Fig. 3. Effects of an intrathecal glutamate transporter activator (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153) and inhibitors (DL-threo-β-benzyloxyaspartate [TBOA], dihydrokainate, and DL-threo-β-hydroxyaspartate [DL-THA]) on formalin-induced pain behaviors. Although intrathecal MS-153 did not change the number of formalin-evoked flinches and shakes in either phase of the observational session (A ), intrathecal TBOA (B ), dihydrokainate (C ), and DL-THA (D ) decreased the number of formalin-evoked flinches and shakes in the second phase significantly and in a dose-dependent manner. *P < 0.05 or **P < 0.01 versus saline (0).