Enhancement of histone acetylation in midbrain of mice with ethanol physical dependence and its withdrawal

Acute and chronic consumption of alcohol (ethanol) has been reported to modify a variety of molecular events such as membrane fluidity, neurotransmitter turnover, neurotransmitter receptors, and intracellular signal transduction systems coupling to neurotransmitter receptors that alter biochemical processes in the mesolimbic dopaminergic system projecting to the nucleus accumbence and prefrontal cortex from the ventral tegmental area (Spanagel, 2009). The neurochemical process of ethanol physical dependence and withdrawal syndrome is supposed to result from adaptive changes in a number of neurotransmission systems, and several reports demonstrate the functional relationship between behavioral responses observed in ethanol-dependent and -withdrawn animals and neurotransmission systems such as glutamatergic transmission (De Witte et al., 2003; Lack et al., 2007). Ethanol alters phosphorylation of cAMP response element binding protein (CREB), and phosphorylation of CREB appears to modulate ethanol selfadministration (Yang et al., 1998). Phospho-CREB (p-CREB) level and cAMP response element (CRE)mediated gene expression are substantially changed in several brain regions in response to drugs of abuse (Nestler, 2001). Especially, changes in dopaminergic and glutamatergic inputs have been shown to induce chromatin remodelling by histone modifications (Li et al., 2004; Schroeder et al., 2008) and these events are associated with drug-related behavioral sensitization and reward (Fischer et al., 2007; Kumar et al., 2005; Li et al., 2004; McClung and Nestler, 2008; Schroeder et al., 2008). Acetylation of histone lysine residues reduces the electrostatic interaction between histone proteins and DNA, which is considered to relax chromatin structure and make DNA more accessible to transcriptional regulators (Kouzarides, 2007). It is suggested that hyperacetylation of histone H3 and H4 in promoter regions is strongly associated with gene activation (Renthal and Nestler, 2008). This association also exists in the brain in vivo in response to drugs of abuse. Moreover, intermittent binge ethanol administration also induces changes in the acetylation of histone H3 and H4 in the frontal cortex, nucleus accumbens, and striatum and effects the sensitivity of adolescent brain to ethanol via dopaminergic and glutamatergic neurotransmission (Pascual et al., 2009). However, little is known about changes in acetylation of histone H3 and H4 in the ventral tegmental area of ethanol-dependent and -withdrawn mice. In the present study, we demonstrate alterations of acetylation of histone H3 and H4, which relates to genes for neural plasticity, in the ventral tegmental area of ethanol-dependent and -withdrawal mice. Male ddY strain mice (Japan SLC, Hamamatsu, Japan) were kept in a room with an ambient temperature of 228C 6 18C and a 12 h light-dark cycle (lights on 08:00–20:00 h). Food and water were available ad libitum. All animal experiments carried out in this study were approved by the Animal Research Committee of Kawasaki Medical School and conducted according to the ‘‘Guide for Care and Use