Neurotransmitters and Addiction

This is the fourth installment of a five part series on the neurobiology of addiction by Jennifer Fernández, PhD. Follow along on Power Over Addiction or Facebook.


Drugs act on neurotransmitters to increase, decrease, or alter their release or reuptake.

Drugs act on neurotransmitters to increase, decrease, or alter their release or reuptake.

In the previous installment of this series, we learned that dopamine is responsible for feelings of pleasure and euphoria, but it has other functions as well. And dopamine isn’t the only chemical messenger in the brain.

Dopamine is just one of dozens of neurotransmitters. It is the most well known chemical messenger and is responsible for feelings of pleasure, coordination of movement, and logical thinking. It is responsible for “the rush” one feels when they use a recreational drug and it also influences the addictive potential of a drug. It is released when we do things that are important for survival, like sleeping, eating, and having sex. Dopamine sends the message “That feels good! Do it again!”

Norepinephine is one of the brain’s natural stimulants. It is responsible for increased alertness and focus and is involved with learning and memory processes. Norepinephrine is also involved in the fight or flight response. It signals the release of adrenaline in your body to prepare you for survival in the face of imminent danger. It sends the message “Fight!” or “Run!”

GABA (gamma-aminobutyric acid) is the brain’s Valium. It relaxes the brain by suppressing overexcitement or hyperactivity, while allowing us to remain alert and focused. Low levels of GABA are associated with anxiety and seizure.

Glutamate stimulates various activities throughout the brain. We don’t know much about how it is involved in mood regulation.

Serotonin plays several complex roles in the brain. It is involved in regulating mood, sleep, appetite, and sex drive. Low levels of serotonin are associated with aggression, irritability, and depression. Serotonin is also responsible for hallucinations and regulating other neurotransmitters.

Endorphins are the brain’s natural opiates. They influence the perception and control of physical and emotional pain. In addition to pain relief, they are responsible for feelings of well-being, happiness, and euphoria.

Drugs act on these messenger chemicals to increase, decrease, or alter their release or reuptake. Our brain is wired to recognize these chemicals and accept their messages. The difference is that drugs relay the message better, faster, and in a much more intense way. Research shows us that life experiences affect the development of the brain, including how neurotransmitters work. For example, someone who has experienced trauma may find it difficult to feel pleasure or regulate their mood due to low levels of dopamine and serotonin. This may cause them to turn to externally supplied chemicals to balance the levels of neurotransmitters in their brain.

The next, and final, installment of this series will explain why some people turn to recreational drugs in an attempt to balance the chemical messengers of the brain.

Photo credit: Life Mental Health

This is your brain on drugs. For real.

This is the third installment of a five part series on the neurobiology of addiction by Jennifer Fernández, PhD. Follow along on Power Over Addiction or Facebook.


This is not your brain on drugs. These are burnt eggs.

This is not your brain on drugs. These are burnt eggs.

Addiction is scary. It has caused pain in many people’s lives and has cost families and governments trillions of dollars to treat and prevent. It’s no surprise that social service agencies want to educate the general population about the harms of addiction. You may have seen this public service announcement comparing the addicted brain to fried eggs. The image is powerful, yes, but it is not educational. This is what actually happens in your brain when you take drugs.

Neurons generate messages that travel between cells in the brain.

Neurons generate messages that travel between cells in the brain.

Above is an image of a neuron. Our brain is filled with billions of these nerve cells and fibers. They contain genetic information and also serve as messengers. They transmit information through fibers from one cell to another via electrical charges. Neurons generate messenger chemicals, or neurotransmitters, to transmit information from cell to cell. The electrical charge travels through the dendrites, cell body (or soma), axon, and terminal bud down to the synapse, the gap between neurons where the magic happens. Neurotransmitters live in the terminal bud of neurons. An electrical charge comes through the neuron and releases the messenger chemicals. The chemicals then float across the synapse and attach to the neighboring cell for a short amount of time in a process called neurotransmission. Once the message has been relayed, they return to their home cell. This process is called reuptake. For example, if you were to burn your hand on the stove, nerve cells in your muscles would send a message to the neurons in your brain saying, “Ouch!” Your brain sends a message back down to the muscles in your arm to pull your hand back. At the same time, the message from your burning hand also alerts your brain to release endorphins, the brain’s natural pain reliever. The endorphins do their job and relieve the pain long enough so you can think to run cold water over your hand. Once the message has been communicated, the endorphins return to their home cell until the next electrical charge commands them to be released.

