Gonadotropin-releasing hormone alleviates chronic pain-related depression in male mice by rebalancing the anterior cingulate cortex excitatory-inhibitory processes via the protein kinase C/Erb-B2 receptor tyrosine kinase 4 pathway.

Depression is a common comorbidity of chronic pain. Gonadotropin-releasing hormone (GnRH) and its receptor (GnRHR) expressed in the central nervous system are involved in non-reproductive functions. Herein, we aimed to elucidate the role and mechanism of action of GnRH in pain-related depression like behaviour in a mouse model. And we found that both GnRH and GnRHR were down-regulated in the anterior cingulate cortex of mice that were subjected to chronic pain-induced depression with complete Freund's adjuvant. Specifically, either systemic treatment with GnRH agonists or GnRH overexpression in the anterior cingulate cortex effectively ameliorated the chronic pain-induced depression-like behaviour via GnRHR signalling. Moreover, GnRHR co-localized with both excitatory and inhibitory neurons, and GnRH agonists or overexpressed GnRH rescued the complete Freund's adjuvant-stimulated imbalance of excitatory-inhibitory neurons in the anterior cingulate cortex. Chemogenetic activation of anterior cingulate cortex neurons reversed GnRH agonist-induced improvement in depression-like behaviour in complete Freund's adjuvant-treated mice. Furthermore, this specific role of GnRH was dependent on the activation of protein kinase C and Erb-B2 receptor tyrosine kinase 4 signalling pathway. Therefore, our findings indicate that GnRH/GnRHR is involved in the development of chronic pain-related depression, which may through rebalancing the excitatory-inhibitory neurons via the activation of protein kinase C/Erb-B2 receptor tyrosine kinase 4 pathway. Thus, GnRH could be a potential target for the treatment of chronic pain-related depression.