To support the free and open dissemination of research findings and information on alcoholism and alcohol-related problems. To encourage open access to peer-reviewed articles free for all to view.

For full versions of posted research articles readers are encouraged to email requests for "electronic reprints" (text file, PDF files, FAX copies) to the corresponding or lead author, who is highlighted in the posting.


Tuesday, July 26, 2011

Histone Deacetylases (HDAC)-Induced Histone Modifications in the Amygdala: A Role in Rapid Tolerance to the Anxiolytic Effects of Ethanol

Rapid tolerance to the anxiolytic effects of ethanol appears to be an important factor in the development of alcoholism. Here, we investigated the involvement of amygdaloid histone deacetylases (HDAC)-induced epigenetic changes in rapid ethanol tolerance (RET).

RET in rats was induced by 2 ethanol injections administered 24 hours apart. Both ethanol-tolerant and control rats were treated with the HDAC inhibitor, trichostatin A (TSA), and anxiety-like behaviors were measured. HDAC activity, histone (H3 and H4) acetylation, and neuropeptide Y (NPY) expression in the amygdala of these rats were also measured.

A single ethanol exposure was able to produce an anxiolytic response, inhibit amygdaloid HDAC activity, and increase both histone acetylation and NPY expression (mRNA and protein levels) in the central nucleus of amygdala (CeA) and medial nucleus of amygdala (MeA) of rats. In contrast, 2 exposures of the same dose of ethanol (24 hours apart) neither elicited a similar anxiolytic response nor modulated HDAC activity, histone acetylation, or NPY expression in the amygdala. However, exposure to a higher dose of ethanol on the second day was able to produce an anxiolytic response and also inhibit amygdaloid HDAC activity. TSA treatment caused the reversal of RET by inhibiting HDAC activity, thereby increasing histone acetylation and NPY expression in the CeA and MeA.

Cellular tolerance to the initial acute ethanol-induced inhibition of HDAC activity and the subsequent upregulation of histone acetylation and NPY expression in the amygdala may be involved in the mechanisms underlying rapid tolerance to the anxiolytic effects of ethanol.

Read Full Abstract

Request Reprint E-Mail: