D4 and D5 dopamine receptor mRNA expression in human peripheral blood lymphocytes among cooccurring opioid and amphetamine-type stimulants use disorder undergoing methadone maintenance therapy

Abstract

Introduction: Opioid and amphetamine type stimulant (ATS) exert their rewarding effects by stimulating the dopaminergic system in the mesolimbic area. It has been suggested that dopamine system in peripheral blood lymphocytes reflect the central dopamine system’s activity and pathology, especially in neuropsychiatric diseases including drug addiction. The present study aimed to assess the effect of co-occurring opioid and ATS (COATS) addiction towards mRNA expression of dopamine receptors DRD4 and DRD5 in peripheral blood lymphocytes (PBLs) of drug dependent subjects (n=36) undergoing methadone maintenance therapy in comparison to control subjects (n=36). Materials and methods: Ten mL blood were obtained from the subjects followed by lymphocyte isolation, RNA extraction and reverse transcription. DRD4 and DRD5 mRNA expression in peripheral lymphocytes was assessed using real-time PCR. The DRD4 mRNA expression but not DRD5 was significantly reduced in the peripheral lymphocytes of COATS subjects. Results: Mean expression value for DRD4 was 14.0+0.24 among patients and 13.3+0.25 among control subjects. For DRD5 it was 12.87 + 0.75 among patients and 12.59 + 1.24 among controls. Conclusion: Inconclusion, co-occurring opioid and ATS addiction was associated with persistent deficiency of DRD4 but not DRD5 in PBLs.