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Neurochemicals: Demystifying Drug Abuse and The Brain’s Natural Reward System

Neurochemicals: Demystifying Drug Abuse and The Brain’s Natural Reward System

Author: Esther Wei M.A. MFT
Date: March 26, 2010

Have you ever used a credit card? Have you ever felt your mood lift after vigorous exercise? Have you ever felt comforted by eating one of your favorite foods? Have you ever worked really hard to meet a deadline and then feel exhausted for weeks afterwards, unable to be productive? Have you experienced a period of alertness after drinking coffee or some other caffeinated drink and then experience a crash, a period of fatigue and sluggishness when the caffeine has worn off? Have you ever had a sudden crying spell of intense emotions after you have participated in a highly emotionally charged event such as a wedding, or graduation?

Well, then you know something about how the brains biochemicals function and impact our emotional mood and our physical sense of well-being. Even if you’ve never tried using illicit drugs, every day we are using the same brain reward system in our everyday functioning. Illicit drugs and the high it provides takes advantage of the brain’s natural neurochemical reward system.

This article will explain on how drugs work in taking advantage of the brain’s inherent neurochemical reward system. It will clarify the myth that drugs themselves have magical powers to make people feel good. This article will also give an overview and introduction of neurochemicals in the brain. It will also help the reader understand the concepts of tolerance, upward/downward regulation, etc.

Neurochemicals. Neurochemicals are essential for brain functioning. They allow the brain’s nerve cells to communicate with each other in a series of electrical chemical relays. There are at least 60 different neurochemicals have been identified so far by scientists, and there are undoubtedly many more to be discovered. Examples of neurochemicals or neurotransmitters as they are also commonly referred, are dopamine, serotonin, norepinephrine, acetylcholine, and endorphins. Neurochemicals are critical for healthy brain functioning, and healthy brain functioning is critical for a person to function normally overall. Therefore, impacts on the levels of neurochemicals present in the brain greatly impact a person’s overall sense of well-being, including physically and emotionally and behaviorally.

The brain’s nerve cells produce the necessary neurochemicals needed for daily functioning and they produce them at a certain rate depending on the physiological and metabolic conditions and makeup of a certain person. A person will utilize their neurochemicals every day in their everyday activities. Other ways a person uses their brain’s neurochemicals is in feeling happy or sad, or needing to be alert to do something. And just like a person gets tired and needs to rest in order for his body to be restored, the brain also needs time to replenish its neurochemicals. The brain’s natural reward system also uses these neurochemicals. When a person feels good when they laugh, or eat something delicious, or have sex, or do something productive, or exercise, to name a few common activities, the brain releases the appropriate neurochemicals to make us feel good. The same system is in play when someone uses drugs.

Depletion. When we overdo it, whether it’s working too hard or undergoing a lot of stressors, or experiencing very intense emotions or drama, the brain could run low or be depleted of its stores of neurochemicals. And what happens when the brain runs low on these neurochemicals, well we feel terrible. We feel tired, irritated, sluggish and generally of no good use to anyone or to ourseves for a period of time. We generally feel low until our brains and our bodies have the chance to rest and replenish its store of neurochemicals. Of course, if the stressors or high drama continues on for a long period of time, then our bodies wear out or wear down, not having the opportunity to replenish or restore its needed neurochemicals. This depletion sets a person up for a host of psychological issues ranging from physical somatic symptoms, to depression, anxiety, or other psychological disorders.

How drugs work. While a popular perception is that psychoactive drugs themselves give users their “high”, or pleasurable sensation, it would be more precise to say that psychoactive drugs utilize or impact the brain’s own natural chemical reward system. The reinforcing properties of addictive drugs such as ethanol (alcohol), cocaine, amphetamine, opioids, and nicotine are associated with their ability to increase levels of neurotransmitters in critical brain areas (O’Brien, 2001, p.622). In fact, all classes of abused drugs reliably increase the extracellular dopamine in the nucleus accumbens areas in the brain and facilitate intracranial electrical self stimulation, making it easier for the rewarding effect to occur (Hull, 2002). This observation reinforces a prevalent theory of drug dependence that is based on the idea that all addictive drugs stimulate dopamine neurons in the brain’s mesolimbic system (Ray & Ksir, 2004).

