5-HT(1B/1D) serotonin receptor agonist attenuates nitroglycerin-evoked nitric oxide synthase expression in trigeminal pathway.

This study was conducted to investigate the effect of 5-HT(1B/1D) receptor activation on nitroglycerin (NTG)-induced cerebral hyperaemia and neuronal nitric oxide synthase (nNOS) expression in trigeminovascular neurones. NTG (10 mg/kg) was infused intravenously to adult male Wistar rats with or without pretreatment with 5-HT(1B/1D) receptor agonist, sumatriptan (0.4 mg/kg, intravenously). Cortical blood flow and expression of nNOS enzyme in trigeminal ganglia, trigeminal nucleus caudalis and perivascular nerve fibre surrounding superior sagittal sinus were measured. The results showed that pretreatment with sumatriptan could significantly shorten the period of NTG-induced cerebral hyperaemia without compromising the magnitude of hyperaemic peak. Sumatriptan pretreatment also attenuated the NTG-evoked expression of nNOS in all studied areas. Based on these findings, we suggest that 5-HT(1B/1D) receptor has an important role in stabilizing the trigeminovascular system by attenuating the expression of nNOS enzyme, hence reducing nitric oxide production.