Effect of serotonin depletion on nitric oxide induced cerebrovascular nociceptive response

The study was conducted to investigate the effect of serotonin depletion on nitric oxide-induced meningeal vascular response and cerebrovascular nocic eption. Nitroglycerin was infused i.v. to control and serotonin-depleted ra ts. Pial circulation was monitored by intravital fluorescent videomicroscop y and Fos immunoreactivity trigeminal nucleus caudalis neurons was used as an indicator for the cerebrovascular nociception. The results showed that t he degree of nitric oxide-induced pial microvascular dilatation was signifi cantly greater in the serotonin-depleted group than the control. The number of nitric oxide-evoked Fos-immunoreactive cells between the two groups rem ained comparable. The results suggest that though depletion of serotonin ca n facilitate the vascular response to nitric oxide it does not alter the ni tric oxide-induced craniovascular nociceptive response. NeuroReport 12:967- 971 (C) 2001 Lippincott Williams & Wilkins.