No free lunch. Using drugs is analogous to using a credit card. When a person uses drugs, the drugs activate the brain to use up more neurochemicals than it would normally use during a certain period of time. Just like when we use a credit card, we use money in advance that we eventually need to pay back. So when a person uses drugs, while they feel good temporarily because they are forcing the brain to dump neurochemicals, eventually when the high wears off, the person will need to “pay themselves back” in the form of a resting period where the person experiences a neurochemically depleted state. This neurochemical depleted state usually entails low mood, low energy, low productivity and in generalized “crummy-ness”.

Tolerance. Homeostasis refers to a healthy level of functioning for the human body, (e.g. body temperature, heart rate and blood pressure). When homeostasis is disturbed under stressful conditions, a person’s biological systems will tend to make adjustments to return the back to homeostasis. This tendency to try to return to homeostasis is similar at the neurochemical level. If a drug’s effects cause too much neurotransmitter molecules to be available, a decrease in receptor sites can be observed. Known as “downward regulation”, this adjustment contributes to developing tolerance towards that drug because it takes more and more of a drug to achieve the same effects. An example would be when heroin consistently occupies the brain’s opiod receptor sites. Conversely, when a drug’s effects cause too few neurotransmitter molecules to be available, an increase in receptor sites can be observed in process known as “upward regulation” where the receptor sites gain heightened sensitivity to that type of neurotransmitter because of the previous deprivation.

Rebound effect. The implications of upward and downward regulation is that over time, a person’s brain tries to dampen and counter the effects of regular long term use of a psychoactive drug. One can see this mechanism in action not only in the development of tolerance but also when a person goes through withdrawal from a drug. If the drug’s primary action was depressive in nature (e.g. alcohol), during withdrawal, the body bounces back with heightened elevated mood. Conversely, if the drug’s primary action is excitatory in nature (e.g. methamphetamine), during withdrawal, the body tends to bounce back with a depressed mood.

The King Kong Brain. The cerebral cortex, the top and sides of the upper part of the brain, is responsible for higher mental processes such as reasoning and language and is less active when a person is asleep or under sedating drugs. The “survival”, lower, or “King Kong” brain (includes the structures of the limbic system or “emotional brain”, hypothalamus, midbrain, pons, medulla and lower brain stem), is active whether a person is asleep or not and is responsible for important mechanisms for behavioral control important for survival (i.e. emotions, feeding, drinking, temperature regulation, sexual behavior, reflexes, breathing) (Ksir & Oakley, 2004; Preston, O’Neal & Talaga, 2005).

Imprinting is the brain’s learning process where neurons that “fire together, wire together” to form enduring pathways in the brain (Schwartz & Begley, 2002). This process can be liked to how traveling over the same dirt road leaves ruts and makes it easier to stay on track on subsequent trips. For example, learning to tie one’s shoes or ride a bike uses this same process. When certain actions are repeated enough, the series of behaviors or thoughts can become automatic or like second nature. Experiences associated with fear, stress or emotions such as traumas and addictions are typically imprinted in the survival brain.

While one can often use the upper brain’s logic and reasoning to override the survival brain, one cannot beat the survival brain, or “King Kong” all the time. The imprints in “King Kong” may be awakened at a vulnerable moment and overwhelm a person’s rational decision-making process. When one is dealing with addicts, compulsive behaviors, or a fear-based response, one needs to understand that you are up against a powerful “King Kong”.

This article addressed the importance of the brain’s neurochemicals in everyday functioning. It also introduced the notion of neurochemical depletion and described how drugs utilize the brain’s natural reward system, how the body becomes habituated to long-term drug usage. Finally it discussed rebound effects and the “King Kong” brain.

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O’Brien, C. P. (2001). Drug addiction and drug abuse. Hardman, J.G., Limbird, L. E. & Gilman, A. G. (Eds.), Goodman & Gilman’s pharmacological basis of therapeutics (pp. 621-642). New York, NY: McGraw-Hill Companies, Inc.

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