Neuropeptide biological actions

The unique primary sequence of each neuropeptide defines its selective and potent biological actions. The same neuropeptides often serve important functions in both the nervous system as neurotransmitters (Fig. 1) and as peptide hormones in peripheral endocrine systems. For example, enkephalins function as neurotransmitters in the brain and are involved in peripheral actions, including regulation of intestinal motility and immune... 

McDonald, J.K. Koenig, J.I. (1993) Neuropeptide Y actions on reproductive and endocrine functions. In The Biology of Neuropeptide Y and Related Peptides (eds Colmers, W.F. Wahlestedt, C.) pp. 419—456. Totowa, NJ, Humana Press Inc. 

Mammalian tachykinins, a family of tachykinin peptides traditionally classified as neurotransmitters that include substance P (SP), neurokinins (NKA and NKB), two elongated versions of NKA, neuropeptide y (NP,) and neuropeptide K (NPK), hemokinin 1 (HK-1) and endokinins A-D. They act as neurotransmitters, paracrine or endocrine factors, neuroimmunomodulators, and have also immune and pro-inflammatory actions. Furthermore, mammalian tachykinins are involved in vasodilation, plasma extravasation, smooth muscle contraction, secretion, neural excitation, and processing of sensory information. The biological actions are mediated via three known mammalian tachykinin receptors, NKi, NK2, and NK3 [N. M. Page et al, Proc. Natl. Acad. Sci. USA 2003, 100, 6245 N. M. Page, Peptides 2005, 26, 1356 L. Liu, E. Burcher, Peptides 2005, 26, 1369]. 

The mammalian carotid body expresses a variety of neurochemicals and their receptors (see Tables 1 and 2). The transmitters expressed in the carotid body can be classified into two major categories conventional and imconventional. The conventional class of neurotransmitters includes those that are stored in vesicles and exert their effect via activation of specific receptors. Examples of this class include catecholamines, acetylcholine, and neuropeptides, whereas gas molecules like nitric oxide (NO) and carbon monoxide (CO) form the class of unconventional neurotransmitters. These molecules are generated spontaneously by way of enzymatic reactions and mediate their biological actions by either activation... 

The biological actions of capsaicin are primarily attributable to release of the neuropeptide substance P, calcitonin gene-related peptide (CGRP), and neurokinin A from sensory neurons. These transmitters from primary sensory neurons communicate witir other cell types. They produce alterations in the airway mucosa and neurogenic inflammation of the respiratory epithelium, airway blood vessels, glands, and smooth muscle. Alterations in multiple effector organs lead to bronchoconstriction, increased vascular permeability, edema of the tracheobronchial mucosa, elevated mucosal secretion, and neutrophil chemotaxis (Tominack and Spyker, 1987). Capsaicin-induced effects of bronchoconstriction, vasodilation, and plasma protein extravasation are mediated by substance P. In addition, substance P can cause bronchoconstriction through stimulation of c-fibers in pulmonary and bronchial circulation. 

Raina A. K., Kempe, T. G. and Jaffe H. (1991) Pheromone biosynthesis-activating neuropeptide Regulation of pheromone production in moths. In Insect Neuropeptides Chemistry, Biology and Action, eds J. J. Menn, T. J. Kelly and E. P. Masler, pp. 100-109. American Chemical Society, Washington, DC. 

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