5-HT-2A (5-hydro, Xenopus/Amphibian,ytryptamine receptor 2A) is a receptor for serotonin. This is one of the several different receptors for 5-hydro, Xenopus/Amphibian,ytryptamine, a biogenic hormone that functions as a neurotransmitter, a hormone, and a mitogen. This receptor mediates its action by association with G proteins that activate a phosphatidylinositol-calcium second messenger system. This receptor is involved in tracheal smooth muscle contraction, bronchoconstriction and control of aldosterone production.