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Opioid antagonism

Eiko Yokota, Yuko Koyanagi, Kiyofumi Yamamoto, Yoshiyuki Oi, Noriaki Koshikawa, Masayuki Kobayashi
The insular cortex (IC) plays a principal role in the regulation of pain processing. Although opioidergic agonists depress cortical excitatory synaptic transmission, little is known about opioidergic roles in inhibitory synaptic transmission. In the IC, the opioid receptors differentially regulate the excitatory propagation: agonists of the mu (MOR), delta (DOR), and kappa (KOR) exhibit suppressive, facilitative, and little effects, respectively. Thus, we aimed to examine the effects of opioid receptor agonists on unitary inhibitory postsynaptic currents (uIPSCs) in the IC...
October 7, 2016: Neuroscience
Travis T Wager, Thomas A Chappie, David Horton, Ramalakshmi Y Chandrasekaran, Brian M Samas, Elizabeth Dunn-Sims, Cathleen Hsu, Nawshaba Nawreen, Michelle A Vanase-Frawley, Rebecca E O'Connor, Christopher Schmidt, Keith Dlugolenski, Nancy C Stratman, Mark J Majchrzak, Bethany L Kormos, David Nguyen, Aarti Sawant-Basak, Andy N Mead
Dopamine receptor antagonism is a compelling molecular target for the treatment of a range of psychiatric disorders, including substance use disorders. From our corporate compound file we identified a structurally unique D3 receptor (D3R) antagonist scaffold, 1. Through a hybrid approach, we merged key pharmacophore elements from 1 and D3 agonist 2 to yield the novel D3R/D2R antagonist PF-4363467 (3). Compound 3 was designed to possess CNS drug-like properties as defined by its CNS MPO desirability score (≥4/6)...
October 7, 2016: ACS Chemical Neuroscience
S Michael Owens, Gerald T Pollard, James L Howard, Timothy R Fennell, Rodney W Snyder, F Ivy Carroll
JDTic is a potent and selective κ-opioid receptor (KOR) antagonist that reverses U50,488-induced diuresis in rats. It partitions into brain with a duration of action lasting for weeks. In a search for KOR antagonists that do not accumulate in the brain, we compared single doses of five methylated JDTic analogs (RTI-97, -194, -212, -240, and -241) for reversal of U50,488 diuresis and pharmacokinetic (PK) properties. All six compounds showed potent and selective KOR antagonism in a [(35)S]GTPγS binding assay...
October 4, 2016: ACS Chemical Neuroscience
Rebecca C Price, Nicolas V Christou, Steven B Backman, Laura Stone, Petra Schweinhardt
RATIONALE: Endogenous opioids inhibit nociceptive processing and promote the experience of pleasure. It has been proposed that pain and pleasure lie at opposite ends of an affective spectrum, but the relationship between pain and pleasure and the role of opioids in mediating this relationship has not been tested. OBJECTIVES: Here, we used obese individuals as a model of a dysfunctional opioid system to assess the role of the endogenous opioid peptide, beta-endorphin, on pain and pleasure sensitivity...
September 22, 2016: Psychopharmacology
Marita Windpassinger, Olga Plattner, Jana Gemeiner, Kornelia Böhler, Robert Luntzer, Walter Klimscha, Dongsheng Yang, Edward J Mascha, Daniel I Sessler
BACKGROUND: The intravenous anesthetic propofol is a gamma-aminobutyric acid A receptor agonist. Propofol promotes analgesia by depressing nociceptive transmission in peripheral neurons, antagonizing N-methyl-D-aspartate receptors, and activating gamma-aminobutyric acid A receptors in dorsal root ganglion receptor cells. Nevertheless, it remains unclear whether intraoperative propofol causes clinically meaningful postoperative analgesia. We therefore tested the hypothesis that patients anesthetized with sevoflurane require a greater quantity of postoperative opioids (from the end of surgery until the next postoperative morning) than those anesthetized with propofol...
November 2016: Canadian Journal of Anaesthesia, Journal Canadien D'anesthésie
Jai Shankar K Yadlapalli, Benjamin M Ford, Amit Ketkar, Anqi Wan, Narasimha R Penthala, Robert L Eoff, Paul L Prather, Maxim Dobretsov, Peter A Crooks
: This study determined the antinociceptive effects of morphine and morphine-6-O-sulfate (M6S) in both normal and diabetic rats, and evaluated the comparative role of mu-opioid receptors (mu-ORs) and delta-opioid receptors (delta-ORs) in the antinociceptive action of these opioids. In vitro characterization of mu-OR and delta-OR-mediated signaling by M6S and morphine in stably transfected Chinese hamster ovary (CHO-K1) cells showed that M6S exhibited a 6-fold higher affinity for delta-ORs and modulated G-protein and adenylyl cyclase activity via delta-ORs more potently than morphine...
