SNAP, a nitrosothiol derivative, releases nitric oxide (NO.) under physiological conditions thus making it a useful tool for studying pharmacological and physiological actions of NO. Because of its NO releasing properties SNAP is a potent vasodilator in vitro and in vivo and is less prone to produce pharmacological tolerance.Nitric oxide (NO) donor; vasodilator, smooth muscle relaxant, lymphocyte activator. SNAP, a nitrosothiol derivative, releases nitric oxide (NO.) under physiological conditions thus making it a useful tool for studying pharmacological and physiological actions of NO. Because of its NO releasing properties SNAP is a potent vasodilator in vitro and in vivo and is less prone to produce pharmacological tolerance. Nitric oxide (NO) donor; vasodilator, smooth muscle relaxant, lymphocyte activator.