The Addictive Brain as taught by Professor Thad A. Polk Part II

This is a continuation of the blog started on December 5th. Summaries of the 4th – 6th lectures are presented here. Please read the blog from the 5th first if you haven’t read them yet.

Lecture 4: Genetics—Born to Be an Addict?

In this lecture much detail in genetics and various scientific studies discussed. This much detail not needed to understand the basic points.

1.  Some people more at risk of addiction than others due to genetic susceptibility. Genetic susceptibility does not mean that they will become addicted. Nor does it mean if they do become addicted they can’t recover.

2.  Many genes are involved in inheriting the genetic susceptibility.

3.  Many of the genes contribute to the susceptibility of addiction to a variety of substances.

4.  Scientists are learning more about what the different genes are doing and may allow for tailoring of treatments. For instance, some people are more likely to be helped by naltrexone than others depending on their genetic makeup.

Lecture 5: Your Brain on Drugs

This lecture focuses on 3 questions, first is how can drugs cause pleasant sensations or change our mood. next is how are some drugs more potent than others and last, how do we get dependent on drugs.

To understand how drugs work the lecture starts out with a basic explanation of how neurons work. Neurons communicate by means of what is called neurotransmitters. Chemicals that activate neuronal signals. Serotonin and dopamine are examples. Neurons communicate by releasing neurotransmitters and nearby neurons have neurotransmitter receptor sites. An analogy is made that neurotransmitters and receptors have a lock and key arrangement. Certain receptors are only activated by certain neurotransmitters.

Question 1) How do psychoactive drugs produce psychological effects? Psychoactive drugs imitate natural neurotransmitters. They act as a key to activate neurons. The more drugs in the brain, the more stimulation of receptors.

Question 2) Why are some drugs stronger than others? Has to do with affinity. – How well the key fits in the lock. If the drug fits well in the receptor, the more neuronal stimulation will occur. He then defines two terms, agonist and antagonist. An agonist is a chemical that binds to a receptor and activates it. The key fits and activated the neuron. An antagonist is a chemical that binds to the receptor but doesn’t activate it. The key fits but doesn’t activate the neuron. Naltrexone is a drug that binds to receptors but doesn’t activate the neuron and also blocks the drug that normally activates the cell.

Question 3) How can someone get dependent of drugs? One mechanism is that as your brain is repeatedly exposed to drugs your brain will compensate by making less receptors available for stimulation. Hence you will need larger doses for the same effect.

Lecture 6: Coffee and Cigarettes

The next several lectures focuses on specific drugs and how they work and possible treatments. He starts with two common and legal drugs, caffeine and nicotine.

Caffeine – Works by being an antagonist of adenosine. Binds to adenosine receptors but doesn’t active the neurons. Adenosine is inhibitor of neural activity, therefore your brain is a little more alert. People do develop a tolerance and can have withdrawal symptoms such as headache. Little medical consequences. Not highly addictive.

Nicotine – Smoking is responsible for dopamine release in the VTA. (Ventral Tegmental Area as discussed in lecture 3.) Hence it is one of the most addictive substances known. Smoking causes mild psychological effects similar to caffeine but has unfortunate health consequences. There are some options for medically assisted therapy for quitting smoking. One is nicotine replacement like patches or gum. Behavioral therapy for avoiding triggers and coping with urges. Verinicline (Chantix) is a partial agonist of nicotine and can lessen withdrawal symptoms.


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