Before Dr. Hoffman's presentation, I had the impression of alcohol addiction as an issue regarding cravings, behavior, and complications in controlling alcohol consumption. Although I did have an understanding that addiction has a significant effect on the brain, I did not take into account how specific receptors involved in communication between neurons could also be a factor in drinking behavior. Dr. Hoffman's research made me perceive that alcohol use disorder isn't only about an individual's choice. More specifically, it involves biological differences that could help explain why continuously drinking alcohol can be an incredibly difficult task to quit.
One aspect of Dr. Hoffman's research that caught my attention was her investigation of AMPA receptors. These receptors respond to glutamate, an excitatory neurotransmitter that helps neurons communicate with each other. AMPA receptors play a role within memory, learning, and changes in the strength of connections between neurons. This happened due to alcohol affecting these signaling pathways; researchers are intrigued to unveil whether targeting particular AMPA receptors could gear towards the solution of reducing excessive drinking,
Within Dr. Hoffman's research paper, she and her colleagues investigated a compound called JNJ-55511118, which inhibits AMPA receptors associated with a regulatory protein called TARP y-8. They examined whether this compound could diminish alcohol self-administration in mice. The researcher discovered that the treatment drastically reduced alcohol-reinforced responding within male mice; however, they did not reduce the response for a sucrose-only reward. In comparison, the same treatment did not produce the same outcome in female mice. This difference truly amazed me, since it suggests that a treatment targeting precise brain mechanisms may potentially not work as effectively in every biological group.
Siddiqi et al. (2023) penned a research article titled “Prefrontal cortex glutamatergic adaptation in a mouse model of alcohol use disorder” that grabbed my attention regarding this topic. Some researchers at institutions such as The Scripps Research Institute and Binghamton University conducted this study. The researchers analyzed how excessive alcohol exposure and withdrawal substantially affected AMPA receptor function in the medial prefrontal cortex of male mice.
The prefrontal cortex is known as the executive control center, which is involved in behavioral control, decision-making, impulse control, and focus. Using a mouse model of alcohol dependence, the researchers observed increased AMPA receptor-mediated excitatory signaling in the prefrontal cortex. Furthermore, they also recognized reduced expression of specific genes that were associated with AMPA receptor subunits and synaptic plasticity during withdrawal. This indicates that alcohol dependence can alter neuronal communication in complex ways, even when few molecular measurements point in the opposite direction.
What caught my attention was the distinction between the two studies. Dr. Hoffman's research studies whether selectively inhibiting specific AMPA receptors could lower alcohol-seeking behavior. Whereas Siddiqi and colleagues assessed how being dependent on alcohol alters AMPA receptor function. The outside article was remarkably intriguing because AMPA receptor-mediated signaling decreased even though certain receptor-related genes decreased. When I first read these findings, I felt slightly confused. However, these outcomes suggest that changes in gene expression do not necessarily reflect how intensely receptors function. Both of the studies show why comprehending addiction needs examining both routes: functional and molecular changes that occur within the brain.
These conclusions could help researchers to develop refined treatments for alcohol use disorder. Knowing and understanding how alcohol changes AMPA receptor activity can result in treatments that account for variation in sex and drinking history. However, this may make it difficult to determine whether these findings apply to humans. Since Dr. Hoffman's study discovered various responses in female and male mice, further research may reveal whether sex also has an effect in how the brain responds to alcohol and addiction treatments.
Overall, Dr. Hoffman's presentation gave me insight about alcohol addiction from a biological standpoint. In addition, the outside article reinforced that insight by demonstrating how chronic alcohol exposure can modify AMPA receptor signaling in a brain region participating in behavioral control. These results raise a question for me about whether a better understanding of how alcohol changes AMPA receptors results in treatments that are more beneficial for different categories of people.
References
Hoffman, J. L., Faccidomo, S., Saunders, B. L., Taylor, S. M., Kim, M., & Hodge, C. W. (2021). Inhibition of AMPA receptors (AMPARs) containing transmembrane AMPAR regulatory protein γ‐8 with JNJ‐55511118 shows preclinical efficacy in reducing chronic repetitive alcohol self‐administration. Alcoholism: Clinical and Experimental Research, 45(7), 1424–1435. https://doi.org/10.1111/acer.14639
Siddiqi, M. T., Podder, D., Pahng, A. R., Athanason, A. C., Nadav, T., Cates-Gatto, C., Kreifeldt, M., Contet, C., Roberts, A. J., Edwards, S., Roberto, M., & Varodayan, F. P. (2023). Prefrontal cortex glutamatergic adaptations in a mouse model of alcohol use disorder. Addiction Neuroscience, 9, 100137. https://doi.org/10.1016/j.addicn.2023.100137
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