Effects of Mirogabalin on Hyperalgesia and Chronic Ocular Pain in Tear-Deficient Dry-Eye Rats

PURPOSE. Patients with dry eye disease (DED) sometimes complain of ocular pain. DED-related ocular pain has many similarities with neuropathic pain. Mirogabalin, a novel ligand for the & alpha;28 subunit of voltage-gated calcium channels, is approved for treat-ing neuropathic pain in Japan. This study aimed to investigate the effect of mirogabalin on hyperalgesia and chronic ocular pain in a rat DED model. METHODS. DED was induced in female Sprague Dawley rats by unilaterally excising the external lacrimal gland (ELG) and Harderian gland (HG). After 4 weeks of ELG and HG removal, tear production (pH threads) and corneal epithelial damage (fluorescein stain-ing) were evaluated. Corneal hyperalgesia and chronic pain were analyzed, respectively, by measuring capsaicin-induced eye-wiping behavior and c-Fos expression in the trigem-inal nucleus. Mirogabalin (10 or 3 mg/kg) was evaluated for effects on DED-induced hyperalgesia and chronic ocular pain. RESULTS. Tear production was significantly lower in DED-induced eyes than in control eyes. Corneal damage was significantly higher in DED eyes than in control eyes. Hyper-algesia and chronic ocular pain were detected 4 weeks after ELG and HG removal. Five days of mirogabalin administration significantly suppressed capsaicin-induced eye -wiping behavior, which indicated the suppression of ocular hyperalgesia. Administration of 10 mg/kg mirogabalin significantly reduced c-Fos expression in the trigeminal nucleus, which indicated the amelioration of chronic ocular pain. CONCLUSIONS. Mirogabalin suppressed DED-induced hyperalgesia and chronic ocular pain in a rat DED model. Our findings suggested that mirogabalin might effectively alleviate chronic ocular pain in patients with DED.