China
Africa
Explore chapters and articles related to this topic
Clinical pharmacology of opioids: basic pharmacology
Published in Nigel Sykes, Michael I Bennett, Chun-Su Yuan, Clinical Pain Management, 2008
Sangeeta R Mehendale, Chun-Su Yuan
Opioid peptides are endogenously produced predominantly in the central nervous system and the spinal cord.37 The three distinct families of peptides, endorphins, enkephalins, and dynorphins, are natural agonist ligands for opioid receptors mu, delta, and kappa, respectively (Table 12.1).35 Each family of opioid peptides is derived from a distinct precursor molecule, with proopiomelanocortin, proenkephalin, and prodynorphin being precursors of endorphins, enkephalins, and dynorphins, respectively. Of the relatively newly discovered endogenous opioid-related peptides, endomorphin-1 and -2 are selective, potent mu-receptor agonists that demonstrate a significant degree of analgesic activity.42, 43 Endomorphin-1 at equianalgesic doses appears to cause less severe respiratory depression compared with other mu agonists,43 suggesting that it may act on specific mu receptor subtypes.44 Another notable endogenous peptide orphanin NQ/nociceptin, a ligand to receptor ORL-1, plays a complex role in producing analgesia and is being investigated.45
Clinical pharmacology: opioids
Published in Pamela E Macintyre, Suellen M Walker, David J Rowbotham, Clinical Pain Management, 2008
David J Rowbotham, Alcira Serrano-Gomez, Anne Heffernan
Endogenous ligands acting at opioid receptors include enkephalins (δ receptor), dynorphins (κ receptor), endorphins (high affinity, but poor selectivity for μ receptors),41 and nociceptin/orphanin FQ (NOP receptor, see below under Nociceptin/orphanin FQ receptor). The endogenous selective ligands for the μ receptor (endomorphins) were first identified in 1997.29 Both endomorphin 1 and endomorphin 2 are peptides of four amino acids and intimately involved in nociceptive pathways.42 Unlike the other recognized peptides, precursors for endomorphin 1 and 2 have not been identified.
The potential interplay between opioid and the toll-like receptor 4 (TLR-4)
Published in Immunopharmacology and Immunotoxicology, 2023
Nasrin Zare, Marjan Pourhadi, Golnaz Vaseghi, Shaghayegh Haghjooy Javanmard
Opioids are classified base on the type of opioid receptors. These receptors are located on neuronal cell membranes and all the receptors (the delta receptor or DOP, the kappa receptor or KOP, the mu receptor or MOP, and nociceptin receptor or NOP) are a member of the large family of G-protein-coupled receptors. Pharmacological investigations demonstrate that enkephalins interact with delta receptors or DOP, dynorphin with k receptors or KOP and β-endorphin and endomorphin 1 and 2 with m receptors or MOP and nociceptin receptor or NOP with nociceptin/orphanin FQ (N/OFQ). As well, most clinical drugs such as morphine (a potent alkaloid in opium), Fentanyl/remifentanil, buprenorphine, codeine, and methadone bind to MOP receptors. Furthermore, the opioid antagonist (naloxone and naltrexone) could inhibit all opioid receptors; however, they have the most affinity for m receptors [3–6].
Neuropharmacological basis for multimodal analgesia in chronic pain
Published in Postgraduate Medicine, 2022
Ryan Patel, Anthony H Dickenson
The pain-relieving properties of naturally occurring opioids have been utilized for centuries, and today opioids remain the mainstay of treating acute and chronic pain. Morphine has become the gold standard analgesic to which all others are compared. The classical opioid receptors μ, δ and κ are G-protein coupled, and later a fourth opioid-like receptor (ORL1) was described and renamed the nociceptin receptor. Soon after, a series of endogenous peptide ligands were described. Most of these bind to multiple receptors through endomorphin-1/2 and β-endorphin have highest affinity for μ-opioid receptors, met- and leu-enkephalin have highest affinity δ-opioid receptors, dynorphin A/B have highest affinity κ-opioid receptors, and nociceptin/orphanin FQ has highest affinity for the nociceptin receptor [69]. Upon receptor activation neuronal excitability or action potential propagation is inhibited by several mechanisms including opening of G protein–coupled inwardly rectifying potassium channels [70], inhibition of sodium [71] and calcium channels [72], and inhibition of Ih currents [73].
Nanotechnology application for pain therapy
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Mahmoud Reza Moradkhani, Arash Karimi, Babak Negahdari
Hua and Cabot also reported the use of targeted nanoparticles to deliver opioids, in particular, loperamide HCl, specifically to peripheral opioid receptors to stimulate analgesic and anti-inflammatory actions for use in painful inflammatory conditions [18]. Ward et al. also reported other sustained engineered release systems to extend the duration of action of opioid analgesics [19]. Liu and colleagues in their report demonstrated that endomorphin-1, adsorbed onto the surface of butyl- cyanoacrylate nanoparticles and coated with polysorbate 80 could be administered intravenously as an analgesic agent [20]. Furthermore, Tosi and co-worker investigated the antinociceptive efficacy of peptide-derivatized nanoparticles loaded with loperamide HCl in an in vivo experiment for delivery to central opioid receptors. They concluded that there was a peak percentage of possible effect of 60% at 4 h and a significant continued release effect for 6 h after the administration of 0.7 mg of loperamide HCl in Wistar rats [21]. In addition, Chen et al. reported that nanoparticles made up of loperamide and PLGA-PEG-PLGA triblock copolymer coated with poloxamer 188 or polysorbate 80 enhanced penetrations across the blood–brain barrier in comparison to PLGA-PEG-PLGA nanoparticles and PLGA nanoparticles.