Distribution of c-Fos-positive neurons in the cords incubated in normal aCSF (A) or aCSF containing 0.5 μM TTX (B), 20 μM MECA (C), or 800 μM KYN (D). c-Fos-positive neurons are revealed by double labeling of NeuN-IR (FITC) and c-Fos-IR (rhodamine). Compared with the control (Ai), c-Fos expression in the dorsal laminae neurons was apparently reduced by TTX (Bi) or MECA (Ci) but not by KYN treatment (Di). In the IML, the abundance of c-Fos-positive neurons was diminished only by MECA (Cii), but not by TTX (Bii) or KYN treatment (Dii). Scale bars = 100 μm in (A-D), 20 μm in (Ai-Di), and 10 μm in (Aii-Dii).