nNOS immunoreactivity 4 h after IS treatment Representative photomicrographs of the nNOS expression in the trigemino-cervical segments after 4 h. a – SIF, b – IS, c – SUMASIF, d – SUMAIS, e – KYNSIF, f – KYNIS. In the IS group, the number of nNOS-IR cells was increased compared to the SIF- treated group. Sumatriptan and kynurenic acid were able to mitigate this effect. SIF: synthetic interstitial fluid, IS: inflammatory soup, SUMASIF: sumatriptan + synthetic interstitial fluid, SUMAIS: sumatriptan + inflammatory soup, KYNSIF: kynurenic acid + synthetic interstitial fluid, KYNIS: kynurenic acid + inflammatory soup. Scale bars: 200 μm, 50 μm.