Fig 2.

Medullary sections (20 µm thick) within 1 mm caudal to the Vi/Vc border were harvested from naïve rats, rats with dural cannulation only and rats receiving either SIF or IM in the absence or presence of systemic sumatriptan. Sections were prepared for DAB staining to visualize FOS expression, and the numbers of FOS-positive profiles within the TNC were counted. Significant (P < 0.05) differences among mean counts for each group were determined by ANOVA followed by Student-Neuman-Keuls post-hoc test. Each group represents a total of 20 sections obtained from 4 rats. The results indicate that cannulation surgery alone produced a significant elevation in trigeminal FOS expression compared to the naïve rats, and SIF administration further enhanced FOS expression. Dural administration of IM produced a significantly greater increase in FOS expression when compared to SIF-treated rats, and this expression was reduced to the same level as the SIF-treated group by administration of sumatriptan.