Effects on Brain Function by Addictive Substances

Brain activity is a result of nerves firing or not firing in binary fashion. It is similar to the functioning of computers, where complicated processes are described with a series of 0’s and 1’s. After the nerves fire, neurotransmitters must be removed from the area in order to turn the signal off. Two possible ways are available for the removal of the neurotransmitters; either an enzyme destroys the chemical or it is pumped back into a nerve by using another chemical called a transport pump. The process of pumping chemicals back is known as reuptake.

Alcohol work similarly to all psychoactive compounds, like neurotransmitters, hormones, addictive drugs and medications. Alcohol and other chemicals work as a key that fit into a specific lock, and opens a door for further communication. Alcohol works on both the motor and sensory components of the brain, and has multiple neurotransmitter effects, although it does have a receptor that is specifically designed for it. This is not unique to alcohol, since opiates have opiate receptors, and marijuana has marijuana receptors, which means that the body produces chemicals with similar activity.

Certain brain areas are particularly sensitive to the effects of alcohol. The neurotransmitters affected by alcohol include gamma-amino butyric acid (GABA), glutamate, serotonin, dopamine and endogenous opiates. These neurotransmitters are involved in the alcohol’s short and long-term effects, including intoxication, withdrawal and possibly addiction.

GABA is the main inhibitory neurotransmitter of the brain, which is responsible for dampening and inhibiting brain activity. The increase of GABA leads to a decrease of motor tension and anxiety, and increases sedation and sleep. Alcohol strengthens the effect of GABA in the cortex, but the effects of certain prescription sedatives and hypnotics (diazepam, zolpidem or lorazepam) act in a similar manner that alcohol does.

Barbiturates, like Phenobarbital and anticonvulsant medications (gabapentin, lamotrigine or valproic acid) also increase GABA activity. Glutamate is the most important activating neurotransmitter of the brain, and it is also subjected to the effect of alcohol, but it is the opposite of GABA. Glutamate plays an important role in learning and memory, and plays a role in cell death when its level is too high. The positive effect of glutamate is reduced by alcohol consumption.

Acute alcohol use inhibits the release of glutamate, which influences the release of other neurotransmitters, such as dopamine, norepinephrine, and acetylcholine. Alcohol increases the sensitivity of the brain to glutamate, though. The process of up regulation increases tolerance, which means an increased amount of alcohol is needed for the increased production of GABA and dampening of glutamate. This may explain withdrawal symptoms, as well as a sudden increase of glutamate accounts for hyperactivity, psychosis and seizures.

Serotonin, a third neurotransmitter, is also affected by alcohol. Serotonin plays a role in anxiety, mood, appetite, and sexual functioning. Acute alcohol use and hallucinogens, such as LSD, mescaline and psilocybin increase serotonin activity of the brain. It also influences the activity of receptors of serotonin, increasing the activity of some and decreasing the activity of others. Chronic alcohol use decreases serotonin activity in the brain and causes the up-regulation of serotonin receptors, leading to tolerance and/or withdrawal symptoms, such as anxiety, insomnia or dysphoria.

Serotonin changes may be responsible for the nausea some people experience from alcohol. It is thought that antidepressant medications increase selective serotonin re-uptake inhibitors and decrease drinking behavior. Opiates are pain medications that are associated with addictions. Alcohol appears to increase the release of endogenous opiate beta-endorphin.

Dopamine is a neurotransmitter associated with the reward system of the brain, but also has a role in the attention and concentration processes of the brain, and also involuntary movements and hallucinations. Alcohol causes a boost in dopamine, which leads to euphoria and possibly contributes to addiction. The intoxicating effect of alcohol depends on its level in the blood. In non-alcoholic persons, 25 mg per deciliter indicate mild intoxication, which manifests in changes of mood, thinking and motor coordination. The level of 100 mg is where double vision, slurred speech and unsteady gait may appear. Levels of 500 mg may lead to respiratory arrest and death. Chronic use of alcohol can lead to tolerance, and much higher levels are causing the problems listed here.