Substance P (SP) is a neuropeptide and belongs to the tachykinin neuropeptide family. It is closely related to neuropeptide neurokinin A (NKA). It is a chain of amino acids that is involved in transmitting pain and anxiety. This means, its function is carrying out communication between nerve cells. It was discovered by Ulf von Euler and John H. Gaddum in the year 1931. They extracted the substance from a tissue in vitro. It is present in the spinal cord and the brain. It tends to bind to a receptor molecule, that helps relay signals to the central nervous system. SP receptors belong to a family of receptors called the neurokinin 1 receptors. So, the minute one begins to feel pain or inflammation on the skin, muscles, joints, etc., it is transmitted to the brain. It is associated with different pains such as the lower back pain, fibromyalgia, and arthritis. Fibromyalgia occurs when there is up to three times more than the normal level of substance P in the cerebrospinal fluid.
Studies have shown that it is not only associated with pain but also other neurological processes. The neurotransmitters help in regulation of mood disorders, anxiety, stress, respiratory rhythm, neurotoxicity, nausea, etc. They are released in the peripheral terminals of the skin, muscles, and joints.
Iy is involved with the neural process of encoding and processing tissue damage. Substance P fibromyalgia is one of the most studied pain disorders. It has been seen that capsaicin helps in reducing the level. It tends to reduce the C fiber nerves, and makes them more tolerant to pain. Thus, capsaicin is added to ointments as an analgesic and anti-inflammatory agent. It helps in reducing chronic pain due to neuralgia and arthritis.
When tested in a cell growth culture, it has been found that the neuropeptide functions as a stimulator for cell growth. This means, one could use this trait of substance P in the treatment of non-healing ulcers.
There are high concentrations of substance P along with its NK1 receptors found in the vomiting center of the brain. Thus, it tends to regulate vomiting in a person. There are many antagonists available in drug stores that help in treating nausea and vomiting.
Other than the vomiting reflex, it is also seen affecting other physiological activities, like changes in the cardiovascular tone, stimulation of salivary secretion, defensive behavior, smooth muscle contraction, etc. There are many drugs and ointments been made today, as people have understood capsaicin helps in reducing the level of substance P. Thus, it helps in reducing pain and inflammation.