September 13, 2016: Pharmacological Research: the Official Journal of the Italian Pharmacological Society
K Wagner, K S S Lee, J Yang, B D Hammock
BACKGROUND: Neuropathic pain is a debilitating condition with no adequate therapy. The health benefits of omega-3 fatty acids are established, however, the role of docosahexaenoic acid (DHA) in limiting pain has only recently been described and the mechanisms of this action remain unknown. DHA is metabolized into epoxydocosapentanoic acids (EDPs) via cytochrome P450 (CYP450) enzymes which are substrates for the soluble epoxide hydrolase (sEH) enzyme. Here, we tested several hypotheses; first, that the antinociceptive action of DHA is mediated by the EDPs...
September 15, 2016: European Journal of Pain: EJP
Rossella De Marco, Andrea Bedini, Santi Spampinato, Lorenzo Cavina, Edoardo Pirazzoli, Luca Gentilucci
Recently, the tryptophan-containing noncationizable opioid peptides emerged with atypical structure and unexpected in vivo activity. Herein, we describe analogs of the naturally occurring mixed κ/μ-ligand c[Phe-d-Pro-Phe-Trp] 1 (CJ-15,208). Receptor affinity, selectivity, and agonism/antagonism varied upon enlarging macrocycle size, giving the μ-agonist 9 or the δ-antagonist 10 characterized by low nanomolar affinity. In particular, the μ-agonist c[β-Ala-d-Pro-Phe-Trp] 9 was shown to elicit potent antinociception in a mouse model of visceral pain upon systemic administration...
October 13, 2016: Journal of Medicinal Chemistry
Mark J Elzey, Jeffrey Fudin, Eric S Edwards
INTRODUCTION: Naloxone reversal of opioid-induced respiratory depression outside of medical facilities has become more prevalent because of the escalating opioid epidemic in the USA. Take-home naloxone for treatment of opioid emergencies is now being recommended by numerous federal, state, and professional organizations. AREAS COVERED: The scope of the opioid overdose epidemic is reviewed along with practical, clinical, regulatory, and usability considerations for take-home naloxone routes of administration currently available and associated delivery systems...
September 8, 2016: Expert Opinion on Drug Delivery
Renato Leonardo de Freitas, Priscila Medeiros, Juliana Almeida da Silva, Rithiele Cristina de Oliveira, Ricardo de Oliveira, Farhad Ullah, Asmat Ullah Khan, Norberto Cysne Coimbra
It has been proposed that the post-ictal state is associated with the expression of hypoalgesia. It is clear that the projections among the periaqueductal gray matter (PAG), dorsal raphe nucleus (DRN) and locus coeruleus (LC) play a role in pain management. These mesencephalic structures have direct reciprocal opioid and monoaminergic projections to the LC that can possibly modulate post-ictal hypoalgesia. The goal of this study was to examine if LC-opioid and serotonergic/noradrenergic mechanisms signal the post-ictal hypoalgesic responses to tonic-clonic seizures produced by intraperitoneal administration of pentylenetetrazole (PTZ at 64mg/kg), causing an ionophore γ-aminobutyric acid (GABA)-mediated Cl(-) influx antagonism...
November 12, 2016: Neuroscience
Wojciech Leppert, Jaroslaw Woron
Opioid-induced constipation (OIC) and other gastrointestinal (GI) symptoms of opioid-induced bowel dysfunction (OIBD) significantly deteriorate patients' quality of life and may lead to noncompliance with opioid schedule and undertreatment of pain. Although traditional oral laxatives are the first-line treatment of OIC, they do not address OIBD pathophysiology, and display numerous adverse effects. OIC treatment includes prokinetics (lubiprostone), opioid switch, and changing route of opioid administration...
September 2016: Therapeutic Advances in Gastroenterology
Bálint Botz, Kata Bölcskei, Zsuzsanna Helyes
Chronic inflammatory diseases and persistent pain of different origin represent common medical, social, and economic burden, and their pharmacotherapy is still an unresolved issue. Therefore, there is a great and urgent need to develop anti-inflammatory and analgesic agents with novel mechanisms of action, but it is a very challenging task. The main problem is the relatively large translational gap between the preclinical experimental data and the clinical results due to characteristics of the models, difficulties with the investigational techniques particularly for pain, as well as species differences in the mechanisms...
August 31, 2016: Wiley Interdisciplinary Reviews. Nanomedicine and Nanobiotechnology
András Váradi, Gina F Marrone, Travis C Palmer, Ankita Narayan, Márton R Szabó, Valerie Le Rouzic, Steven G Grinnell, Joan J Subrath, Evelyn Warner, Sanjay Kalra, Amanda Hunkele, Jeremy Pagirsky, Shainnel O Eans, Jessica M Medina, Jin Xu, Ying-Xian Pan, Attila Borics, Gavril W Pasternak, Jay P McLaughlin, Susruta Majumdar
Natural products found in Mitragyna speciosa, commonly known as kratom, represent diverse scaffolds (indole, indolenine, and spiro pseudoindoxyl) with opioid activity, providing opportunities to better understand opioid pharmacology. Herein, we report the pharmacology and SAR studies both in vitro and in vivo of mitragynine pseudoindoxyl (3), an oxidative rearrangement product of the corynanthe alkaloid mitragynine. 3 and its corresponding corynantheidine analogs show promise as potent analgesics with a mechanism of action that includes mu opioid receptor agonism/delta opioid receptor antagonism...
