Figure 4.

Effect of capsaicin and 5′-Iodo-resiniferatoxin (I-RTX) on the spontaneous firing of RVM ON (A, C) or OFF (B, D) cells. A and B show the effect of intraventrolateral PAG administration of vehicle, capsaicin (3 and 6 nmol/rat) alone, or capsaicin (6 nmol/rat) in combination with I-RTX (0.5 nmol/rat). C and D shown the effect of I-RTX (0.5 and 1 nmol/rat) alone. The black arrow indicates drug microinjections. Each point represents the mean ± SEM of 8–10 neurons. * indicates significant differences versus vehicle; ° indicates significant differences versus capsaicin (6 nmol/rat). p values <0.05 were considered statistically significant.