Measurement of mechanical allodynia
Mechanical allodynia was assessed by measuring rats’ paw withdrawal
threshold in response to probing with a series of fine calibrated
filaments (von Frey, Stoelting, Wood Dale, IL). Rats were placed in
suspended plastic cages with wire mesh floor, and each von Frey filament
was applied perpendicularly to the plantar surface of the paw. The
“up-and-down” method (sequential increase and decrease of the stimulus
strength) was used to determine the withdrawal threshold Dixon’s
nonparametric method was used for data analysis, as described by Chaplan
et al (Chaplan, Bach, Pogrel, Chung & Yaksh, 1994). Data were expressed
as the mean withdrawal threshold.