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Hill R, Conibear A, Dewey W, Kelly E, Henderson G. Role of Acetaldehyde in Ethanol Reversal of Tolerance to Morphine-Induced Respiratory Depression in Mice. ADVANCES IN DRUG AND ALCOHOL RESEARCH 2022; 1. [PMID: 35909497 PMCID: PMC7613180 DOI: 10.3389/adar.2021.10143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Background: Opioid users regularly consume other drugs such as alcohol (ethanol). Acute administration of ethanol rapidly reverses tolerance to morphine-induced respiratory depression. However, recent research has suggested that the primary metabolite of ethanol, acetaldehyde, may play a key role in mediating the CNS effects seen after ethanol consumption. This research investigated the role of acetaldehyde in ethanol reversal of tolerance to morphine-induced respiratory depression.Methods: Tolerance was induced in mice by 6-days implantation of a 75 mg morphine pellet with control mice implanted with a placebo pellet. Tolerance was assessed by acute morphine administration on day 6 and respiration measured by plethysmography. Levels of acetaldehyde were inhibited or enhanced by pre-treatments with the acetaldehyde chelator D-penicillamine and the inhibitor of acetaldehyde dehydrogenase disulfiram respectively.Results: Morphine pellet implanted mice displayed tolerance to an acute dose of morphine compared to placebo pellet implanted controls. Acute acetaldehyde administration dose-dependently reversed tolerance to morphine respiratory depression. As previously demonstrated, ethanol reversed morphine tolerance, and this was inhibited by D-penicillamine pre-treatment. An acute, low dose of ethanol that did not significantly reverse morphine tolerance was able to do so following disulfiram pre-treatment.Conclusion: These data suggest that acetaldehyde, the primary metabolite of ethanol, is responsible for the reversal of morphine tolerance observed following ethanol administration.
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Affiliation(s)
- Rob Hill
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
- Correspondence: Rob Hill,
| | - Alexandra Conibear
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - William Dewey
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | - Eamonn Kelly
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Graeme Henderson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
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Prolonged ethanol administration prevents the development of tolerance to morphine-induced respiratory depression. Drug Alcohol Depend 2019; 205:107674. [PMID: 31715438 DOI: 10.1016/j.drugalcdep.2019.107674] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/23/2019] [Accepted: 10/01/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Opioid users regularly consume other drugs such as alcohol (ethanol). Acute administration of ethanol can rapidly reverse tolerance to morphine-induced respiratory depression. However, alcohol consumption by opioid users is likely to occur over prolonged time periods. We have therefore sought to determine the effect of prolonged alcohol consumption on the development of tolerance to opioid respiratory depression. METHODS Mice were fed control or ethanol (5%) liquid diet for 16 days. On days 9-16 morphine tolerance was induced by administration of 3 priming injections of morphine followed by subcutaneous implantation of a morphine-filled osmotic mini-pump. Control mice received saline. Respiration was measured by plethysmography and the effect of an acute morphine challenge dose was measured on day 16 to assess the development of morphine tolerance. RESULTS Prolonged ethanol consumption for 14 days did not alter the respiratory depressant effect of an acute dose of morphine. Control mice treated with prolonged morphine developed tolerance to acute morphine respiratory depression whereas ethanol diet fed mice treated with prolonged morphine showed significant respiratory depression during morphine-pump treatment and remained sensitive to the respiratory depressant effect of the acute challenge dose of morphine. The ethanol consumption did not alter blood or brain levels of morphine, whilst conversely prolonged morphine treatment did not alter blood levels of ethanol. CONCLUSIONS Prolonged ethanol consumption prevents the development and maintenance of tolerance to the respiratory depressant effect of morphine. These data suggest that ethanol inhibition of tolerance will greatly increase the risk of fatal heroin overdose in humans.
