DRD4/DAT1 mRNA expression in attention deficit hyperactivity disorder children before and after methylphenidate treatment / 中华行为医学与脑科学杂志

ABSTRACT

Objective To investigate mRNA expression level changes of dopamine transporter gene (DAT1) and dopamine receptor gene(DRD4) in attention deficit hyperactivity disorder(ADHD) children's peripheral blood before and after methylphenidate treatment,and to explore associations between the mRNA expression level and symptom severity,as well as methylphenidate response.Methods Forty five ADHD children by DSM-Ⅳ diagnostic criteria,aged six to fifteen years old participated in a six-week drug titration treatment of metbylphenidate.ADHD-RS-Ⅳ Home Version, WCST and VCPT were used to evaluate the ADHD clinical symptoms and cognitive functions.RNA Simple Total RNA Kit was used to extract the total RNA.After reverse transcription, the obtained c-DNA was used in the following qRT-PCR to evaluate relative mRNA expression of the candidate genges before and after medication.Results The DRD4 mRNA relative expression level after taking methylphenidate was significantly higher than that before methylphenidate treatment (0.23 ± 0.23 vs 0.16± 0.18, P =0.041).There was no significant difference between DAT1 mRNA relative expression level before (0.43 ± 0.40) and after (0.43±0.40) methylphenidate treatment.No significant difference was found on eitber basal DAT1/DRD4 mRNA expression or fold change of DAT1/DRD4 mRNA expression before and after medication between methylphenidate treatment responders and non-responders groups.There was a positively significant correlation between baseline DRD4 mRNA relative expression level and erroneous T score of CPT(r=0.424, P=0.025) , however, no other statistically significant correlation was found between basal DRD4 mRNA relative expression level and ADHD-RS-Ⅳ total score,WCST conceptual level, CPT missing T score, and CPT reaction T sco~ (all P＞0.05).There was also no statistical significant correlation between basal DAT1 mRNA relative expression level and ADHD-RS-Ⅳ total score,WCST conceptual level,and CPT T scores(all P＞0.05).Conclusion DRD4 gene function may be increased after methylphenidate treatment and play an important role in impulsivity behavior of ADHD.Therefore, DRD4 mRNA expression level might be a biomarker for ADHD diagnosis and a predicting indicator of drug efficacy.