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https://www.readbyqxmd.com/read/29677019/mu-opioid-receptors-in-nociceptive-afferents-produce-a-sustained-suppression-of-hyperalgesia-in-chronic-pain
#1
Amie Severino, Wenling Chen, Joshua K Hakimian, Brigitte L Kieffer, Claire Gaveriaux-Ruff, Wendy Walwyn, Juan Carlos Marvizon
The latent sensitization model of chronic pain reveals that recovery from some types of long-term hyperalgesia is an altered state in which nociceptive sensitization persists but is suppressed by the ongoing activity of analgesic receptors such as µ-opioid receptors (MORs). To determine whether these MORs are the ones present in nociceptive afferents, we bred mice expressing Cre-recombinase under the Nav1.8 channel promoter (Nav1.8cre) with MOR-floxed mice (flMOR). These Nav1.8cre/flMOR mice had reduced MOR expression in primary afferents, as revealed by quantitative PCR, in situ hybridization and immunofluorescence colocalization with the neuropeptide CGRP...
April 17, 2018: Pain
https://www.readbyqxmd.com/read/29582414/the-novel-%C3%AE-opioid-receptor-agonist-pzm21-depresses-respiration-and-induces-tolerance-to-antinociception
#2
Rob Hill, Alex Disney, Alex Conibear, Katy Sutcliffe, William Dewey, Stephen Husbands, Chris Bailey, Eamonn Kelly, Graeme Henderson
BACKGROUND AND PURPOSE: PZM21 is a novel μ-opioid receptor (MOPr) ligand that has been reported to induce minimal arrestin recruitment and be devoid of the respiratory depressant effects characteristic of classical μ-opioid ligands such as morphine. We have re-examined the signalling profile of PZM21 and its ability to depress respiration. EXPERIMENTAL APPROACH: G protein (Gi ) activation and arrestin-3 translocation were measured in vitro in MOPr expressing HEK 293 cells using BRET assays...
March 26, 2018: British Journal of Pharmacology
https://www.readbyqxmd.com/read/29571287/chronic-oxycodone-induces-axonal-degeneration-in-rat-brain
#3
Ruping Fan, Lisa M Schrott, Thomas Arnold, Stephen Snelling, Meghana Rao, Derrel Graham, Angela Cornelius, Nadejda L Korneeva
BACKGROUND: Chronic opioid therapy for non-malignant pain conditions has significantly increased over the last 15 years. Recently, the correlation between opioid analgesics and alternations in brain structure, such as leukoencephalopathy, axon demyelination, and white matter lesions, has been demonstrated in patients with a history of long-term use of prescription opioids. The exact mechanisms underlying the neurotoxic effect of opioids on the central nervous system are still not fully understood...
March 23, 2018: BMC Neuroscience
https://www.readbyqxmd.com/read/29530590/in-vitro-and-in-vivo-functional-profile-characterization-of-17-cyclopropylmethyl-3-14%C3%AE-dihydroxy-4-5%C3%AE-epoxy-6%C3%AE-isoquinoline-3-carboxamido-morphinan-naq-as-a-low-efficacy-mu-opioid-receptor-modulator
#4
Samuel Obeng, Yunyun Yuan, Abdulmajeed Jali, Dana E Selley, Yan Zhang
Evidence has shown that downstream signaling by mu opioid receptor (MOR) agonists that recruit β-arrestin2 may lead to the development of tolerance. Also, it has been suggested that opioid receptor desensitization and cyclic AMP overshoot contributes to the development of tolerance and occurrence of withdrawal, respectively. Therefore, studies were conducted with 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6α-(isoquinoline-3-carboxamido)morphinan (NAQ), a MOR selective partial agonist discovered in our laboratory, to characterize its effect on β-arrestin2 recruitment and precipitation of a cyclic AMP overshoot...
March 9, 2018: European Journal of Pharmacology
https://www.readbyqxmd.com/read/29465323/peripheral-mu-opioid-receptors-attenuate-the-responses-of-group-iii-and-iv-afferents-to-contraction-in-rats-with-simulated-peripheral-artery-disease
#5
Jonathan E Harms, Audrey J Stone, Marc P Kaufman
Patients with peripheral artery disease show an exaggerated pressor response to mild exercise, an effect attributable to the exercise pressor reflex, whose afferent arm is comprised of the thinly myelinated group III and unmyelinated group IV afferents. Previously, we found that DAMGO, a μ opioid agonist injected into the femoral artery, attenuated the exaggerated exercise pressor reflex in rats with ligated femoral arteries, a preparation which simulates the blood flow patterns to muscle that is seen in patients with PAD...
