Endogenous Neuropeptides

Endorphin An endogenous opiate neuropeptide (endogenous morphine). 

Endogenous antipyretics include certain cytokines, neuropeptides, glucocorticoids, hormones, nitric oxide, and others. 

The hormone peptide YY (PYY) is a 36 amino acid peptide, which is closely related to neuropeptide Y and pancreatic polypeptide. PYY is predominantly synthesised and released by intestinal endocrine cells, and can also coexist with glucagon in pancreatic acini and enteroglucagon in endocrine cells of the lower bowel. It acts on the same receptors as neuropeptide Y. The endogenous long C-terminal PYY fragment PYY3 36 is a biologically active and subtype-selective metabolite. 

The endogenous release of the potent vasoconstrictor neuropeptide Y (NPY) is increased during sepsis and the highest levels are detected in patients with shock (A8). NPY is a 36-amino-acid peptide belonging to the pancreatic polypeptide family of neuroendocrine peptides (T2). It is one of the most abundant peptides present in the brain and is widely expressed by neurons in the central and peripheral nervous systems as well as the adrenal medulla (A3). NPY coexists with norepinephrine in peripheral sympathetic nerves and is released together with norepinephrine (LI9, W14). NPY causes direct vasoconstriction of cerebral, coronary, and mesenteric arteries and also potentiates norepinephrine-induced vasoconstriction in these arterial beds (T8). It appears that vasoconstriction caused by NPY does not counterbalance the vasodilatator effects of substance P in patients with sepsis. The properties of vasodilatation and smooth muscle contraction of substance P are well known (14), but because of the morphological distribution and the neuroendocrine effects a possible stress hormone function for substance P was also advocated (J7). Substance P, which is a potent vasodilatator agent and has an innervation pathway similar to that of NPY, shows a low plasma concentration in septic patients with and without shock (A8). 

Mass spectrometry has been applied mainly in proteome research, but also in discovery and quantitation of neuropeptides that are involved in pain mechanisms, such as nocistatin, substance P, or verification of, for example, the structure of endogenous morphine in the central nervous system. Some proteomics studies of pain are aimed at the search for pain markers in cerebrospinal fluid, as it may reflect changes in brain and spinal cord functioning. Another research area concerns proteome analysis in cancer pain using spinal cord tissue and animal models. 

Glycine plays an important inhibitory role in the lower brain stem and spinal cord. Little is known about the synthesis of glycine. It activates a Cl- channel, which is antagonized by strychnine. Other endogenous amino acids may activate the glycine channel, such as taurine and j8-alanine. Neuropeptides... 

Endorphins, dynorphins, and enkephalins are a particularly interesting group of neuropeptides. They act as endogenous opiates by producing analgetic, sedative, and euphoriant effects in extreme situations. Drugs such as morphine and heroin activate the receptors for these peptides (see p. 354). 

---