A glutamatergic Sp5C-STN circuit mediates chronic migraine in mice.

Chronic migraine (CM) is a prevalent and highly debilitating neurological disorder. Functional magnetic resonance imaging (fMRI) studies have demonstrated associations between abnormal brain region activation and CM, yet the underlying complex neural circuitry mechanisms remain unclear. The spinal trigeminal nucleus caudalis (Sp5C) serves as the primary central hub for orofacial nociceptive input, receiving trigeminal pain signals and projecting to higher-order centers such as the thalamus. Therefore, we sought to investigate whether the Sp5C region and its associated circuits were involved in CM pathogenesis. In this study, we established a CM mouse model through repeated intraperitoneal injections of nitroglycerin (NTG). Using a combination of <i>in vivo</i> fiber photometry and <i>in vitro</i> c-Fos immunohistochemistry, we found a marked periorbital and plantar mechanical allodynia in CM mice, accompanied by increased glutamatergic neuronal activity in Sp5C. Chemogenetic manipulation of Sp5C glutamatergic neurons (Sp5C^Vglut2) bidirectionally modulated migraine-like behaviors and induced pain-related affective states, as evidenced by conditioned place preference/aversion (CPP/CPA) paradigms. Anterograde viral tracing revealed dense projections from Sp5C^Vglut2 to the subthalamic nucleus (STN), which was activated in CM mice. Optogenetic activation of the Sp5C-STN pathway similarly produced migraine-like behaviors and pain-related aversive memory in mice. Altogether, we revealed a critical role of the Sp5C^Vglut2-STN circuit in the development and modulation of CM. Our findings provide novel mechanistic insights into the central mechanisms underlying CM, establishing potential theoretical foundations for clinical diagnosis and therapeutic development.