Mechanical withdrawal threshold ipsilateral and contralateral to neuritis. Withdrawal threshold to von Frey stimulation ipsilateral (A) and contralateral (B) to neuritis before and after catheter implantation, 24 hr after zymosan (40 μg) plus saline (Z+S), zymosan plus clonidine (30 μg; Z+C) and zymosan plus BRL44408 (45 μg) plus clonidine (30 μg; Z+BR+C). Withdrawal threshold to von Frey stimulation ipsilateral (C) and contralateral (D) to neuritis before and after catheter implantation, and 3 days after zymosan (40 μg) plus saline, vehicle plus saline (V+S), zymosan plus clonidine (30 μg) and zymosan plus BRL44408 (45 μg) plus clonidine (30 μg). Withdrawal thresholds were significant reduced (P<0.05) 3 hr after zymosan injections compared to the value observed before catheter implantation. *P<0.05 compared to zymosan plus saline group; #P<0.05 compared to vehicle or zymosan plus saline group. *P<0.05 compared to zymosan plus saline group. +P<0.05 compared to zymosan plus BRL44408 plus clonidine group.