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Hill R, Dewey WL, Kelly E, Henderson G. Oxycodone-induced tolerance to respiratory depression: reversal by ethanol, pregabalin and protein kinase C inhibition. Br J Pharmacol 2018; 175:2492-2503. [PMID: 29574756 PMCID: PMC5980627 DOI: 10.1111/bph.14219] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 03/08/2018] [Accepted: 03/13/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE Oxycodone, a prescription opioid, is a major drug of abuse, especially in the USA, and contributes significantly to opioid overdose deaths each year. Overdose deaths result primarily from respiratory depression. We have studied respiratory depression by oxycodone and have characterized how tolerance develops on prolonged exposure to the drug. We have investigated the role of PKC in maintaining tolerance and have examined whether ethanol or pregabalin reverses oxycodone-induced tolerance. EXPERIMENTAL APPROACH Respiration was measured in male CD-1 mice by whole-body plethysmography. Mice were preinjected with oxycodone then implanted with mini-pumps (s.c.) delivering 20, 45 or 120 mg·kg-1 ·day-1 oxycodone for 6 days and subsequently challenged with oxycodone (3 mg·kg-1 , i.p.) or morphine (10 mg·kg-1 , i.p.) to assess the level of tolerance. KEY RESULTS Oxycodone-treated mice developed tolerance to oxycodone and cross tolerance to morphine-induced respiratory depression. Tolerance was less with 20 mg·kg-1 ·day-1 than with 45 or 120 mg·kg-1 ·day-1 oxycodone treatment. At doses that do not depress respiration, ethanol (0.3 g·kg-1 ), pregabalin (20 mg·kg-1 ) and calphostin C (45 μg·kg-1 ) all reversed oxycodone-induced tolerance resulting in significant respiratory depression. Reversal of tolerance was less in mice treated with oxycodone (120 mg·kg-1 ·day-1 ). In mice receiving ethanol and calphostin C or ethanol and pregabalin, there was no greater reversal of tolerance than seen with either drug alone. CONCLUSION AND IMPLICATIONS These data suggest that oxycodone-induced tolerance is mediated by PKC and that reversal of tolerance by ethanol or pregabalin may be a contributory factor in oxycodone overdose deaths.
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Affiliation(s)
- Rob Hill
- School of Physiology, Pharmacology and NeuroscienceUniversity of BristolBristolBS8 1TDUK
| | - William L Dewey
- Department of Pharmacology and ToxicologyVirginia Commonwealth UniversityRichmondVA23298‐0613USA
| | - Eamonn Kelly
- School of Physiology, Pharmacology and NeuroscienceUniversity of BristolBristolBS8 1TDUK
| | - Graeme Henderson
- School of Physiology, Pharmacology and NeuroscienceUniversity of BristolBristolBS8 1TDUK
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Jacob JC, Sakakibara K, Mischel RA, Henderson G, Dewey WL, Akbarali HI. Ethanol Reversal of Oxycodone Tolerance in Dorsal Root Ganglia Neurons. Mol Pharmacol 2018; 93:417-426. [PMID: 29467238 DOI: 10.1124/mol.117.110775] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 02/08/2018] [Indexed: 01/23/2023] Open
Abstract
Oxycodone is a semisynthetic opioid compound that is widely prescribed, used, and abused today, and has a well-established role in shaping the current opioid epidemic. Previously, we have shown that tolerance develops to the antinociceptive and respiratory depressive effects of oxycodone in mice, and that a moderate dose of acute ethanol or a protein kinase C (PKC) inhibitor reversed that tolerance. To investigate further if tolerance was occurring through neuronal mechanisms, our aims for this study were to assess the effects of acute and prolonged oxycodone in isolated dorsal root ganglia (DRG) neurons and to determine if this tolerance was reversed by either ethanol or a PKC inhibitor. We found that an acute exposure to 3 μM oxycodone reduced neuronal excitability, as measured by increased threshold potentials and reduced action potential amplitude, without eliciting measurable changes in resting membrane potential. Exposure to 10 μM oxycodone for 18-24 hours prevented oxycodone's effect on neuronal excitability, indicative of tolerance development. The development of opioid tolerance was mitigated in DRG neurons from β-arrestin 2 knockout mice. Oxycodone tolerance was reversed in isolated DRG neurons by the acute application of either ethanol (20 mM) or the PKC inhibitor, bisindolylmaleimide XI hydrochloride (Bis XI), when a challenge of 3 µM oxycodone significantly reduced neuronal excitability following prolonged exposure. Through these studies, we concluded that oxycodone acutely reduced neuronal excitability, tolerance developed to this effect, and reversal of that tolerance occurred at the level of a single neuron, suggesting that reversal of oxycodone tolerance by either ethanol or Bis XI involves cellular mechanisms.
