*2.5.1. Microarray study*

the total phosphorylated c-AMP response element-binding protein (CREB) immunoreactivity is reduced in both chronic or binge drinking. In rat cerebellum, the dose of 3 g/kg alcohol (acute) shows an increase in a phosphorylated form of CREB. Research showed that protein phosphatase inhibitor (DARPP-32), when it undergoes phosphorylation changes, plays a crucial role in reduc-

They are the first signaling proteins which are regulated through sensitive cysteine residues, which need to be reduced to its function. Earlier studies showed that production of reactive oxygen species (ROS) is responsible for the activation of NF*κ*B [53]. Later *in vitro* studies showed that exogenous hydrogen peroxide is responsible for NF*κ*B activation [54]. In the cortex, one study reported activation of NF*κ*B in chronically alcoholized rats [55]. It was quite clear that NF*κ*B was down-regulated in comparison to acute alcohol drinking. One study showed no NF*κ*B activation in binge alcohol drinking models, when given anti-oxidants

It is an efficient mechanism for gene regulation by altering the packaging of DNA within chromatin through interactions with histones. CREB requires phosphorylation to initiate transcription of pro-survival neuronal factors (**Figure 2**). A study revealed an increase in CREB (a regulator for plasticity of neurons), increase in H3-H4 (a central histone tetramer) acetylation and inhibition of HDAC (histone deacetylases) activity in a rat amygdala when given an acute dose of ethanol for 15 days. A trichostatin (HDAC inhibitor) was used to treat the rats, resulting in deacetylation of H3-H4, CREB inhibition, reduced NPY expression and HDAC

(furosemide and butylatedhydroxytoluene) to prevent neuronal degeneration [56].

ing ethanol inhibition of NMDA receptors [52].

*2.3.3. Transcription factors*

20 Drug Addiction

**2.4. Epigenetic mechanism**

activation in the rat amygdala [57].

**Figure 2.** Epigenetic modifications associated with alcoholism.

First genome microarray studies were performed in post-mortem alcoholics' human brain; results revealed that myelin related genes expressed in oligodendrites (from frontal cortex) showed downregulation in the brains of human alcoholics compared with brains from control individuals [58], suggesting neuronal dysfunction. In the prefrontal cortex area of the brain, there were 54 genes which were upregulated and those belong to the class of heat shock protein, including *HSP70–2, CRYAB, HSP27–1* and *HSP40–1* in alcoholic abusive individuals [59]. An old study revealed that 100 mM ethanol (2 days) given to NG108–15 hybrid cell line determined that a number of genes were induced by heat shock and a few were induced by ethanol only. Heat-shock cognate proteins *Hsc 70* and *Hsc 110* were recognized as ethanol-inducible genes [60]. When *C. elegans* was given a high dose of ethanol, it showed activation of *glr-2*, a gene that encodes a subunit of the AMPA glutamate receptor subunit (homologous to mammalian GluR2) within 15 min [61]. Cultured cortical neurons given 75 mM of ethanol for 5 days showed increased levels of gene expression of *Hsp84, Hspa8* and *Hsp70* [62]. In a whole brain, when C57BL/6J and DBA/2J mouse strains were given acute doses of different ethanol preferences, they revealed downregulation of *Erbb3*, *Mobp* and *Nkx2-2* (myelin-related genes) [63].

The researcher performed a genomic level along with a microarray experiment on neurons of mouse corticals given 60 mM ethanol or heat treatment at 42°C. Microarray results showed upregulation of a large number of genes by ethanol and heat shock [64]. Among the pool of genes, there were nine genes which showed greater than 50% stimulation. It includes.

