GC: n
S: NCBI – https://pubmed.ncbi.nlm.nih.gov/12969194/ (last access: 27 October 2024); NIH – https://pubmed.ncbi.nlm.nih.gov/10098939/ (last access: 27 October 2024).
N: 1. endomorph. n. 1940 as one of W.H. Sheldon’s three types of human bodies, from “endo-” + “-morph”, from Greek morphē “form,” a word of uncertain etymology. Earlier, “a mineral encased in the crystal of another mineral” (1874). Related: Endomorphic.
endomorphin. n. From “endo-” (word-forming element meaning “inside, within, internal,” from Greek endon “in, within”; from PIE *en-do-, extended form of root *en “in”) and “morphine” (chief alkaloid of opium; used as a narcotic pain-killer, 1828, from French morphine or German Morphin (1816), name coined by German apothecary Friedrich Sertürner (1783-1840) in reference to Latin Morpheus (q.v.), Ovid’s name for the god of dreams, from Greek morphē “form, shape, beauty, outward appearance,” which is of unknown origin. So called because of the drug’s sleep-inducing properties).
2. Endomorphins are considered to be natural opioid neuropeptides central to pain relief. The two known endomorphins, endomorphin-1 and endomorphin-2, are tetrapeptides, consisting of Tyr-Pro-Trp-Phe and Tyr-Pro-Phe-Phe amino acid sequences respectively
3. Endomorphins are endogenous peptides that were relatively recently isolated from bovine and human brain (Zadina et al., 1997; Hackler et al., 1997). These peptides differ in their amino acid sequences from other known EOPs; rather than having a Tyr residue followed by Gly, endomorphins resemble members of another related family of peptides (e.g., morphiceptin, hemorphin, and casomorphins) that instead contain Tyr–Pro residues. Endomorphins are localized in neuronal circuits involved in processing nociceptive information and also in many stress-responsive areas of the brain and autonomic nervous system where MOP receptors are present (Zadina et al., 1999). Endomorphins act as endogenous ligands of MOP receptors and thus are important in modulating responses to pain and stress by acting on autonomic and neuroendocrine systems (Zadina, 2002; Wang et al., 2003; Glatzer and Smith, 2005; Silverman et al., 2005; Greenwell et al., 2007). In addition, the common distribution of endomorphins and other neurotransmitters suggests their modulatory role in neurotransmission (Greenwell et al., 2007).
4. Endomorphin 1 (EM1) and endomorphin 2 (EM2) are highly potent and selective μ-opioid receptor agonists and have significant antinociceptive action. In the μ-selective pocket of endomorphins (EMs), Pro2 residue is a spacer and directs the Tyr1 and Trp3/Phe3 side chains into the required orientation. The present work was designed to substitute the peptide bond between Tyr1 and Pro2 of EMs with a reduced (CH2NH) bond and study the agonist potency and antinociception of EM1[ψ] (Tyr[ψ(CH2NH)]Pro-Trp-Phe-NH2) and EM2[ψ] (Tyr[ψ(CH2NH)]Pro-Phe-Phe-NH2). Both EM1[ψ] and EM2[ψ] are partial μ opioid receptor agonists showing significant loss of agonist potency in GPI assay. However, EMs[ψ] exhibited potent supraspinal antinociceptive action in vivo. In the mice tail-flick test, EMs[ψ] (1, 5, 10 nmol/mouse, i.c.v.) produced potent and short-lasting antinociception in a dose-dependent and naloxone (1 mg/kg) reversed manner. At the highest dose of 10 nmol, the effect of EM2[ψ] was prolonged and more significant than that of EM2. In the rat model of formalin injection induced inflammatory pain, EMs[ψ] (0.1, 1, 10 nmol/rat, i.c.v.), like EMs, exerted transient but not dose-dependent antinociception. These results suggested that in the μ-selective pocket of EMs, the rigid conformation induced by the peptide bond between Tyr1 and Pro2 is essential to regulate their agonist properties at the μ opioid receptors. However, the increased conformational flexibility induced by the reduced (CH2NH) bond made less influence on their antinociception.
S: 1. Etymonline – https://www.etymonline.com/search?q=endomorph, https://www.etymonline.com/search?q=endo-, https://www.etymonline.com/search?q=morphin (last access: 27 October 2024). 2. Wikipedia – https://en.wikipedia.org/wiki/Endomorphin (last access: 27 October 2024). 3 & 4. SDir – https://www.sciencedirect.com/topics/neuroscience/endomorphin, https://www.sciencedirect.com/science/article/abs/pii/S0024320505003280 (last access: 27 October 2024).
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