Anxiolytic-like effects of mirogabalin, a novel ligand for α 2 δ ligand of voltage-gated calcium channels, in rats repeatedly injected with acidic saline intramuscularly, as an experimental model of fibromyalgia

Mental disorders including anxiety and depression are common comorbidities in fibromyalgia patients, and exert a profound impact on their quality of life. Mirogabalin, a novel ligand for the α δ-subunit of voltage-gated calcium channels, shows analgesic effects in fibromyalgia and neuropathic pain models. To provide additional information regarding its potential utility for treating chronic pain, we examined its anxiolytic-like effects in rats repeatedly injected with acidic saline intramuscularly (Sluka model), as an experimental fibromyalgia model. Male Sprague-Dawley rats received two intramuscular injections of acidic saline (pH 4.0) into the gastrocnemius muscle. After the development of tactile allodynia demonstrated by decreased paw withdrawal threshold to von Frey filaments, anxiety-like behaviours were evaluated using the open field test and the elevated plus maze test. Sluka model rats exhibited anxiety-like behaviours in the open field test (significant decreases in distance travelled and time spent in the central area, and significant increases in time spent in the wall area) and the elevated plus maze test (significant decreases in time spent in the open arms and significant increases in time spent in the closed arms). A single oral dose of mirogabalin (3 or 10 mg/kg) significantly alleviated and normalised these anxiety-like behaviours. Sluka model rats exhibited anxiety-like behaviours in the open field test and the elevated plus maze test, but mirogabalin alleviated these behaviours. Mirogabalin might thus have the potential to relieve anxiety in fibromyalgia patients.