Substance P is an undecapeptide belonging to the tachykinin neuropeptide family. It functions as a neurotransmitter and neuromodulator.
Synthesis:
Neurons: Primarily synthesized in the central and peripheral nervous systems.
Release: Released from sensory nerve endings in response to pain and inflammation.
Functions:
Neurotransmission: Transmits pain signals from peripheral nerves to the central nervous system.
Vasodilation and Increased Permeability: Contributes to inflammatory responses by acting on blood vessels.
Immune Modulation: Influences immune cell activity and cytokine release.
Smooth Muscle Contraction: Affects gastrointestinal and respiratory tract motility.
Receptors:
Neurokinin-1 (NK1) Receptors: High affinity for substance P; involved in pain transmission and inflammatory responses.
Neurokinin-2 (NK2) and Neurokinin-3 (NK3) Receptors: Bind substance P with lower affinity; have distinct physiological roles.
Clinical Relevance of Substance P:
Pain Management: NK1 receptor antagonists are explored for treating chronic pain and depression.
Emesis Control: NK1 antagonists like aprepitant are used to prevent chemotherapy-induced nausea and vomiting.
Inflammatory Diseases: Potential targets for treating conditions like asthma and arthritis.