Drug-induced changes in SND genesis and in the numbers of c-Fos-positive IML neurons. The spinal cords were incubated in normal aCSF (control) or aCSF containing 0.5 μM TTX, 20 μM MECA, or 800 μM KYN. (A) Original traces of the sSND envelope. sSND was abolished or reduced in cords incubated in aCSF containing TTX or MECA, but not apparently affected by application of KYN. (B) Numbers of c-Fos-positive neurons in the IML. The numbers were obtained from averaging counts of IML cells double labeled for c-Fos-IR and NeuN-IR in transverse sections of T3 spinal cord segments (30-μm-thickness). Compared with the control (8.2 ± 1.1; n = 6), the number of c-Fos-positive neurons was significantly reduced by application of MECA (3.8 ± 0.5; n = 5; P < 0.01), but not by application of TTX (6.2 ± 1.3; n = 5) or KYN (8.5 ± 0.6; n = 8).