Background: Clinical studies indicated that nitric oxide (NO) donors cause regional changes in cerebral blood flow (CBF), similar to those reported in spontaneous migraine. Systemic nitroglycerin (NTG), a NO donor, is a well-accepted experimental model of migraine. In this study we have examined the effects of NTG on the meningeal and cortical blood flow in rats.
Methods: Regional blood flow was monitored in male Sprague-Dawley rats using laser Doppler flowmetry before and after NTG/saline injection over 150 minutes. The effect of pre-treatment with Nω-nitro-L-arginine ester (L-NAME) or 7-nitroindazole (7-NI) on NTG-induced changes on blood flow was also investigated.
Results: In the dura NTG caused a biphasic response represented by an initial decrease in blood flow followed by a significant increase. At variance, in the cortex NTG caused only an increase in blood flow. Pre-treatment with either L-NAME or 7-NI prevented NTG-induced increase in blood flow in both districts, while only L-NAME also prevented NTG-induced decrease in dural blood flow.
Conclusion: The present findings provide additional information on the timing of effects of NTG on blood flow at both the meningeal and cortical levels. These effects seem to be related to vasoregulatory mechanisms and/or metabolic activity in response to the synthesis of endogenous NO.