Dopamine Drives Early Addiction to Heroin: A Review and Commentary
This paper is discussing the driving force behind positive reinforcement in heroin addiction. Up until recently researchers haven’t nailed down the role that dopamine plays in addiction. The onset of addiction is caused by drug reinforcement which is essentially a reward in your brain when using drugs such as heroin. The purpose of this study was to gain a better understanding of what centers of the brain have input on drug reinforcement. By doing this, researches would be able to better understand addiction and how to alleviate it as well as understand the mechanisms of opioids and their highly addictive personalities.
To begin their study, the team used a fluorescent sensor to measure the levels of dopamine in a center of the brain called the nucleus accumbens, in mice. The nucleus accumbens is known to be a primary site of reward behavior. Researchers found that after a minute of giving the mice heroin, there was a significant spike in dopamine levels, as shown by the fluorescent sensor.
The activity of the dopamine neurons was measures by the activity of calcium, which is a very important factor in action potentials of neurons. Action potentials are how neurons communicate with other neurons and different parts of the body. The dopamine neurons were activated after repeated administration of heroin, which was synonymous with the findings of the previous test.
To further prove their findings, the researchers silenced dopamine neurons in rats that had already developed addictions to heroin. The mice with already establish addictions had access to a lever that allowed them to self-administer heroin. When researchers silenced the dopamine neurons in the mice, they found that the mice were less likely to self-administer the drug. When they used this same technique earlier in the addiction phase the mice were much less likely to develop the self-administering habit.
A final test that researchers did used mice that had been genetically changed so that their dopamine neurons were activated by light, which rats were able to self-stimulate, again by using a lever. Their purpose was to see if heroin would replace the reinforcing behavior effect from the light. Like the other tests researchers did, the results of this were similar. Mice that were given heroin were much less likely to use the lever to self-administer light than the mice that only had access to light. The results of this support the claim that the reinforcing effects of heroin are concerned with dopamine.
This paper was especially interesting to me because there’s so much relevance to it. There is an opioid epidemic in our country; often the addictions start with opioid prescriptions from doctors when a person suffers physical trauma. These findings could help researchers find ways to create new pharmaceuticals that elicit the same effects that opioids do, but maybe act on different neurotransmitters or receptors to reduce the addictive qualities that opioids have. It also gives more insight to addiction treatments and therapies because we have more knowledge on what parts of the brain are being targeted by repeated drug use.
I love learning about this kind of stuff and I hope that more and more literature comes out so that we can further our knowledge on how to combat drug addiction and hopefully drug use as well.