Have you ever heard someone say, “S/he has an addictive personality, so don’t do X”? It seems as though some people are more likely to become addicted to something than others. Much of the variation in our behaviors, personalities, and the diseases we get, arise from the way our genes are read, and not necessarily what our genes are. DNA is the blueprint for our life. If you imagine that a team of contractors has a blueprint with cross-outs over certain places and highlights over others, the highlighted parts will be read more carefully, while the parts that have been crossed out will be ignored. Certain proteins do this to our DNA; some parts get read, while others are silenced, and this deciding factor is based on environmental factors (e.g., sleep, exercise, diet, stress). This is why people can have similar DNA, but don’t act, look, or think the same. When parts of our DNA get read, our cells can make more proteins that each have specific consequences on our behavior.
Some rats get more excited at shiny new things than others. Putting rats in a new cage and measuring how much they explored, allowed researchers to breed the eager rats with each other, resulting in a genetic line of them. Through testing, they realized that not only were these rats more likely to self-administer cocaine than others, but they also developed traits that resembled addiction in humans such as looking for the drug when it was not available. These rats seemed to display and “addictive personality”. They had made an animal model for addiction, which could be used to answer crucial questions about addiction in humans.
What’s useful about animal models is that you can dissect their brains to measure the amount of neurotransmitter around, unlike with humans. Neurotransmitters are tiny molecules that carry messages from one cell to another, and that message can only be received at specific receptors. After researchers measured the levels of these proteins in rat brains, it was clear that the genetically anxious rats had lower levels of the receptor that responds to the motivation neurotransmitter, called dopamine, compared to their less excitable rat brethren. This type of rat has less dopamine receptors because a certain protein crosses out the part of its DNA blueprint that calls for the receptor to be made. This overwhelms the system with dopamine, which identifies that excess dopamine is one of the culprits for that susceptibility to cocaine addiction.
Thankfully, there are multiple developments in gene therapy that would potentially be able to help those with too much dopamine. Scientists can try to force the synthesis of more receptors, or they can find a way to decrease the level of dopamine itself. Either of these might reverse these addictive behaviors. So even though people can inherit a blueprint that gave them addictive personalities, there is ample hope that their blueprint could be modified to ensure the individual has a life without struggling with addiction.
Ennis, C. (2014, June 20). Epigenetics 101 – part 2: cancer, chaos and chemo | Cath Ennis. Retrieved October 15, 2017, from https://www.theguardian.com/science/occams-corner/2014/jun/20/epigenetics-cancer-chaos-chemotherapy
Flagel, S. B., Chaudhury, S., Waselus, M., Kelly, R., Sewani, S., Clinton, S. M., . . . Akil, H. (2016). Genetic background and epigenetic modifications in the core of the nucleus accumbens predict addiction-like behavior in a rat model. Proceedings of the National Academy of Sciences, 113(20). doi:10.1073/pnas.1520491113