September 22, 2016: Journal of Medicinal Chemistry
Nur Izzati Ismail, Lee Ming-Tatt, Nordin Lajis, Muhammad Nadeem Akhtar, Ahmad Akira, Enoch Kumar Perimal, Daud Ahmad Israf, Mohd Roslan Sulaiman
The antinociceptive effects produced by intraperitoneal administration of a novel synthetic chalcone, 3-(2,3-dimethoxyphenyl)-1-(5-methylfuran-2-yl)prop-2-en-1-one (DMFP), were investigated in several mouse models of induced nociception. The administration of DMFP (0.1, 0.5, 1.0 and 5.0 mg/kg) produced significant attenuation on the acetic acid-induced abdominal-writhing test. It also produced a significant increase in response latency time in the hot-plate test and a marked reduction in time spent licking the injected paw in both phases of the formalin-induced paw-licking test...
2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Ari P Kirshenbaum, Jesse A Suhaka, Jessie L Phillips, Maiary Voltolini de Souza Pinto
In rats, nicotine enhances responding maintained by non-pharmacological reinforcers, and discontinuation of nicotine devalues those same reinforcers. The goal of this study was to assess the interaction of nicotine and opioid receptors and to evaluate the degree to which nicotine enhancement and nicotine-induced devaluation are related to opioid activation. Nicotine (0.4mg/kg), or nicotine plus naloxone (0.3 or 3.0mg/kg), was delivered to rats prior to progressive ratio (PR) schedule sessions in which sucrose was used as a reinforcer...
August 19, 2016: Pharmacology, Biochemistry, and Behavior
Marie Eikemo, Guro E Løseth, Tom Johnstone, Johannes Gjerstad, Frode Willoch, Siri Leknes
BACKGROUND: Rodent models highlight the key role of μ-opioid receptor (MOR) signaling in palatable food consumption. In humans, however, the effects of MOR stimulation on eating and food liking remain unclear. OBJECTIVES: Here, we tested sweet pleasantness experience in humans following MOR drug manipulations. We hypothesized that behaviors regulated by the endogenous MOR system would be enhanced by MOR agonism and decreased by antagonism. In line with rodent findings, we expected the strongest drug effects for the sweetest (high-calorie) sucrose stimuli...
October 2016: Psychopharmacology
Olga Chelnokova, Bruno Laeng, Guro Løseth, Marie Eikemo, Frode Willoch, Siri Leknes
Paying attention to others' faces and eyes is a cornerstone of human social behavior. The µ-opioid receptor (MOR) system, central to social reward-processing in rodents and primates, has been proposed to mediate the capacity for affiliative reward in humans.We assessed the role of the human MOR system in visual exploration of faces and eyes of conspecifics. Thirty healthy males received a novel, bidirectional battery of psychopharmacological treatment (a MOR agonist, a non-selective opioid antagonist, or placebo, on three separate days)...
August 16, 2016: Social Cognitive and Affective Neuroscience
Juan A Estrada, Mathew A Barlow, Darice Yoshishige, Arthur G Williams, H Fred Downey, Robert T Mallet, James L Caffrey
BACKGROUND: Intermittent hypoxia training (IHT) produces robust myocardial protection against ischemia-reperfusion induced infarction and arrhythmias. Blockade of this cardioprotection by antagonism of either β1-adrenergic or δ-opioid receptors (δ-OR) suggests autonomic and/or opioidergic adaptations. PURPOSE: To test the hypothesis that IHT shifts cardiac autonomic balance toward greater cholinergic and opioidergic influence. METHODS: Mongrel dogs completed 20d IHT, non-hypoxic sham training, or IHT with the δ-OR antagonist naltrindole (200μg/kgsc)...
July 2016: Autonomic Neuroscience: Basic & Clinical
Fu-Yan Liu, Min-Min Zhang, Ping Zeng, Wen-Wen Liu, Jing-Lei Wang, Bei Yang, Qun Dai, Jie Wei
Ghrelin has been identified as the endogenous ligand for the GHS-R1α (growth hormone secretagogue receptor 1 alpha). Our previous experiments have indicated that ghrelin (i.c.v.) induces antinociceptive effects in acute pain in mice, and the effects were mediated through the central opioid receptors and GHS-R1α. However, which opioid receptor (OR) mediates the antinociceptive effects and the molecular mechanisms are also needed to be further explored. In the present study, the antinociceptive effects of ghrelin (i...
September 2016: Peptides
Yuji Odagaki, Masakazu Kinoshita, Toshio Ota
BACKGROUND: 3(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (xanomeline) and N-desmethylclozapine are of special interest as promising antipsychotics with better efficacy, especially for negative symptoms and/or cognitive/affective impairment. METHODS: The guanosine-5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPγS) binding experiments were performed using (1) conventional filtration technique, (2) antibody-capture scintillation proximity assay, and (3) immunoprecipitation method, in brain membranes prepared from rat cerebral cortex, hippocampus, and striatum...
September 2016: Journal of Psychopharmacology
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