Updated: Dec 9, 2020
NEUROBIOLOGY OF DEPENDENCE & ALCOHOL-RELATED BRAIN DAMAGE
St. Xavier's College (Autonomous),
Mumbai, Maharashtra, India
Do you find yourself indulging in a glass of wine now and then? Alcohol does seem to perk people up and helps to socialise at parties. Well, you are not alone. Studies show over 86 % of people aged 18 or older have reported drinking at some point in their lives. Occasional drin
king doesn’t seem to cause any problem, but moderate or heavy drinking can cause deficits over time. When our body ingests alcohol, it starts traveling from our stomach & intestine via our bloodstream to various organs. Once it passes through the blood-brain barrier it directly affects the brain’s neurons and slows down their signaling due to which we begin to feel its depressant effect.
Your Brain On Alcohol:– There are a few stages of alcohol consumption:
· Euphoria – Here the release of dopamine is increased that creates a pleasurable sensation along with a minor impairment of reasoning and memory.
· Memory loss, depression, and distortion – Once the blood alcohol level crosses 0.05 Blood Alcohol Content (BAC) blood and body tissue begin absorbing the extra alcohol then euphoria turns into depression.
· Excitement – You are legally intoxicated when the BAC ranges from 0.09 to 0.25. At this level, the deficits that you experience are due to impairment of the occipital, temporal and frontal lobe, including blurred vision, slurred hearing and speech, and lack of control, respectively. The parietal lobe is also affected causing loss of motor skills and slower reaction time.
· Confusion – Now your cerebellum that helps with coordination is impacted when the BAC reaches 0.18 to 0.3 and you might need help in walking and standing. Also blackouts, loss of memory or consciousness occurs at this stage because the hippocampus gets affected at this stage which is responsible for making new memories.
· Stupor – At this stage of BAC of around 0.25 to 0.40, there might be concerning symptoms of alcohol poisoning.
· Coma & Death – At a BAC of 0.35, you might go into a coma due to compromised respiration and circulation and a BAC over that leads to death.
How Much Is Too Much?
1. Occasional drinkers – Here short-term effects are produced after one or more drinks. A high volume of alcohol on empty stomach results in a blackout. Also poor decision making like driving under the influence.
2. Moderate drinkers – Those who consume one or more drinks daily. It can lead to high risk of breast cancer along with violence, falls, and car accidents.
3. Heavy and chronic drinking – It is drinking heavily over an extended period. For women, it is more than 3 drinks on any day or seven days per week. While for men, it’s either 4 drinks per day or 14 per week. For reference, a bottle of wine is equivalent to 5 drinks.
Neurobiology Of Alcohol Dependence:-
Alcohol starts to act on the receptor sites for its neurotransmitters (chemical messengers) such as GABA, dopamine, and glutamate. Alcohol is said to have both positive and negative reinforcing nature on the brain. Now the positive action comes from the activation of the Dopaminergic Reward Pathway present in the limbic system. What’s Dopamine? It is a neuromodulating compound that is released in the Ventral Tegmental Area (VTA) and extends to the Nucleus Accumbens (NA) where it is involved in motivation & reinforcement behaviors.
The brain’s major inhibitory neurotransmitter is GABA and excitatory is Glutamate. Alcohol increases the GABA release by acting presynaptically at the GABA neuron and also decreases the glutamate levels in the Nucleus Accumbens and the amygdala suppresses the glutamate-mediated signal transmission in the central nucleus. Opioids like endorphins, dynorphins influences drinking behavior by interacting with the mesolimbic system. Ethanol on breakdown gives acetaldehyde as a primary product. Acetaldehyde is a highly reactive compound that reacts with dopamine and serotonin in the brain. These reactions produce alkaloids like Salsolinol that are responsible for the physiological and behavioral effects of alcohol.
Types of alcohol-related brain damage:-
The well-known term “wet brain” comes under “ Wernicke - Korsakoff Syndrome” (WKS). It comprises two forms of dementia but those with Alcohol Use Disorder (AUD) are mostly malnourished due to a poor diet. Since alcohol blocks a person’s ability to absorb or use the vitamin it leads to a thiamine deficiency, many develop this damage due to years of heavy drinking. Some of its symptoms include - confusion, paralysis of eye muscles, forgetfulness, etc.
Another type of brain damage is Hepatic Encephalopathy it is inflammation of the liver. As we know the liver is responsible for filtering out toxins if the liver gets affected then bad blood is sent to the brain which leads to a buildup of toxins in the brain. Symptoms include – altered mood or personality, anxiety, depression, etc.
Lastly, alcohol-related brain damage is also observed in infants known as Fetal Alcohol Syndrome (FAS). Alcohol travels via the umbilical cord to the fetus, and the underdeveloped body is not able to process the toxin. This can lead to disorders like miscarriage, distinct facial features, low IQ, poor vision or hearing, etc.
As of now, there are no cures for alcohol-related brain damage. In the case of WKS, thiamine & vitamin supplements are provided to improve functioning. For Alcoholic Hepatitis lifestyle changes might reverse the deterioration. But quitting drinking is the best first step to overcome the damage. Most medical professionals recommend a rehab facility. When proper detox, abstinence, and a healthy diet are followed some of the ill effects are undone. Acamprosate and Naltrexone are prescribed to prevent the effects of relapse or to lower alcohol craving.
Alcoholics are not all alike the effects differ from person to person. Excessive consumption of alcohol leads to structural changes in certain parts of the brain and functional changes to neurotransmitter pathways which causes impairments to behaviour & cognition. But advancements are happening in the world of addiction that might help to prevent it and other brain-related damage.
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Image References –
· Image 2 – shows the regions of the brain affected by alcohol.