Pain Related Behaviors are Blocked by PBN. A - Mechanical Hyperalgesia/Allodynia are Blocked by ROS Scavenger PBN. Responses to mechanical stimulation with two strengths of von Frey filaments are shown for rats at baseline and 4 h after k/c injection into the left (L) knee joint. Secondary mechanical allodynia is tested on the footpad with the weak 10 mN stimulus (upper bar chart), and secondary mechanical hyperalgesia is observed with the stronger 47 mN stimulus (lower bar chart). Percent paw withdrawal frequency (PWF) is significantly increased at 4 h after i.p. pre-treatment with saline (n = 4). The hypersensitive responses are blocked by the ROS scavenger, PBN, injected intraperitoneally 2 h before induction of the knee joint inflammation (n = 4). B - Hotplate Response is Blocked by ROS Scavenger PBN. Response times in seconds (s) are shown for the hotplate test at baseline and five hours after k/c induced left (L) knee joint arthritis (Arth) in rats pre-treated with saline (n = 4) or ROS scavenger, PBN (n = 4). The PBN pre-treatment administered i.p. 1 h prior to induction of arthritis prevented development of secondary thermal hyperalgesia observed in the saline treated group.