The before and after images of people battling methamphetamine (meth) addiction show the devastating physical signs of meth abuse: skin lesions, rotting teeth, accelerated aging, and extreme weight loss. 77% of people addicted to amphetamines also abuse alcohol, but the effects of this combination on health are unknown. ASPET members Amanda Blaker and Dr. Bryan Yamamoto report on the Journal of Neuroimmune Pharmacology that exposure to both alcohol and meth reduces levels of dopamine and serotonin in the brain, two neurotransmitters that control how nerve cells communicate with each other.
Dopamine and serotonin affect every part of the body, from our emotions to our motor skills. Serotonin is considered a natural mood stabilizer, and low levels of it are associated with depression. Dopamine is known as the “motivation molecule” because it makes us want to do the things we enjoy again and again. Although meth causes a surge of dopamine in the brain followed by euphoria, continued meth use destroys the brain pleasure centers making it impossible to feel pleasure. This is accompanied by symptoms seen in individuals who abuse alcohol, such as impaired memory and loss of motor coordination.
Many meth users are also alcoholics, but the effects of this combination on brain chemistry are unknown.
Scientists know that alcohol causes inflammation in the body by “breaking” the protective barrier that lines the gastrointestinal tract. This allows the components of gut bacteria to leak out of the intestines and go into circulation, where they can move throughout the body and cause systemic inflammation.
In this study, lab rats were given a choice between two bottles: One containing water, and one containing 10% ethanol. Over 28 days, the rats developed a preference for the ethanol bottle, and bacterial components were found in their serum, a sign that the protective barrier of the gastrointestinal tract was compromised. After 28 days of consuming ethanol, the rats were given meth injections once every 2 hours to simulate meth exposure in humans. Although the bacterial components that entered circulation as a result of ethanol exposure are normally too large to enter the brain, they were found in the brains of rats that received both meth and ethanol, an indication that the combination allowed compounds into the brain that would otherwise not be let in.
The combination of ethanol and meth caused significant reductions in dopamine and serotonin in the brain, which did not occur when the rats were exposed to ethanol alone. The study also showed that the more alcohol the rats consumed prior to meth exposure the greater the reductions were in brain dopamine and serotonin. The inflammation caused by ethanol could have worsened the toxic effects of meth because when the rats received an anti-inflammatory drug at the time of ethanol exposure, inflammation was reduced and there was no further decrease in serotonin or dopamine after meth exposure.
This study points to an important role of inflammation caused by alcohol consumption as a factor that worsens the effects of meth on brain chemistry. Therefore, attenuating systemic inflammation may be an effective treatment for mitigating the effects of combining both substances.
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