Alcohol and it’s Effects on the Brain
Alcohol can make you laugh or it can make you cry, it can make you lively or make you sleepy, it can boost your confidence or make you act the fool. How can alcohol have all these different effects on people? If we want to know how alcohol affects our moods and behaviors we must first understand a bit about how the brain works.
The human brain is made up of about 100 billion nerve cells (also known as neurons). Everything that we think, feel or do is the result of electrical signals passing back and forth between neurons. These electrical signals require the help of chemicals called neurotransmitters in order to pass from neuron to neuron. Scientists have identified around 60 different neurotransmitters so far and tell us that there are probably many more yet to be identified.
Different neurotransmitters have different effects in the brain. For example, serotonin is connected with mood. People suffering from clinical depression tend to have a shortage of serotonin in their brains, and medications like Prozac can help to alleviate depression by increasing the availability of serotonin in the brain. Endorphins are a class of neurotransmitters which act as the brain’s natural painkillers.
Electrical signals in the brain are transmitted in the following manner: The neuron which is sending the electrical signal releases a neurotransmitter, and the neuron which is receiving the electrical signal accepts the neurotransmitter at a site which is called a receptor. When the neurotransmitter from the first neuron chemically binds to the receptor of the second neuron the electrical signal is transmitted. Neurotransmitters and receptors work like locks and keys: there is at least one different receptor for each different neurotransmitter. For example, an endorphin receptor can only be triggered by and endorphin, a serotonin receptor can only be triggered by serotonin, and so on. Different neurons have different receptors. Some neurons will only be triggered by serotonin, some only by an endorphin, and so on for all the different neurotransmitters.
Okay–now what does all of this have to do with alcohol?
Every mood altering substance from heroin to coffee has an effect on the neurotransmitter system of the brain. Some psychoactive drugs affect only one specific neurotransmitter system, whereas others affect many. Morphine, for example, mimics the neurotransmitter beta-endorphin–a natural painkiller found in the brain. Morphine is shaped like beta-endorphin and binds to the beta-endorphin receptors thus acting as a painkiller and also giving rise to feelings of pleasure. Caffeine is shaped like Adenosine and acts on the adenosine receptors. Alcohol on the other hand affects many different neurotransmitters, not just one, Why is this?
Morphine and caffeine are both large molecules. Neurotransmitters are also large molecules. Morphine and caffeine have the effects which they do because of their similarity in shape to neurotransmitters which occur naturally in the brain. Alcohol on the other hand is a quite small molecule. Alcohol does not mimic a neurotransmitter. So then how does alcohol affect neurotransmitters?
Alcohol is a fat soluble molecule. Fats (called lipids) are a major component of all cell membranes, including the cell membranes of neurons. Alcohol enters the cell membranes of neurons and changes their properties. Receptors are located on cell membranes and this means that receptor properties are altered by the presence of alcohol. Cell membranes also control the release of neurotransmitters and this means that the release of neurotransmitters is also affected by the presence of alcohol.
The effects of alcohol on receptors and neurotransmitters have been well documented for several neurotransmitters and their corresponding receptors. These effects are summarized in Table 1.
Table 1: Alcohol’s Effect on Neurotransmitters and Receptors
Glutamate
Alcohol inhibits glutamate receptor function
This causes muscular relaxation, discoordination, slurred speech, staggering, memory disruption, and blackouts
Ether and chloroform have similar effects on the glutamate system
GABA (gamma-aminobutyric acid)
Alcohol enhances GABA receptor function
This causes feelings of calm, anxiety-reduction and sleep
Valium has a similar effect on the GABA system
Dopamine
Alcohol raises dopamine levels
This leads to excitement and stimulation
Cocaine and amphetamine have similar effects on the dopamine system
Endorphins
Alcohol raises endorphin levels
This kills pain and leads to an endorphin “high”
Morphine and heroin have similar effects on the endorphin system
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