Spontaneous pain-associated facial expression and efficacy of clinically used drugs in the reserpine-induced rat model of fibromyalgia.

Spontaneous pain-associated facial expression and efficacy of clinically used drugs in the reserpine-induced rat model of fibromyalgia. Eur J Pharmacol. 2019 Oct 04;:172716 Authors: Nagakura Y, Miwa M, Yoshida M, Miura R, Tanei S, Tsuji M, Takeda H Abstract Fibromyalgia-associated chronic pain occurring without organic causes exerts negative effects on patients' quality of life, thereby necessitating the development of superior drugs. Since non-organic pain in patients with fibromyalgia occurs without external stimuli, an endpoint measure that reflects patients' spontaneous pain should be implemented in preclinical research. The present study is the first to apply the rat grimace scale (RGS), a facial expression-dependent measure developed for quantifying spontaneous pain, to the rat with reserpine-induced myalgia, an animal model of fibromyalgia exhibiting non-organic pain. Animals were videotaped and still images of facial expressions were captured and scored in a blind fashion. The reserpine-induced myalgia rats exhibited a significant increase in the RGS score, which was sustained for 2 weeks or more after the induction of fibromyalgia-like state by reserpine injection. The period of RGS score elevation was similar to that of reduced paw withdrawal threshold (PWT) measured using the von Frey filament test, a conventional measure of evoked pain. The elevated RGS score and the decreased PWT were relieved by gabapentin (an α2δ sub...
Source: European Journal of Pharmacology - Category: Drugs & Pharmacology Authors: Tags: Eur J Pharmacol Source Type: research