In the United States, overdoses have passed car crashes and gun violence to become the leading cause of death. Heroin and other opioids such as pain killers have taken hold of many lives across the nation. Addiction may begin from prescription pain killers or desire to take them, but induce users into a sense of tranquility and cause an abusive cycle. It is known that drugs like Heroin cause a wave of pleasure through the reward pathways in the brain. Users often end up chasing the high that they received the first time they took the drugs and their brain struggling to maintain its own endorphin levels after opioids create an imbalance in the natural equilibrium in the reward pathways in the brain. Opioids produce a surge of dopamine release in the brain which is modulated through the Ventral Tegmental Area. In "Opioid-induced Rewards, Locomotion, and Dopamine Activation: A Proposed Model for Control by Mesopontine and Rostromedial Tegmental Neurons", Dr. Steidl explains the Dopamine pathways that cause drug addiction and conditioned place preference behavior. The VTA has projections from the RMTg, LDTg, and the PPTg in particular that seem to contribute to the addictive behavior that comes from opioids. The New York Times spoke to individuals who had previously struggled with Heroin and other Opioids in the past and when asked to describe their addiction they stated "It’s like a time bomb. You’ve got 24 hours to get heroin, or you’re going to be really sick. You wake up, and your whole life is just based around it."(Sinha). These pathways of addiction are still being understood with research that demonstrates that opioids directly inhibit VTA GABA release, and because GABA is an inhibitory neurotransmitter, its inhibition results in an increase of dopamine release. Dr. Steidl's work demonstrates that Opioids are complex substances because they recruit multiple reward pathways in the brain and thus their euphoric effects can cause extreme withdrawal and dependence. Heroin dependence can cause individuals to act irrationally just to achieve that same level of happiness or reward. Individuals may commit crimes for money, betray family and friends, and have little regard for many of the things that their lives used to be centered around. Currently, the model that has been developed in Dr. Steidl's lab enforces that the RMTg, LDTg, and PPTg all work together in feedback loops promoting one another to send signals to the VTA in order to further release dopamine as a result of the effects of these opioids. These pathways have been studied in Dr. Steidl's work through the use of optogenetics, in which a virally transfected mouse has certain ion channels in the brain that can be inhibited or excited based on the wavelength of light that is shined on them. Dr. Steidl has looked at Acetylcholine and Glutamate channels mainly. Dr. Steidl has most recently found that VTA glutamatergic receptor mechanisms critically contribute to the development of sensitization to cocaine and morphine. Essentially, explaining that glutamate itself makes you more sensitive to the drug. Through experiments regarding drug cocaine, but utilizing similar reward pathways in the brain Dr. Steidl found that LDTg cholinergic inhibition ( turning off the Acetylcholine channels through optogenetics) resulted in less sensitization to the drug cocaine. These are recent results in his lab which have not been published yet but were explained during his presentation. These results mean that if it can be possible to induce this cholinergic inhibition, it would make individuals less likely to relapse and have less sensitization to the drug of abuse overall. Current healthcare solutions for the opioid epidemic can be effective, but with heroin and other drugs of abuse often impacting individuals from more disadvantaged backgrounds it can be difficult to repair the damage done to one's life and improve their outlook for the future. Doctors currently prescribe long-term use of medications, like buprenorphine, methadone and naltrexone. But only about 25 percent of outpatient centers provide them in the nation, so it is clear how there is much more that must be done in terms of discovery and effective treatment as many of these treatments do not work for individuals or take a long time to have an effect. With Dr. Steidl's work, there is a possibility of greater understanding of the pathways towards drug abuse and addiction and through this understanding, it can become easier to find and develop pharmaceuticals and treatment options that can help individuals who have struggled with addiction to fight the urge to relapse as well as those even currently struggling to lessen the rewarding effects and restore balance to the brain's reward pathways.
Works Cited
Sinha, Shreeya, et al. “Heroin Addiction Explained: How Opioids Hijack the Brain.” The New York Times, The New York Times, 19 Dec. 2018, www.nytimes.com/interactive/2018/us/addiction-heroin-opioids.html?rref=collection%2Fbyline%2Fshreeya-sinha.
Steidl, Stephan, et al. “Opioid-Induced Rewards, Locomotion, and Dopamine Activation: A Proposed Model for Control by Mesopontine and Rostromedial Tegmental Neurons.” Neuroscience & Biobehavioral Reviews, vol. 83, 2017, pp. 72–82., doi:10.1016/j.neubiorev.2017.09.022.
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