bundles of DNA and proteins called histones.

"This is the first time anyone has looked for epigenetic changes related to chromatin remodelling in the brain during alcohol addiction," said Dr. Pandey, the lead author of the study reported in the Journal of Neuroscience.

Dr. Pandey and his colleagues studied the activity of histone deacetylases (HDAC) that remove acetyl groups from histones and, thereby, cause them to wrap with DNA more tightly, decreasing gene expression.

The researchers also looked at the expression of the genes for NPY in the amygdala, and the anxiety-like behaviours associated with withdrawal from chronic alcohol use.

They found that anxiety-like behaviours during withdrawal in animals with chronic alcohol exposure was associated with an increase in HDAC activity and decrease in histones acetylation and NPY levels.

When the researchers blocked the observed increase in HDAC activity using an HDAC inhibitor during alcohol withdrawal, it brought up histone acetylation and NPY expression levels in the amygdala and, thus, prevented the development of anxiety-like behaviours.