Animal experiment:

Rats[1]Male Sprague-Dawley rats (250-400 g) are used for all experiments and are housed in a temperature controlled room with a 12/12-hr day/night cycle. Food and water are available ad libitum. Spontaneous and evoked neuronal activity is then measured 5, 15, 25, and 35 min after systemic injection of A-967079 (30 μmol/kg, i.v.) or vehicle (polyethylene glycol). The intravenous injection of A-967079 or vehicle is completed over a 6-7 min period. The i.v. dose of A-967079 is selected based on extrapolated plasma levels that are effective in behavioral studies[1].

A-967079 is an antagonist of transient receptor potential A1 (TRPA1) receptor with IC50 values of 289 nM and 67 nM at rat and human TRPA1 receptors, respectively [1].

There is a larger family of transient receptor potential (TRP) ion channels. In this family, there are TRPV, TRPM, TRPC, TRPN, TRPP and TRPML. TRPA1 is a part of this family and is expressed in small and medium-sized peptidergic primary afferent sensory neurons that also express TRPV1 [1].

Treatment with A-967079 attenuated Ca2+ signal in WT TG neurons and resulted in a further reduction in Trpv4-/- TG neurons in response to formalin. Treatment with A-967079 reduced the percentage of responsive cells from 27.7% to 15.8% when acutely blocking TRPA1 and to a mere 3.2% in Trpv4-/- TG neurons plus TRPA1 inhibitor [2].

Spontaneous activity of WDR neurons can indicate central sensitization and possibly non-evoked or ongoing pain. In uninjured and CFA-inflamed rats, systemic injection of A-967079 at 30 μmol/kg, i.v. made responses of wide dynamic range (WDR) and nociceptive specific (NS) neurons decrease, following noxious pinch stimulation of the ipsilateral hind paw. Similarly in both OA and OA-sham rats, A-967079 decreased the responses of WDR neurons to high-intensity mechanical stimulation of the knee joint. Administration with A-967079 also reduced WDR neuronal responses to low-intensity mechanical stimulation (10 g von Frey hair) in CFA-inflamed rats, but not in uninjured rats. Additionally, A-967079 injection decreased the spontaneous activity of WDR neurons in CFA-inflamed rats, but not in uninjured, OA, and OA-sham animals [1].

References:
[1]. McGaraughty S, Chu KL, Perner RJ, et al. TRPA1 modulation of spontaneous and mechanically evoked firing of spinal neurons in uninjured, osteoarthritic, and inflamed rats. Molecular pain, 2010, 6(1): 1.
[2]. Chen Y, Kanju P, Fang Q, et al. TRPV4 is necessary for trigeminal irritant pain and functions as a cellular formalin receptor. PAIN, 2014, 155(12): 2662-2672.