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Affiliation(s)
- Joanna C Jacob
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (J.C.J., K.S., R.A.M., W.L.D., H.I.A.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Kensuke Sakakibara
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (J.C.J., K.S., R.A.M., W.L.D., H.I.A.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Ryan A Mischel
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (J.C.J., K.S., R.A.M., W.L.D., H.I.A.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Graeme Henderson
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (J.C.J., K.S., R.A.M., W.L.D., H.I.A.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - William L Dewey
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (J.C.J., K.S., R.A.M., W.L.D., H.I.A.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Hamid I Akbarali
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (J.C.J., K.S., R.A.M., W.L.D., H.I.A.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
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Gonek M, Akbarali HI, Henderson G, Dewey WL. Reversal of oxycodone and hydrocodone tolerance by diazepam. Brain Res 2017; 1674:84-90. [PMID: 28830768 DOI: 10.1016/j.brainres.2017.08.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 08/07/2017] [Accepted: 08/14/2017] [Indexed: 02/03/2023]
Abstract
The Centers for Disease Control has declared opioid abuse to be an epidemic. Overdose deaths are largely assumed to be the result of excessive opioid consumption. In many of these cases, however, opioid abusers are often polydrug abusers. Benzodiazepines are one of the most commonly co-abused substances and pose a significant risk to opioid users. In 2016, the FDA required boxed warnings - the FDA's strongest warning - for prescription opioid analgesics and benzodiazepines about the serious risks associated with using these medications at the same time. The point of our studies was to evaluate the interactions between these two classes of drugs. We investigated whether diazepam adds to the depressant effects of opioids or do they alter the levels of tolerance to opioids. In the present study, we have found that the antinociceptive tolerance that developed to repeated administration of oxycodone was reversed by an acute dose of diazepam. Antinociceptive tolerance to hydrocodone was also reversed by acute injection of diazepam; however, a fourfold higher dose of diazepam was required when compared to reversal of oxycodone-induced tolerance. These doses of diazepam did not potentiate the acute antinociceptive effect of either opioid. The same dose of diazepam that reversed oxycodone antinociceptive tolerance also reversed oxycodone locomotor tolerance while having no potentiating effects. These studies show that diazepam does not potentiate the acute effect of prescription opioids but reverses the tolerance developed after chronic administration of the drugs.
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Affiliation(s)
- Maciej Gonek
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, 1112 East Clay Street, Richmond, VA 23298-0613, USA.
| | - Hamid I Akbarali
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, 1112 East Clay Street, Richmond, VA 23298-0613, USA
| | - Graeme Henderson
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - William L Dewey
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, 1112 East Clay Street, Richmond, VA 23298-0613, USA
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Effect of Peripheral μ-, δ-, and κ-Opioid Ligands on the Development of Tolerance to Ethanol-Induced Analgesia. Bull Exp Biol Med 2017; 163:177-179. [PMID: 28726190 DOI: 10.1007/s10517-017-3760-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Indexed: 11/27/2022]
Abstract
We studied the rate of development of tolerance to the ethanol-induced analgesia under the effect of μ-, δ-, and κ-opioid agonists and antagonists not crossing the blood-brain barrier and rapidly inactivated by gastric and duodenal proteolytic enzymes. Activation of gastric κ-opioid receptors eliminated the analgesic effect of ethanol and accelerated the development of tolerance to ethanol-induced analgesia. In contrast, activation of gastric μ-opioid receptors decelerated the development of this tolerance. Activation of gastric δ-opioid receptors produced no effect on examined tolerance. μ-Opioid receptor antagonist decelerated and δ-opioid receptor antagonist accelerated the development of tolerance to ethanol-induced analgesia. Thus, the state of gastric opioid receptors affects the manifestation of ethanol-induced analgesia and the development of tolerance to this effect.
