Positron Emission Tomographic Measure of Brain Dopamine Dependence to Nicotine as a Model of Drugs of Abuse

Chapter 8:
Nicotine enhances the amount of dopamine in the brain, thus making the drug very addictive. The researchers in the present study knew that using nicotine for a long or even short amount of time will increase the tyrosine hydroxylase (TH) in the ventral tegmental area and locus coeruleus in monkeys. In humans, more dopamine is increased by nicotine in the putamen and caudate than in nonsmokers. This study is trying to "support the hypothesis that overnight abstinence after short-term daily nicotine treatment in conscious monkeys reduces striatal DA (dopamine) utilization." Even though the researchers tested on monkeys, the technique applied to the study may also be used on human smokers.
Eight male monkeys were used. They were given L-DOPA for radioactivity. In the acute nicotine study (or short term) and the repeated nicotine study, the monkeys were measured by the positron emission tomography (PET) for 64 minutes. To compare high and low nicotine condtions a paired samples t-test was performed. Researchers were mainly interested in the cerebellum and striatum. After overnight nicotine abstinence, the brain said it was addicted to nicotine. Researchers looked at the white matter and occipital areas of the brain as control levels, becuase L-DOPA was not present there.
After the final analysis, researchers concluded that L-DOPA did help quantify dopamine in dependent smokers. They stated their methods could be used for all abused drugs that emit serotonin or CA (or brain catecholamines).
Through PET scans, the research can be used to locate where the drugs affect the brain. Even in the absence of nicotine, the brain "said" that it was addicted to the substance. This demonstrates how easily the brain is addicted to stubstances due to the presence of these false neurotransmitters (i.e. nicotine).
Domino, E.F, Tsukada, H., Harada, N. (2009). Positron emission tomographic measure of brain dopamine dependence to nicotine as a model of drugs of abuse. Psychopharmocology, 204, 149-153. Accessed by EbscoHost. doi: 10.1007/s00213-008-1445-8

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