Fig. 2. (A ) The bar graph illustrates the median relative threshold of masseter muscle afferent fibers. Lines indicate the interquartile range. The median relative threshold was significantly lowered 30 min after injection of glutamate (Glu, n = 9), but not after dextrose (Dex, n = 9) or glutamate and kynurenate (Glu & Kyn, n = 8), when compared with isotonic saline (IS, n = 8; *P < 0.05, Dunn test). (B ) The bar graph indicates the mean duration of lidocaine-induced blockade of these afferent fibers. Error bars indicate SD. Preinjection of glutamate or dextrose significantly shortened lidocaine block duration compared with isotonic saline (#P < 0.05 compared with isotonic saline, Student-Newman-Keuls test). Preinjection of glutamate resulted in a significantly shorter duration of lidocaine block than preinjection of dextrose ($ P < 0.05 compared with glutamate, Student-Newman-Keuls test). Glutamate-related shortening of lidocaine block duration was significantly attenuated by coinjection of kynurenate ($ P < 0.05 compared with glutamate, Student-Newman-Keuls test).