Principle mediator of vasodilation in acute inflammation is

Vasodilation is induced by chemical mediators such as histamine and is the cause of erythema and stasis of blood flow in acute inflammation.Histamine causes dilation of aerioles and increases the permeability of venules. Histamine is considered to be the principal mediator of the immediate transient phase of increased vascular permeability, producing interendothelial gaps in venules. Its vasoactive effects are mediated mainly binding to receptors, called H1 receptors, on microvascular endothelial cells. The antihistamine drugs that are commonly used to treat some inflammatory reactions, such as allergies, are H1 receptor antagonists that bind to and block the receptor.Ref: Robbins and Cotran Pathologic Basis of Disease; 9th edition; Chapter 3; Acute inflammation; Page no: 75