23.22: Alcohol interferes with many different neurotransmitters.

So far, we’ve seen that drugs frequently can alter our brain functioning by mimicking the neurotransmitters used by our neurons during normal functioning. Their specific effects are quite predictable, as long as we know the neurotransmitter that a particular drug mimics. Their work is like a surgical strike, altering our neurochemistry in one specific way.

But what happens if the drug is more of an everyman, looking enough like many different neurotransmitters to impersonate them all? This is the case with alcohol. More specifically, it is the case with ethanol, the “alcohol” molecule in alcoholic beverages. Alcohol is a great neurotransmitter impersonator, fooling at least four different receptor molecules. Let’s look at some of its effects (FIGURE 23-51).

• 1. Alcohol slows us down, “relaxing” our neurons. By blocking receptors for glutamate (see Section 23-7), one of the brain’s chief excitatory neurotransmitters, alcohol slows our reaction times and slurs our speech. It may also have more serious effects: many animals can’t learn as well when their glutamate receptors are blocked.
• 2. Alcohol gives us a pleasant buzz. Acting like cocaine—but much weaker—alcohol blocks dopamine reuptake at synapses, increasing the concentration of this neurotransmitter that is active in the reward centers of our brain.
• 3. Alcohol blocks pain. By stimulating the release of endorphins—neurotransmitters that block pain messages—alcohol causes the same feeling that has been called “runner’s high.” Resembling morphine and heroin in this respect, but again at a greatly reduced magnitude, alcohol spurs our body to produce a little opiate-like high.
• 4. Alcohol makes us happier, at least while it’s in our system. Much like Prozac, alcohol modifies and increases the efficiency of our serotonin receptors, increasing the contentment that accompanies serotonin release at synapses in the brain. Interestingly, rats that have been bred for a high preference for alcohol turn out to have lower serotonin levels than normal rats. One possible interpretation for this is that the alcohol-seeking animals are trying to compensate for their lack of serotonin stimulation by looking for the alcohol effects.

For most people, moderate alcohol consumption is pleasant and does not have significant health risks. For some, however, alcohol abuse and alcoholism can lead to serious problems. Nearly 14 million Americans abuse alcohol, and the consequences can be serious. Beyond the effects it creates by mimicking neurotransmitters, alcohol has a variety of other physiological effects in our bodies that can become harmful when alcohol is consumed in large amounts or for long periods of time. These include increasing the risk for some types of cancer, increasing the risk of liver disease (because the liver must metabolize and detoxify all the ethanol molecules that are consumed), increasing the likelihood of harm to the fetus during pregnancy, increasing the likelihood of taking part in risky sexual and other behaviors, and increasing the risk of automobile crashes (FIGURE 23-52).