Effects of LY393053 (A) and AIDA (B) on the background activity in the MAN in noninflamed control rats. No significant effects on the background activity were observed for these 2 compounds after each dose was infused into spinal cord for 1 hour. Dose response curves were drawn with the spike rate plotted against the drug concentrations. Calculated concentrations applied to the spinal cord through the microdialysis fiber for LY393053 (A) were 0.01, 0.1, 1.85, and 113 μmol/L. The concentrations that were applied for AIDA (B) were 0.03, 0.3, 3, and 30 μmol/L.