H1 receptors couple to Gq/G11 proteins leading to phospholipase C activation, inositol phosphate production and calcium mobilization.nH1 receptors are expressed in many cell types including endothelial and smooth muscle cells where they mediate vasodilatation and increased vascular permeability effects.nH1 receptors are widely distributed through the brain where the mediate sleep-wake cycles and regulate cognitive functions.nH1 receptors are expressed in a several cell populations involved in the immune response, including T-cells and B-cells, monocytes and eosinophiles
