one week following surgery animals were individually placed in a lucite testing chamber with a wire mesh bottom mechanical tactile allodynia was measured by recording the pressure at which the affected paw was withdrawn from graded stimuli von frey hairs ranging from 4 0 to 148 1 mn equivalent to 0 25 to 15 g of pressure applied to the plantar surface of the paw between the footpads according to the procedure of chaplan et al 1994 in order to calculate paw withdrawal threshold pwt normal rats can withstand at least 15 g of pressure without responding snl rats can respond to as little as 0 25 g of pressure rats were included in this study only if their pwt was below 4 0 g animals were used for compound testing between 2 weeks and 8 weeks post operatively animals were always pre tested for baseline withdrawal threshold on the day of testing following a 16 h fast pwt was evaluated at 30 min 1 h 2 h and 4 h post dosing dose response studies were conducted at the time of peak effect studies were conducted in a blinded manner data were normalized and results were presented as mpe maximum possible effect of the drug the effect of example compounds is presented in table 3 and cpd 3 had an.