Fig. 2

Analysis of the mechanical threshold of rats with NTG-induced migraine. Multiple NTG administrations evoked and sustained mechanical hyperalgesia. Rats were treated every 2 d with varying doses of NTG (0, 2.5, 5 and 7.5 mg/kg, s.c., daily or 0, 5, 10 and 15 mg/kg, s.c., every 2 d) for 9 d. (A) Basal mechanical threshold of all groups during NTG administration. (B) Posttreatment NTG mechanical threshold of all groups during NTG administration. (C-E) Mechanical threshold of the rats with migraine administered NTG s.c. daily for 9 d. (F) Mechanical threshold of the rats administered consecutive NTG s.c injections on the 9th day. (G-I) Mechanical threshold of the rats with migraine administered NTG s.c. every 2 d for 9 d. (J) Mechanical threshold of the rats s.c. administered intermittent NTG on the 9th day. Each dose group was significantly different from the vehicle group (p < 0.05), and each dose also produced significantly different results from the other doses (p < 0.05). NTG produces dose-dependent and persistent hyperalgesia in rats. Statistical analysis was performed using one–way ANOVA, n = 6, *p < 0.05 compared to the basal mechanical threshold