Neuropeptides and Neurotransmission

Over the past four decades, many neuropeptides, that is, 3–100 amino-acid-long polypeptides, have been identified in the central nervous system and the peripheral nervous system which can act on either neural substrates such as neurons and glial cells or other target cells. Neuropeptides mediate neuronal communication by acting on neuropeptide receptors. Neuropeptide receptors include over 44 receptor families, of which most are G protein-coupled receptors. Neuropeptides and their cognate receptors are involved in various physiological and pathophysiological functions, such as pain regulation, blood pressure, body temperature, feeding behavior, reproduction, sleep, learning and memory. Therefore, neuropeptide transmission is an attractive area for drug discovery in several therapeutic areas, including inflammatory conditions, epilepsy and psychiatric diseases targeting neuropeptide receptors. This chapter elaborates and expounds on the role of various small neuropeptides such as substance P (SP), vasoactive intestinal peptides (VIP), neuropeptide Y (NPY) and endogenous opioid neuropeptides, along with their physiology, pathophysiology and pharmacology. This chapter also describes the various neuropeptide receptor agonists and antagonists and their possible roles in the treatment of various disorders.