Von Frey Test for Mechanical Allodynia

The mechanical allodynia induced by oxaliplatin was assessed by Von Frey hair test before the first administration of drugs (on day 0) and on days 7, 14, 22, and 25. The rats were placed in a clear plastic box (20 cm × 17 cm × 13 cm) with a wire mesh floor and allowed acclimatization for 30 min prior to testing. Von Frey filaments (Stoelting, Wood Dale, IL, United States) ranging from 1 to 26 g bending force were applied to stimulate the mid-plantar skin of each hind paw at 3–4 s intervals. The minimal pressure level [in gram (g)] that initiated a withdrawal response was recorded. A positive response was noted if the tested paw was withdrawn sharply during 5 of the 10 trials.