The widening of blood vessels—it lowers blood pressure and increases blood flow to tissues.Vasodilation is the relaxation of vascular smooth muscle, increasing vessel diameter, blood flow, and reducing peripheral resistance. Peptide-mediated vasodilation occurs through multiple mechanisms: VIP activates VPAC1/2 receptors on vascular smooth muscle (cAMP-mediated relaxation); CGRP is the most potent known endogenous vasodilator (acting through CLR/RAMP1); BNP/nesiritide activates NPR-A/cGMP signaling. Vasodilation is both a therapeutic mechanism (nesiritide in heart failure) and a dose-limiting adverse effect (hypotension with VIP, CGRP).