 

THIS is your brain on drugs.

THIS is your brain on drugs.

Above we have a close up of the synapse, the gap between neurons, and what happens when cocaine is present in the brain. The red arrows show the process of reuptake. The neurotransmitter dopamine has been released into the synapse to send a message to the neighboring cell. Once dopamine has completed its task, it attempts to go back home, but cocaine is blocking the way. Since dopamine can’t go back home it goes back to doing it’s job, binding to the neighboring cell. Dopamine’s loitering, so to speak, is what causes feelings of intense pleasure and euphoria.

Dopamine is only one of dozens of neurotransmitters in the brain. In the next installment, we identify the major neurotransmitters involved with drug use.

Photo credits: burnt eggs by incredibledictu, neuron, and neurotransmission by NIH

 

Zap away cocaine addiction with lasers! or magnets!

brain laserResearchers at the National Institute of Health and UCSF claim to have stopped and started cocaine addiction in rats with the use of laser stimulation to the prefrontal cortex, the brain region where decision making and impulse control take place. “When we turn on a laser light in the prelimbic region of the prefrontal cortex, the compulsive cocaine seeking is gone,” said Antonello Bonci, MD, scientific director of the research program at the NIH’s National Institute on Drug Abuse (NIDA).

Studies with human subjects are already being designed ,according to Billy Chen, the lead researcher. But lasers wouldn’t be used with human participants. Prefrontal cortex stimulation would be achieved through the use of transcranial magnetic stimulation (TMS) which is currently being used as a treatment for depression. It should be noted that the jury is still out on the efficacy of TMS to treat depression, as reported in the journals Current Pharmaceutical Design and Pharmacology and Therapeutics.

This is all very interesting, but addiction is more than biological. People don’t become addicted to a drug because of their neuroanatomy and neurochemical environment. It’s more complex than that. It seems unclear to me what exactly changes in the prefrontal cortex due to this stimulation. Does it make a person (or a rat) more mature and logical in their decision making process? If that’s the case, there may be many uses for this technology! Needless to say, I’m skeptical.

You can read the abstract and view supplemental information about the study in Nature.

Thanks to Jim Wiggins for sharing this article.

Photo credit: Block and Tackle Productions

Drug Tolerance Explained

toleranceOur brain thrives on novelty and dopamine helps us store information about novel situations.  We know that dopamine is released when we receive a reward, but it is also involved in noting unexpected rewards. If you get more juice than you anticipated, your brain releases dopamine and sends it to the anterior cingulate in your frontal cortex, a brain region responsible for anticipating rewards and making decisions. Get less juice than you anticipated and, again, your brain will encode the information, but this time, by sending less dopamine to the anterior cingulate. If you get the same amount of juice you expected, no dopamine is released. This mechanism enables us to recognize patterns and learn which behaviors lead to risk versus reward.

How does this translate into drug and behavioral tolerance? When you use cocaine for the first time, your brain registers it as a pleasurable experience. After using it a few more times, you might notice that you don’t experience the same level of euphoria as before. That’s because the experience has lost novelty and your brain has learned to recognize the pattern. In other words, dopamine isn’t released since there isn’t anything novel about the experience. Tolerance is born. In order to achieve euphoria from cocaine, you must now use more.

The same process occurs with compulsive behaviors. The first few times you shoplift (and don’t get caught) you experience relief and pleasure, but with subsequent trials you notice a decrease in the euphoria you experience. So, you start shoplifting more frequently.

NoteThere are many neurobiological mechanisms at play in addiction and compulsive behaviors and the role of dopamine in addiction and tolerance is just one facet of a complex biopsychosocial phenomenon.