Expanding Our Knowledge of Dopamine Pathways to Help Treat Addiction

There are two theories when it comes to addiction. One is the physical dependence model, which can be explained by tolerance leading to painful or unpleasant withdrawal symptoms.  Another belief is the positive reinforcement model. This states that a person will continue engaging in a certain behavior or activity because they are addicted to the pleasure that it brings them. We know that addiction is correlated with a reward system in the brain. This system is controlled by the neurotransmitter dopamine (DA) via the mesolimbic pathway. The mesolimbic DA pathway is activated anytime you engage in activities that the brain deems pleasurable. These activities can include drug use, eating certain kinds of food, gambling and many others.                                                       

Understanding precisely how the dopamine reward system works is important for many reasons. If we know the pathway of mesolimbic DA, we can use this knowledge to control DA release and signaling to help treat people with addiction. I recently attended a seminar given by Dr. Stephen Steidl in which he discussed his use of optogenetics (using light to control cells that have been genetically modified to activate in the presence of light) in rats to measure the regulation of mesolimbic DA signaling. His results reinforced previous reports that laterodorsal tegmental nuclei (LDTg) inputs to the ventral tegmental area (VTA) in reward. There were however some inconsistencies with previous studies that they pointed out. Most notably, Dr. Steidl’s findings showed that “(1) driving LDTg input s to the VTA increases dopamine overflow in the nucleus accumbens and (2) activation of D1 and D2 DA receptors is necessary for the reinforcing effects of optogenetic intracranial self-stimulation of LDTg inputs of the VTA.” Dr. Steidl’s findings are key to increasing our knowledge of the mesolimbIc pathway so that we can help people who have abnormalities within the dopamine reward system and are struggling with addiction.

Studies on correcting abnormalities of the mesolimbic pathway in humans are already being done. There was a recent article that discussed transcranial magnetic stimulation (TMS) and how it could be useful in treating people with addiction. TMS is a non-invasive procedure that uses magnets to stimulate neurons. Luigi Gallimberti, an Italian doctor and his partner, neurocognitive psychologist Alberto Terraneo teamed with the National Institute of Drug Abuse and University of California, San Francisco in an experiment using TMS on people with drug addictions. Their results showed that 11 out of the 16 people treated with brain stimulation ended up being drug free, while only 3 out of the 11 who were treated with standard care (medication, psychiatry, etc.) came out drug free. Addiction is an extremely difficult disease to treat, and I think that the results of this experiment gives hope to the future of addiction treatment.

Works Cited

Steidl, S., Wang, H., Ordonez, M., Zhang, S., & Morales, M. (2016). Optogenetic excitation in

            the ventral tegmental area of glutamergic or cholinergic inputs from the

            laterdorsal tegmental area drives reward. European Journal of

Neuroscience, 45(4), 559-571. doi:10.1111/ejn.13436

National Geographic Magazine (2017, September). How Science is Unlocking Secrets of Addiction

            Retrieved October 17, 2017 from: http://www.nationalgeographic.com/magazine/2017/09/the-addicted-brain/