February 21, 2018: Journal of Neurophysiology
https://www.readbyqxmd.com/read/29459641/therapeutic-effects-of-diclofenac-pregabalin-and-duloxetine-on-disuse-induced-chronic-musculoskeletal-pain-in-rats
#6
Yusuke Ohmichi, Mika Ohmichi, Nobuhito Murai, Masaya Yasui, Nobuaki Takeshita, Hidehiro Oshibuchi, Munekazu Naito, Takashi Nakano, Jun Sato
The aim of this study was to clarify the mechanism of disuse-induced muscle hyperalgesia through the evaluation of the pharmacological behaviour of muscle hyperalgesia profiles in chronic post-cast pain (CPCP) rats with acute and chronic-phase mirror-image muscle hyperalgesia treated with diclofenac (NSAID), pregabalin (an inhibitor of Ca2+ channel α2δ), and duloxetine (SNRI). After 2 weeks of cast immobilization, the peak cross-sectional area and muscle wet weight of the ipsilateral soleus and gastrocnemius muscles decreased more significantly in CPCP rats than in untreated rats...
February 19, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29447951/suction-electrode-recording-in-locus-coeruleus-of-newborn-rat-brain-slices-reveals-network-bursting-comprising-summated-non-synchronous-spiking
#7
Vladimir Rancic, Bijal Rawal, Bogdan Panaitescu, Araya Ruangkittisakul, Klaus Ballanyi
The brainstem locus coeruleus (LC) controling behaviors like arousal, sleep, breathing, pain or opioid withdrawal is an established model for spontaneous action potential synchronization. Such synchronous 'spiking' might produce an extracellular field potential (FP) which is a crucial tool for neural network analyses. We found using ≥10 μm tip diameter suction electrodes in newborn rat brainstem slices that the LC generates at ∼1 Hz a robust rhythmic FP (rFP). During distinct rFP phases, LC neurons discharge with a jitter of ±33 ms single spikes that summate to a ∼200 ms-lasting population burst...
February 12, 2018: Neuroscience Letters
https://www.readbyqxmd.com/read/29447132/role-of-gpcr-mu-opioid-receptor-tyrosine-kinase-epidermal-growth-factor-crosstalk-in-opioid-induced-hyperalgesic-priming-type-ii
#8
Dionéia Araldi, Luiz F Ferrari, Jon D Levine
Repeated stimulation of mu-opioid receptors (MORs), by an MOR-selective agonist DAMGO induces type II priming, a form of nociceptor neuroplasticity, which has 2 components: opioid-induced hyperalgesia (OIH) and prolongation of prostaglandin-E2 (PGE2)-induced hyperalgesia. We report that intrathecal antisense knockdown of the MOR in nociceptors, prevented the induction of both components of type II priming. Type II priming was also eliminated by SSP-saporin, which destroys the peptidergic class of nociceptors...
January 11, 2018: Pain
https://www.readbyqxmd.com/read/29341826/mu-opioid-receptors-inhibit-the-exercise-pressor-reflex-by-closing-n-type-calcium-channels-but-not-by-opening-girk-channels-in-rats
#9
Juan A Estrada, Marc P Kaufman
Mu opioid G-protein coupled receptors (MOR) interact with ion channels to decrease neuronal excitability. In humans, intrathecal administration of the MOR agonist, fentanyl, inhibits the exercise pressor reflex, an effect that can be attributed to either the opening of inward rectifying potassium channels (GIRK) or the closing of N-type calcium channels. The purpose of this study was to determine if the highly selective MOR agonist DAMGO attenuates the exercise pressor reflex, and which of these two channels are responsible for this effect...
