Glucocorticoids/glucocorticoid receptors effect on dopaminergic neurotransmitters in ADHD rats

Dexamethaone (DEX, glucocorticoid receptor agonist) and RU486 (glucocorticoid receptor inhibitor) may affect the behavior of attention deficit hyperactivity disorder (ADHD) rats, by changing the level of dopamine and noradrenaline and dopamine transporter in different regions of their brain. In this study, we have investigated the effect and the underlying mechanism of Glucocorticoids/Glucocorticoid receptors on dopaminergic neurotransmitters in ADHD Rats. Thirty male Wistar Kyoto rats (WKY) and 30 male spontaneously hypertensive rats (SHR) were respectively divided into 3 groups randomly as follows: a GR agonist group (DEX), a GR inhibitor group (RU486) and a control group (CON). Open field test and Y maze were performed respectively to assess the behavior of the rats. The levels of dopamine, norepinephrine, and dopamine transporter (DAT) in the prefrontal cortex and striatum were also tested. Our results showed that, the behavior of rats were improved after DEX treatment. We also found that the level of DA and NE increased in DEX group, but decreased significantly in RU486 group. Immunohistochemical assay showed that DAT expression level in DEX group was significantly less than that in RU486 and CON group. In conclusion, by regulation of glucocorticoid receptor, GR agonist can decrease DAT expression, resulting in the increase of DA and NE levels in brain that ameliorate hyperactivity and attention deficit in ADHD rats. Our results suggest that the effects of glucocorticoid receptor on dopaminergic neurotransmitter in the central nervous system may be involved in the pathogenesis of ADHD.