Substance P

In neuroscience, Substance P is a neuropeptide: a short-chain polypeptide that functions as a neurotransmitter. It is especially involved in the transmission of pain impulses from peripheral receptors to the central nervous system (it derives its name from the first letter of pain).

It has been theorised that it plays a part in fibromyalgia. Capsaicin has been shown to reduce the levels of Substance P.