Endogenous morphine

It is now well accepted that endogenous morphine is present in animals, bot h in invertebrates and vertebrates. It is a key signaling molecule that pla ys an important role in downregulating physiological responses, such as tho se in the immune system, including immune elements in the CNS, It has been demonstrated that a specific mu-opiate-receptor subtype, mu 3, mediates the se downregulatory effects through release of NO,This article examines morph ine as an endogenous signaling molecule, in terms of its role in neural and immune regulation.