January 17, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29259544/dichotomous-effects-of-mu-opioid-receptor-activation-on-striatal-low-threshold-spike-interneurons
#10
Rasha Elghaba, Enrico Bracci
Striatal low-threshold spike interneurons (LTSIs) are tonically active neurons that express GABA and nitric oxide synthase and are involved in information processing as well as neurovascular coupling. While mu opioid receptors (MORs) and their ligand encephalin are prominent in the striatum, their action on LTSIs has not been investigated. We addressed this issue carrying out whole-cell recordings in transgenic mice in which the NPY-expressing neurons are marked with green fluorescent protein (GFP). The MOR agonist (D-Ala(2), N-MePhe(4), Gly-ol)-enkephalin (DAMGO) produced dual effects on subpopulations of LTSIs...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/29237725/abin-1-negatively-regulates-%C3%AE-opioid-receptor-function
#11
Peilan Zhou, Jiebing Jiang, Hui Yan, Yulei Li, Junru Zhao, Xiao Wang, Ruibin Su, Zehui Gong
The μ -opioid receptor (MOR) is a Gi/o protein-coupled receptor that mediates analgesic, euphoric, and reward effects. Using a bacterial two-hybrid screen, we reported that the carboxyl tail of the rat MOR associates with A20-binding inhibitor of nuclear factor κ B (ABIN-1). This interaction was confirmed by direct protein-protein binding and coimmunoprecipitation of MOR and ABIN-1 proteins in cell lysates. Saturation binding studies showed that ABIN-1 had no effect on MOR binding. However, the interaction of ABIN-1 and MOR inhibited the activation of G proteins induced by DAMGO ([d-Ala2,N-Me-Phe4,Gly5-ol]-Enkephalin)...
February 2018: Molecular Pharmacology
https://www.readbyqxmd.com/read/29042318/mechanisms-of-%C3%AE-opioid-receptor-inhibition-of-nmda-receptor-induced-substance-p-release-in-the-rat-spinal-cord
#12
Wenling Chen, Helena S Ennes, James A McRoberts, Juan Carlos Marvizón
The interaction between NMDA receptors and μ-opioid receptors in primary afferent terminals was studied by using NMDA to induce substance P release, measured as neurokinin 1 receptor internalization. In rat spinal cord slices, the μ-opioid receptor agonists morphine, DAMGO and endomorphin-2 inhibited NMDA-induced substance P release, whereas the antagonist CTAP right-shifted the concentration response of DAMGO. In vivo, substance P release induced by intrathecal NMDA after priming with BDNF was inhibited by DAMGO...
January 2018: Neuropharmacology
https://www.readbyqxmd.com/read/29035918/dopaminergic-mechanisms-in-periaqueductal-gray-mediated-antinociception
#13
Glaucia Tobaldini, Rafael A Reis, Natalia F Sardi, Mayla K Lazzarim, Dabna H Tomim, Marcelo M S Lima, Luana Fischer
As important as perceiving pain is the ability to modulate this perception in some contextual salient situations. The periaqueductal gray (PAG) is perhaps the most important site of endogenous pain modulation; however, little is known about dopaminergic mechanisms underlying PAG-mediated antinociception. In this study, we used a pharmacological approach to evaluate this subject. We found that µ-opioid receptor-induced antinociception (DAMGO, 0.3 μg) from PAG was blocked by the coadministration of either D1-like or D2-like dopaminergic antagonists (SCH23390, 2, 4, and 6 μg or raclopride, 2 and 4 μg, respectively) both in the tail-flick and in the mechanical paw-withdrawal test...
October 13, 2017: Behavioural Pharmacology
https://www.readbyqxmd.com/read/28951361/-%C3%A2%C2%B5-opioid-receptors-in-the-central-nucleus-of-the-amygdala-mediate-sodium-intake-in-rats
#14
Jun-Bao Yan, Zhi-Hong Hu
OBJECTIVE: To investigate the opioidergic mechanism of the central nucleus of the amygdala (CeA) for regulating sodium appetite in rats. METHDOS: Using the elaborate invasive cerebral cannulation and brain microinjection method, we observed the effects of bilateral intra-CeA injections of DAMGO (a selective µ-opioid receptor agonist) and CTAP (a highly selective µ-opioid receptor antagonist), either alone or in combination, on NaCl solution (0.3 mol/L) and water intake by rats in different models of Na(+) ingestion...
September 20, 2017: Nan Fang Yi Ke da Xue Xue Bao, Journal of Southern Medical University
https://www.readbyqxmd.com/read/28864212/14-o-methylmorphine-a-novel-selective-mu-opioid-receptor-agonist-with-high-efficacy-and-affinity
#15
Ferenc Zádor, Mihály Balogh, András Váradi, Zoltán S Zádori, Kornél Király, Edina Szűcs, Bence Varga, Bernadette Lázár, Sándor Hosztafi, Pál Riba, Sándor Benyhe, Susanna Fürst, Mahmoud Al-Khrasani
14-O-methyl (14-O-Me) group in morphine-6-O-sulfate (M6SU) or oxymorphone has been reported to be essential for enhanced affinity, potency and antinociceptive effect of these opioids. Herein we report on the pharmacological properties (potency, affinity and efficacy) of the new compound, 14-O-methylmorphine (14-O-MeM) in in vitro. Additionally, we also investigated the antinociceptive effect of the novel compound, as well as its inhibitory action on gastrointestinal transit in in vivo. The potency and efficacy of test compound were measured by [ 35 S]GTPγS binding, isolated mouse vas deferens (MVD) and rat vas deferens (RVD) assays...
