Chronic alcohol consumption produces alcohol tolerance and dependence.  Understanding the brain mechanisms underlying both tolerance and dependence have been challenging but involve, among many mechanisms, the differential expression of proteins in the brain that bind neurotransmitters.  For example, research from my post-doctoral fellowship in Dr. Leslie Morrow’s laboratory at the University of North Carolina demonstrated that chronic ethanol exposure alters the expression of proteins that make up GABA receptors in the brain.  These alterations are one mechanism that can lead to brain hyper excitability following cessation of alcohol consumption.  In the below data taken from Matthews et al., 1998, 40 days of chronic ethanol consumption in rats increased the expression of GABAa receptor alpha4 subunit peptide expression in the hippocampus compared to animals that did not consume alcohol.  Brain changes such as this facilitate our ability to understand the impact of chronic alcohol.