Transcutaneous occipital nerve stimulation alleviated migraine related pain by regulating synaptic plasticity and CGRP expression in the periaqueductal gray of male rats.

BACKGROUND: Clinical observations have shown that transcutaneous occipital nerve stimulation (tONS) is effective in treating migraine. However, the underlying mechanisms are poorly understood. This study employs a rodent model to investigate the therapeutic effects of tONS on migraine-related pain and to explore potential mechanisms. METHODS: The SD rats were used to establish the migraine model by repeated epidural infusions of inflammatory soup (IS). Modified bilateral electrodes were attached noninvasively for tONS treatments. Periorbital mechanical thresholds were assessed using von-Frey filaments, and other pain-related nociceptive behaviors were analyzed through video recordings. The expressions of c-Fos, synaptophysin (Syp) and calcitonin gene-related peptide (CGRP) in the trigeminal nucleus caudalis (TNC) and/or periaqueductal gray (PAG) area were measured by immunofluorescence and western blotting analyses. The excitatory synaptic transmission in the PAG was detected by whole-cell patch-clamp recording among migraine rats. RESULTS: The reduction in periorbital mechanical thresholds induced by repeated IS infusions was partially reversed by tONS treatments in migraine rats. Other pain-related behaviors, including exploration, rest, and unilateral grooming, consistently improved following tONS treatment. The TNC and PAG area were activated after IS modeling, and the CGRP expressions in the PAG significantly decreased after tONS treatments. tONS could inhibit the enhanced excitatory synaptic transmission in the PAG of migraine rats. CONCLUSIONS: Our findings suggest that tONS has therapeutic potential in treating migraine, with the PAG excitability and CGRP expression playing a role in its mechanisms of action. tONS may represent a promising non-invasive neuromodulation approach for the management of migraine in the future.