November 5, 2017: European Journal of Pharmacology
https://www.readbyqxmd.com/read/28839004/ventilation-and-neurochemical-changes-during-%C3%A2%C2%B5-opioid-receptor-activation-or-blockade-of-excitatory-receptors-in-the-hypoglossal-motor-nucleus-of-goats
#16
Thomas M Langer, Suzanne E Neumueller, Emma Crumley, Nicholas J Burgraff, Sawan Talwar, Matthew R Hodges, Lawrence Pan, Hubert V Forster
Neuromodulator interdependence posits that changes in one or more neuromodulators are compensated by changes in other modulators to maintain stability in the respiratory control network. Herein, we studied compensatory neuromodulation in the hypoglossal motor nucleus (HMN) after chronic implantation of microtubules unilaterally ( n = 5) or bilaterally ( n = 5) into the HMN. After recovery, receptor agonists or antagonists in mock cerebrospinal fluid (mCSF) were dialyzed during the awake and non-rapid eye movement (NREM) sleep states...
December 1, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28836121/nerve-decompression-improves-spinal-synaptic-plasticity-of-opioid-receptors-for-pain-relief
#17
To-Jung Tseng, Ming-Ling Yang, Yu-Lin Hsieh, Miau-Hwa Ko, Sung-Tsang Hsieh
Nerve decompression is an essential therapeutic strategy for pain relief clinically; however, its potential mechanism remains poorly understood. Opioid analgesics acting on opioid receptors (OR) within the various regions of the nervous system have been used widely for pain management. We therefore hypothesized that nerve decompression in a neuropathic pain model of chronic constriction injury (CCI) improves the synaptic OR plasticity in the dorsal horn, which is in response to alleviate pain hypersensitivity...
February 2018: Neurotoxicity Research
https://www.readbyqxmd.com/read/28815604/chronic-morphine-reduces-the-readily-releasable-pool-of-gaba-a-presynaptic-mechanism-of-opioid-tolerance
#18
Adrianne R Wilson-Poe, Hyo-Jin Jeong, Christopher W Vaughan
KEY POINTS: Chronic treatment with opioids, such as morphine, leads to analgesic tolerance. While postsynaptic opioid tolerance is well documented, the involvement of presynaptic mechanisms remains unclear. We show that chronic morphine reduces the ability of periaqueductal grey (PAG) neurons to maintain GABAergic transmission. This depression of GABAergic transmission was due to a reduction in the effective size of the readily releasable pool. This also led to a reduction in opioid presynaptic inhibition; these presynaptic adaptations need to be considered in the development of strategies to reduce opioid tolerance...
October 15, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28654029/measuring-g-protein-coupled-receptor-signaling-via-radio-labeled-gtp-binding
#19
Chirag Vasavda, Nicholas W Zaccor, Paul C Scherer, Charlotte J Sumner, Solomon H Snyder
G-Protein-Coupled Receptors (GPCRs) are a large family of transmembrane receptors that play critical roles in normal cellular physiology and constitute a major pharmacological target for multiple indications, including analgesia, blood pressure regulation, and the treatment of psychiatric disease. Upon ligand binding, GPCRs catalyze the activation of intracellular G-proteins by stimulating the incorporation of guanosine triphosphate (GTP). Activated G-proteins then stimulate signaling pathways that elicit cellular responses...
June 9, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28645621/two-delta-opioid-receptor-subtypes-are-functional-in-single-ventral-tegmental-area-neurons-and-can-interact-with-the-mu-opioid-receptor
#20
Elyssa B Margolis, Wakako Fujita, Lakshmi A Devi, Howard L Fields
The mu and delta opioid receptors (MOR and DOR) are highly homologous members of the opioid family of GPCRs. There is evidence that MOR and DOR interact, however the extent to which these interactions occur in vivo and affect synaptic function is unknown. There are two stable DOR subtypes: DPDPE sensitive (DOR1) and deltorphin II sensitive (DOR2); both agonists are blocked by DOR selective antagonists. Robust motivational effects are produced by local actions of both MOR and DOR ligands in the ventral tegmental area (VTA)...
September 1, 2017: Neuropharmacology
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