Naked Science Forum
General Science => Question of the Week => Topic started by: Adam Murphy on 18/02/2019 17:04:05
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Donald wants to know:
"How does ethanol interact with the brain and why does it disproportionately effect the area involved in behaviour and movement rather than the parts of the brain involved in vision, hearing, touch or the brainstem involved in breathing, blood pressure and heart rate?"
What do you think?
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As far as I know, the exact mechanisms of alcohol intoxication are not known. However, it appears that the primary effects are related to potentiation of GABA pathways in the brain (so many of the effects are similar to those of benzodiazepines, GHB/GBL, gabapentin, and barbiturates, each of which potentiates or activates this pathway in different ways.)
Unlike these other drugs, especially benzos, which are quite potent and selective (a 2 mg dose of valium wouldn't be unusual), alcohol is very weak and unselective--requiring doses typically measured in ounces or deciliters!
As I understand it, activating GABA pathways dampens other signals in the brain--with the effects manifesting more strongly for processes that require more neurons (especially if thee neurons are in different parts of the brain). This means that just a little bit of alcohol can potentiate the GABA pathways a little bit, causing the most change in higher cognitive functions like reasoning and self-control. As the dosage increases, the effects there increase, and it also starts manifesting in fine motor control and response time. When really large doses are reached, even the ability to breath can be compromised.
Acute toxicity of alcohol (for a single large dose) can largely be attributed to loss of the ability to regulate breathing, or aspiration of vomit. But most injuries and deaths due to acute alcohol intoxication are due to loss of gross motor skills and response time, especially when it comes to things like automobiles and stairs...
However, much of the harm from alcohol is not from acute, but rather chronic abuse. Because the dosage is so high, alcohol is very hard on the liver and kidneys. Also, the neural pathways that alcohol acts on become resistant, then accustomed to and then dependent on the alcohol. Those who drink excessively for a long time can suffer from the potentially fatal DTs (delerium tremens), which can cause hallucinations and seizures (both of which can be treated with some of the GABA potentiators mentioned earlier).
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Apparently, GABA is expressed in several forms on nerve cells, and it is the δ-form of GABA that is most sensitive to alcohol.
Alcohol can suppress processing of glucose, producing a hypoglycaemic attack (such as occurs with diabetes).
See: https://en.wikipedia.org/wiki/Alcohol_intoxication
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Twin studies and family studies have shown a strong genetic contribution to alcoholism(40-60%), but that still leaves a lot of environmental influence.
- Some tribes/races have a different tendency towards alcoholism on a population basis
A number of genetic variants have been identified that make a small contribution towards alcoholism (or addiction in general).
See: https://en.wikipedia.org/wiki/Addiction#Genetic_factors
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It seems to me that the interesting question isn't "why does alcohol cause drunkenness?"
It's easy to say that the brain's complex . Perturbing it with chemicals messes up how it works. We see that change and label it "drunk".
The more interesting question is why do the other nerves keep working?
Drunks can still hear and see, they can still taste food and smell stuff.
How come those bits of the nervous system keep working more or less OK?
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Let's focus on the question, rather than what the question ought to be. "Why does alcohol make you drunk ?". The answer obviously depends on who 'you' is. (Yes, 'is'.) Obviously, I can only answer on behalf of me. Think about how boring that would be to just about everybody else on the planet, if they had even read this far. Sorry to disappoint so few people, but alcohol doesn't do it for me. Only I can make me drink, and no-one has ever wanted to drink me, which would make me drunk. So drink up, drink up, and use an Uber or some other taxi of friend, if you still have the sense. Cheers, Alan M, Seaforth.
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Let's focus on the question, rather than what the question ought to be. "Why does alcohol make you drunk ?". The answer obviously depends on who 'you' is. (Yes, 'is'.) Obviously, I can only answer on behalf of me. Think about how boring that would be to just about everybody else on the planet, if they had even read this far. Sorry to disappoint so few people, but alcohol doesn't do it for me. Only I can make me drink, and no-one has ever wanted to drink me, which would make me drunk. So drink up, drink up, and use an Uber or some other taxi of friend, if you still have the sense. Cheers, Alan M, Seaforth.
Were you sober when you wrote that?