At the cellular level, alcohol appears to affect brain function in a variety of ways. For example, alcohol can alter the action of the chemicals that allow neurons to communicate (i.e., neurotransmitters). Specialized proteins on the surface of neurons, known as receptors, recognize neurotransmitters and initiate the cell’s response. Neurotransmitters and receptors cluster where nerve cells come into close contact; these contacts are called synapses. Some neurotransmitters stimulate (i.e., excite) a response from the neurons that receive them; others inhibit neuronal response. Over periods of days and weeks, the levels of receptors change in response to chemical and environmental influences (e.g., drugs and synaptic activity) on the neurons. Genes in the neuron’s DNA are turned on or off, increasing or decreasing the synthesis of receptors. Over time, drugs that excite a given receptor generally lead to a reduction in (i.e., down-regulate) the numbers or activity of that receptor type. Drugs that inhibit a receptor eventually tend to lead to an increase in (i.e., up-regulate) that type of receptor. Up-and down-regulation are means by which the nervous system maintains a functional
