Fig. 2

Orexin neurons modulate pain and itch sensations in an opposite way. A Illustration of the wiping behavior using a single forelimb (pain-related behavior). B Time course of the number of wiping behaviors induced by capsaicin injection into the cheek. The plots indicate the cumulative number of wiping events recorded every 5 min. C The number of wiping events within 30 min after capsaicin injection was significantly increased in ORX-abl mice (n = 8) compared with WT mice (n = 8). D Illustration of the scratching behavior using the hind leg (itch-related behavior). E Time course of the number of scratching bouts induced by chloroquine injection into the right cheek. The plots indicate the cumulative number of scratching bouts recorded every 5 min. F The number of scratching bouts within 30 min after chloroquine injection was significantly decreased in ORX-abl mice (n = 9) compared with WT mice (n = 10). The data represent the mean ± SEM. *P < 0.05, **P < 0.01 (two-way ANOVA with post hoc Tukey’s multiple comparisons test)