Figure 1

Acute thermal and mechanical pain and chemical-induced pain in p2rx4^-/- mice. (A) Tail-flick and (B) paw-flick tests. Values represent the latency (sec) for animals to flick their tail or paw away from the heat source (wild-type, n = 5; p2rx4^-/-, n = 4). (C) Mechanical pain test. Values indicate the threshold (g) to elicit paw withdrawal behavior in response to mechanical stimuli (wild-type, n = 5; p2rx4^-/-, n = 4). (D) Visceral pain in response to acetic acid (0.8%). Values represent the numbers of abdominal stretches (writhes) (wild-type, n = 6; p2rx4^-/-, n = 5). (E) Formalin test. Mice were injected intraplantarly with formalin (5%, 20 μL). Values represent the duration (sec) of licking and biting responses for each 5-min interval (E), from 0 to 5 min (1st phase) and for 10–60 min (2nd phase) (inset) (wild-type, n = 8; p2rx4^-/-, n = 6). All data are presented as means ± SEM.