Figure 3. Withdrawal threshold to stimulation by von Frey filaments before surgery (Base), after spinal nerve ligation (SNL), and for 60 min after cumulative intrathecal injection of a 10:1 combination of clonidine and neostigmine (top). The baseline and SNL data points represent the median +/- 25th and 75th percentiles of 10 rats, and the neostigmine and clonidine data points represent these statistics for 6 rats. *P < 0.05 versus baseline condition. (Bottom) Isobologram at the dose of clonidine alone, neostigmine alone, or their combination required to achieve a 50% return to baseline mechanical sensitivity after SNL surgery (ED⁵⁰). The combination point differs significantly from a theoretical additive interaction.