NEUROBIOLOGY & NEUROPHYSIOLOGY OF ADDICTION
The idea of “reward” is central to understanding the neurobiology of addiction. In addition, the frontal lobe, and others, are involved in inhibition and are likely involved in in the development of addiction, and its consequences.
Animals and other organisms respond to behaviors that create rewarding behavior, for things like food, sex, shelter, exercise, and forming bonds. Because these behaviors are necessary for life, the nervous system acts in a way to reward these positive behaviors by releasing dopamine causing the person to experience pleasurable sensations. This is a way of producing positive reinforcement for desirable life-sustaining actions.
There are also non-natural substances and behaviors that create the released of dopamine. Since pleasurable feelings will be developed after the behavior, the brain believes that the behavior is life-sustaining and positive. But, what is happening is that these non-natural substances – rather they be a food source or a mood-altering drug – create positive reinforcement from a negative, and potentially harmful behavior.
Many mood-altering drugs work directly or indirectly on this dopamine-induced reward pathway. Once this pathway is established, the brain will automatically seek to continue its activation, but using the substance or behavior that is the most power and most readily available. Alcohol also affects this dopamine system, driving the alcoholic to continue drinking with abandon.
The prefrontal cortex is also involved in the reward pathway, and there are connections to the primitive brain, responsible to the regulation of dopamine from the prefrontal cortex into the ventral tegmental area (VTA), and the nucleus accumbens. What is to important is not to remember each of these scientific terms, but to understand that there is a reward pathway and it involves multiple areas of the brain.
By understanding these pathways, scientists and doctor’s have been able to develop better treatments for substance abuse, whether it be a medication or another effective intervention, such as therapy. This pathway was, in part, discovered by allowing rats to self-administer substances. When this pathway is activated in the rat by electrical discharges to some parts of the brain, the rat will attempt to continue to self-administer the substance. But, when this reward pathway is blocked from activation by chemicals or another area, not related to this pathway is electrically stimulated, the rat does not continue the addictive behavior.
This is part of the reason why addiction is defined exhibiting a compulsive behavior, even if negative consequences can be expected. Another hallmark in addiction is the inability to control the intake of the pleasurable substance, despite the potential for self-harm or harm to others. In fact, it is the reward pathway (among others) that is likely to be responsible for the development of cravings.
Some drugs like opiates, directly affect the release of dopamine by binding to certain receptors in the reward pathway. Others, such as cocaine bind to receptors in the nucleus accumbens and VTA, which are part of the reward pathway, and prevent these receptors from “cleaning up” the dopamine from the receptor area. Now, the dopamine is free to exert its actions, but creating craving, euphoria, and becoming reinforcing.
Finally, when alcohol affects a different receptor system (GABA system) in the brain, these GABA-related neurons release dopamine into the reward system. The GABA system is also involved in creating the depressant effects of alcohol.
It is believed that dopamine is involved in reward, wanting, craving, learning, but it is not directly involved in the euphoria. But the pleasurable feelings (euphoria) that is gained from using drugs is mediated by another system, called the endorphin system. Endorphins are opiate-like molecules (like heroin, morphine and Oxycontin), but are created in small quantities in the brain of humans and animals. It is likely that the euphoria that one gets from using drugs and alcohol is mediated by this endorphin system.
If you or a family member is struggling with cravings and addiction, and is suffering from the consequences of drug and alcohol use, the staff at the National Addiction Institute can assist you in locating the proper, life-saving resources that can help you change your life. You can call us at 844-889-8140, or contact NAI online, confidentially.