Models & Assays
Formalin Test
The formalin test has both an inflammatory and neuropathic pain component and thus serves as a useful initial screening test. Intra-plantar injection of formalin produces a biphasic incidence of licking the injected area, with an early (i.e. 0-10min) phase due to direct activation of TRPA1 channels localized on sensory neurons, and a late (10-60min) phase which is believed to reflect both central sensitization and local inflammatory response to formalin-induced TRPA1 channel activation and local tissue damage.