Etiology and Maintenance of Substance Addiction bu Dopamine

Drug Addiction: A Look into Dopamine's Role

The dependence on a legal or illicit drug or prescription to function normally is referred to as drug addiction/substance dependence. Addiction impairs an individual's ability to control drug usage, regardless of the harm it causes. The National Institute on Drug Abuse (NIDA) classifies addiction as a brain illness since it alters the structure and function of the brain. Drug addiction is a chronically relapsing illness characterized by urge to seek and consume the drug, lack of control in limiting drug consumption, and the establishment of a negative emotional state such as anxiety, among other things.Research studies in the recent decades have established addiction as a matter of brain chemistry rather than a weakness in character. The naturally-occurring neurotransmitter, dopamine, is connected to the process of drug addiction. This essay aims at discussing the role that dopamine plays in causing and maintaining substance addiction.

The Role of Dopamine in Substance Addiction

Dopamine is a naturally-occurring neurotransmitter which modulates the ability of the brain to perceive reward reinforcement (Di Chiara, & Bassareo, 2007). Elevation of dopamine levels results in pleasure sensation to the brain which creates a motivation to proactively undertake tasks that are critical to our survival, for instance, eating. Dopamine is responsible for conditioning us to do the things we need to do for survival. This is the same way that drug addiction starts and is maintained. Use of an addictive drug fills the limbic brain with dopamine, raising it to as much as five to ten times the normal level. With this elevation, the brain of the user starts to associate the drug with an outsize neurochemical reward. Using the drugs over time artificially raises the amount of dopamine that the brain think is normal, thereby creating a need that only they (drugs) can meet. According to Dr. Nora Volkow, the director of NIDA, a drug that leads to an increase in dopamine in the limbic areas of the brain causes the brain to recognize that signal as something that is very reinforcing; thus the brain will learn it very rapidly. Exposure to that stimuli will stir up an immediate desire for that particular drug since the brain has mastered it as a reinforcement. Over time, the considerably high levels of dopamine will create plastic changes to the brain, desensitize neurons, and decrease the number of receptors such that they are less affected by it. This leaves the user with a loss of control and an intense compulsion to take the drug, which is the state of addiction.

The Addictive Nature of Dopamine-Producing Drugs

Dopamine-producing drugs are the most addictive. This, according to Dr. Volkow, is because the drugs can fill a need for more dopamine constantly. Each intake of the drug increases the level of dopamine such that the desire for the drug becomes insatiable (Volkow et al. 2007). The value of the drug to the user keeps increasing, eventually hijacking the functioning of the dopamine system. The user will, therefore, increase the intake of the drug over time to keep up with the elevated levels of dopamine. This explains the cycle of addiction whereby a user begins with a single shot of drugs but increases in the intake due to the increased levels of dopamine resulting from each intake. However, this addiction results in the overwhelming of the brain receptors and the brain responds by lowering the production of dopamine or eliminating dopamine receptors. These adaptations minimize the effect of dopamine on the reward center of the brain. This explains why people with an addiction realize that the initially desired substance no longer provides them as much pleasure and they have to take more to obtain the same dopamine "high" since their brains have adapted, an effect referred to as tolerance.

The Role of Dopamine in Relapse

There is an increased possibility of relapsing for an addicted person associated with the roles played by dopamine. Besides the creation of pleasure, dopamine is also involved in learning and memory, which are key elements of the transition from liking something to being addicted to it. Even at the point where tolerance is achieved, the brain has stored memory concerning the environmental cues associated with the desired substance, such that it can be located again. These memories aid in creating a conditioned response, an intense craving, any time the person these environmental cues (Volkow et al. 2011). Cravings are contributors to both addiction and relapse after periods of sobriety. For example, a person addicted to alcohol might sink back into drinking after seeing a bottle of whiskey. Conditioned learning of the brain facilitated by dopamine explains why people who have developed an addiction face the risk of relapsing even after years of exercising abstinence.

Theories and Approaches to Understanding Addiction

Various theories and approaches have been taken in an attempt to explain why people become addicted to drugs. These approaches have been categorized into neuroscientific theories and psychological theories (Gifford & Humphreys, 2007). Neuroscientific theories base their explanation on the understanding of the effects of drugs on the brain, which entails the two major pathways of action – the dopamine reward system and the endogenous opioid system. The dopamine reward system is as have been explained above. The endogenous opioid system of the brain is also linked to drug use and misuse. Exogenous opiate drugs such as heroin and morphine perform the function of opiate receptor agonists, readily causing tolerance and dependence. With chronic opiate use, an adaptation of the opiate receptors occurs quite readily, for instance as evidenced by the need to use larger amounts of morphine to relieve pain. Research is indicating the possibility of the opioid system being involved in the rewarding effects of other psychoactive substances. Theorists have separated the functions of the dopaminergic and the opioid systems. The dopaminergic system is associated with the incentive, preparatory aspects of reward, experienced as thrill, urgency, or craving, while the opioid pathway is associated with the satiation and consummatory aspects of reward such as rest, blissfulness, and sedation.

Other explanations to addiction include the psychological theories/approaches which are linked to behavioral aspects, personalities, and rational choices. Behavioral models explain that behavior is maintained by the consequences of such behavior. Most dopamine-producing drugs will result in some brain reinforcement which will increase the desire to take more. Some theorists argue that there are individuals with an addictive personality which explains their addiction (Dagher & Robbins 2009). For such people, dependence holds benefits initially before adverse effects kick in. Rational choice theories explain why people with an addiction continue to use the substances even when it is against their intention.

Conclusion

In conclusion, dopamine plays a vital role in the etiology and maintenance of substance addiction. It is involved in the creation of pleasure, learning and memory storage. In general, dopamine modulates the ability of the brain to perceive reward reinforcement. Dopamine-producing drugs are most addictive since they increase the levels of dopamine in the brain creating a need to take more. The learning and memory aspect of dopamine is responsible for the creation of craving and the possibility of a relapse after an extended period of sobriety once an individual is exposed to the drug stimuli or the environmental cues related to the drug.

References

Bickel, W. K., Miller, M. L., Yi, R., Kowal, B. P., Lindquist, D. M., & Pitcock, J. A. (2007). Behavioral and neuroeconomics of drug addiction: competing neural systems and temporal discounting processes. Drug and alcohol dependence, 90, S85-S91.

Dagher, A., & Robbins, T. W. (2009). Personality, addiction, dopamine: insights from Parkinson's disease. Neuron, 61(4), 502-510.

Di Chiara, G., & Bassareo, V. (2007). Reward system and addiction: what dopamine does and doesn’t do. Current opinion in pharmacology, 7(1), 69-76.

Gifford, E., & Humphreys, K. (2007). The psychological science of addiction. Addiction, 102(3), 352-361.

Thomas, M. J., Kalivas, P. W., & Shaham, Y. (2008). Neuroplasticity in the mesolimbic dopamine system and cocaine addiction. British journal of pharmacology, 154(2), 327-342.

Volkow, N. D., Wang, G. J., Fowler, J. S., Tomasi, D., & Telang, F. (2011). Addiction: beyond dopamine reward circuitry. Proceedings of the National Academy of Sciences, 108(37), 15037-15042.

Volkow, N. D., Fowler, J. S., Wang, G. J., Swanson, J. M., & Telang, F. (2007). Dopamine in drug abuse and addiction: results of imaging studies and treatment implications. Archives of Neurology, 64(11), 1575-1579.

West, R., & Brown, J. (2013). Theory of addiction. John Wiley & Sons.