Dorsal hypothalamic dopaminergic neurons play an inhibitory role in the hypothalamic‐pituitary‐adrenal axis via activation of D2R in mice

Abstract Aim The present study investigated the effects of dorsal hypothalamic dopamine (dh‐DA) neurons on activation of hypothalamic‐pituitary‐adrenal (HPA) axis in adult male mice. Methods Tyrosine hydroxylase‐labelled DA neurons, DA content, c‐Fos immune‐positive (c‐Fos+) cells and CRH expression in paraventricular nuclei (PVN), serum CORT and ACTH were examined at 4‐, 8‐, and 12‐hour after a signal injection of MPTP (20 mg kg −1 ) respectively. Results The dh‐DA neurons and DA content in PVN at 4‐hour post‐MPTP were reduced with recovery at 12‐hour post‐MPTP, while decline of nigrostriatal DA neurons and DA content in striatum started from 12‐hour post‐MPTP. Number of c‐Fos+ cells, and CORT/ACTH levels increased at 4‐hour post‐MPTP, followed by recovery at 12‐hour post‐MPTP. The CRH mRNA was elevated at 4‐hour post‐MPTP, and sustained for over 12 hours. At 2‐hour post‐MPTP, PVN‐injection of D2R agonist quinpirole corrected the increases in c‐Fos+ cells, CORT/ACTH and CRH mRNA, but D1R agonist SKF38393 did not. PVN‐injection of D2R antagonist L‐sulpiride alone caused increases in c‐Fos+ cells, CORT/ACTH and CRH mRNA. Similarly, PVN‐injection of CB1R agonist WIN552,12 prevented the increases in c‐Fos+ cells and CORT/ACTH rather than CRH mRNA, which were blocked by CB1R antagonist AM251. Levels of PKA and CREB phosphorylation in PVN were increased at 4‐hour post‐MPTP, which were blocked by quinpirole, but not WIN552,12. PKA inhibitor H89 corrected the increase of CRH mRNA at 8‐hour post‐MPTP. Conclusion The activation of dh‐DA neurons regulates negatively HPA axis through targeting D2Rs of CRH neurons to enhance endocannabinoid release and inhibit PKA‐CREB pathway.