FM1-43 inhibits behavioural responses to noxious mechanical stimuli. (A) 5 nMoles FM1-43 (P < 0.05, n = 7, average increase above pre-injection control 200.7 ± 76.6%) and FM3-25 (P < 0.05, n = 3, 80.9 ± 11.6%) both increased the 50% withdrawal threshold in the von Frey test. Injection of the vehicle had no significant effect. (B) Using the mouse tail to test FM1-43 in the Randall-Selitto assay it was found that FM1-43 increased pain thresholds by 55.2 ± 23.9 % (2 × 20 nMoles top and bottom of tail injected, n = 6, Student's unpaired t-test versus vehicle effect, P < 0.05) whilst vehicle injection had no significant effect on thresholds (n = 6). Injection of the 5% DMSO vehicle (n = 9) had no significant effect.