Neurotransmitter system aberrations in patients with drug addiction

Drug dependence may affect the neurotransmitter system levels in the human body. This study recruited 113 healthy control subjects, 118 heroin-dependent patients and 118 methamphetamine-dependent patients and examined the serum 5-HT, dopamine, glutamate and norepinephrine levels in the 349 volunteers. ELISA assays demonstrated that the serum 5-HT levels were significantly reduced in the drug-dependent patients, whereas the serum dopamine and glutamate levels were both significantly increased in the drug-dependent patients when compared with control subjects. In contrast, the norepinephrine levels did not exhibit a significant difference between the drug-dependent and control subjects. We also used qRT-PCR to analyze the transcriptional expression levels of 5-HT_1A, 5-HT_1B, dopmaine-D1 and dopamine-D2 receptors in the blood of drug-dependent patients and controls, and the results show that only 5-HT_1B receptor levels were dysfunctional in the heroin abusers. In addition, our results suggest that serum 5-HT, dopamine, and glutamate levels had the potential to differ between drug abusers and controls, and combining those three potential biomarkers provided an accurate means to differentiate between the drug-dependent and control subjects. Taken together, our study reveals a differential profile of neurotransmitters in the heroin-dependent patients and methamphetamine-dependent patients, and this revelation may contribute to understanding the pathophysiology of drug addiction.