NTG-induced fos expression in wild-type and P2X7 knockout mice. A. Quantification of fos-immuno-reactive nuclei in upper cervical spinal cord (C1-2) and TNC 2 h after 15 mg/kg NTG or vehicle. We counted 10 hemi-sections from each hemisphere for upper cervical spinal cord, and 30 hemi-sections from each hemisphere that included TNC from both sides (n = 5-6 animal/group; Kruskal-Wallis nonparametric ANOVA followed by Fischer LSD post hoc test, *P < 0.05, **P < 0.01, ***P < 0.001). F. The subacute BBG treatment (50 mg/kg i.p.) decreased the number of c-fos immuno-reactive cells in TNC, but not in C1-2 in wild-type mice (n = 6-8 animal/group; Student t test **P < 0.01). B,C,D,E,G,H Representative examples of c-fos immuno-reactivity in the TNC 2 h after i.p. administration of vehicle or 15 mg/kg NTG in P2X7+/+ (B,C) and P2X7-/- mice (D,E), and after subacute BBG (50 mg/kg i.p.) or saline + 15 mg/kg NTG treatment in P2X7 +/+ mice (G,H), shown here with a 10× objective.