LY334370 is a selective 5-HT_1F receptor agonist with a K_i of 1.6 nM. IC50 & Target: Ki: 1.6 nM (5-HT_1F) In Vitro: LY334370 has no vasoconstrictor effects on human cerebral arteries in vitro until a dose of 10^-5 M, at which it produces a contraction of 8.5±5.7%; however, this is not significant^[1]. In Vivo: Following intravenous administration of LY334370 at 3 mg/kg (n=3) or 10 mg/kg (n=6) electrical stimulation evokes an increase in dural blood vessel diameter of 135±6% and 106±11%, respectively, which is not significantly different from the respective control values. LY334370 has no effect on dural blood vessel diameter per se, since the actual dural blood vessel diameter is 43±4 arbitrary units before drug and 43±4 arbitrary units 15 min after injection of LY334370 (10 mg/kg)^[1].