<unk>  is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since<unk>  was discovered in 1910, it<unk> as been considered as a local<unk> ormone (autocoid) because it lacks the classic endocrine glands to secrete it,<unk> owever, in recent years,<unk> <unk> as been recognized as a central neurotransmitter.<unk>  is involved in the inflammatory response and<unk> as a central role as a mediator of itching. As part of an immune response to foreign pathogens,<unk>  is produced by basophils and by mast cells found in nearby connective tissues.<unk>  increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues. It consists of an imidazole ring attached to an ethylamine chain; under physiological conditions, the amino group of the side-chain is protonated.
Histamine
Leukotriene
Serotonin
Nitric oxide
Antileukotriene
Defensin
Acetylcholine
Interleukin