Figure 9.
Itch signal descending from ACC-DMS projections is modulated by GRPRs in the spinal cord. A, Schematic illustration of ACC-DMS projections in brain and pruritic neurons in the spinal cord. B, C, Photoactivation of ACC-DMS elevated c-fos expression in the dorsal horn of spinal cord. t(10) = 4.756, p = 0.0008. Scale bar, 50 μm. D, Intrathecal injection of the GRPR antagonist (10 nmol) significantly reduced scratching behavior evoked by histamine (500 μg/50 μl). F(2,21) = 4.216; 10 nmol, p = 0.0289. E, GRPR antagonist significantly suppressed scratching behavior induced by photoactivation of ACC-DMS projections. Mice expressing ChR2-EYFP were injected with (D-Phe12, Leu14)-bombesin (10 nmol/5 μl, i.t.) before being illuminated by light. t(13) = 3.016, p = 0.0099. Data are shown as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 compared with vehicle groups. Data in C and E were analyzed by Student's t test and data in D were analyzed by one-way ANOVA. n = 6–8 mice for each group.