Thermal hyperalgesia (plantar test)

Using the plantar test and infrared radiation from the plexiglass surface to the animal’s hind paw, heat hyperalgesia to the radiant heat stimulus was measured.

Paw withdrawal latency was expressed as the latency (sec) between the radiant stimulus start and paw withdrawal. Thermal stimulation was repeated three times with 5 to 10 min intervals. A cut-off time of 22 sec was used to avoided skin surface damage (27).