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Jacob JC, Poklis JL, Akbarali HI, Henderson G, Dewey WL. Ethanol Reversal of Tolerance to the Antinociceptive Effects of Oxycodone and Hydrocodone. J Pharmacol Exp Ther 2017; 362:45-52. [PMID: 28442580 PMCID: PMC5454589 DOI: 10.1124/jpet.117.241083] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 04/20/2017] [Indexed: 01/09/2023] Open
Abstract
This study compared the development of tolerance to two orally bioavailable prescription opioids, oxycodone and hydrocodone, to that of morphine, and the reversal of this tolerance by ethanol. Oxycodone (s.c.) was significantly more potent in the mouse tail-withdrawal assay than either morphine or hydrocodone. Oxycodone was also significantly more potent in this assay than hydrocodone when administered orally. Tolerance was seen following chronic subcutaneous administration of each of the three drugs and by the chronic administration of oral oxycodone, but not following the chronic oral administration of hydrocodone. Ethanol (1 g/kg i.p.) significantly reversed the tolerance to the subcutaneous administration of each of the three opioids that developed when given 30 minutes prior to challenge doses. It took twice as much ethanol, when given orally, to reverse the tolerance to oxycodone. We investigated whether the observed tolerance to oxycodone and its reversal by ethanol were due to biodispositional changes or reflected a true neuronal tolerance. As expected, a relationship between brain oxycodone concentrations and activity in the tail-immersion test existed following administration of acute oral oxycodone. Following chronic treatment, brain oxycodone concentrations were significantly lower than acute concentrations. Oral ethanol (2 g/kg) reversed the tolerance to chronic oxycodone, but did not alter brain concentrations of either acute or chronic oxycodone. These studies show that there is a metabolic component of tolerance to oxycodone; however, the reversal of that tolerance by ethanol is not due to an alteration of the biodisposition of oxycodone, but rather is neuronal in nature.
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Affiliation(s)
- Joanna C Jacob
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia- (J.C.J., J.L.P., H.I.A., W.L.D.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Justin L Poklis
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia- (J.C.J., J.L.P., H.I.A., W.L.D.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Hamid I Akbarali
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia- (J.C.J., J.L.P., H.I.A., W.L.D.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - Graeme Henderson
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia- (J.C.J., J.L.P., H.I.A., W.L.D.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
| | - William L Dewey
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia- (J.C.J., J.L.P., H.I.A., W.L.D.); and School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom (G.H.)
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Pan Y, Sun X, Jiang L, Hu L, Kong H, Han Y, Qian C, Song C, Qian Y, Liu W. Metformin reduces morphine tolerance by inhibiting microglial-mediated neuroinflammation. J Neuroinflammation 2016; 13:294. [PMID: 27855689 PMCID: PMC5114746 DOI: 10.1186/s12974-016-0754-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/31/2016] [Indexed: 12/23/2022] Open
Abstract
Background Tolerance seriously impedes the application of morphine in clinical medicine. Thus, it is necessary to investigate the exact mechanisms and efficient treatment. Microglial activation and neuroinflammation in the spinal cord are thought to play pivotal roles on the genesis and maintaining of morphine tolerance. Activation of adenosine monophosphate-activated kinase (AMPK) has been associated with the inhibition of inflammatory nociception. Metformin, a biguanide class of antidiabetic drugs and activator of AMPK, has a potential anti-inflammatory effect. The present study evaluated the effects and potential mechanisms of metformin in inhibiting microglial activation and alleviating the antinociceptive tolerance of morphine. Methods The microglial cell line BV-2 cells and mouse brain-derived endothelial cell line bEnd3 cells were used. Cytokine expression was measured using quantitative polymerase chain reaction. Cell signaling was assayed by western blot and immunohistochemistry. The antinociception and morphine tolerance were assessed in CD-1 mice using tail-flick tests. Results We found that morphine-activated BV-2 cells, including the upregulation of p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation, pro-inflammatory cytokines, and Toll-like receptor-4 (TLR-4) mRNA expression, which was inhibited by metformin. Metformin suppressed morphine-induced BV-2 cells activation through increasing AMPK phosphorylation, which was reversed by the AMPK inhibitor compound C. Additionally, in BV-2 cells, morphine did not affect the cell viability and the mRNA expression of anti-inflammatory cytokines. In bEnd3 cells, morphine did not affect the mRNA expression of interleukin-1β (IL-1β), but increased IL-6 and tumor necrosis factor-α (TNF-α) mRNA expression; the effect was inhibited by metformin. Morphine also did not affect the mRNA expression of TLR-4 and chemokine ligand 2 (CCL2). Furthermore, systemic administration of metformin significantly blocked morphine-induced microglial activation in the spinal cord and then attenuated the development of chronic morphine tolerance in mice. Conclusions Metformin significantly attenuated morphine antinociceptive tolerance by suppressing morphine-induced microglial activation through increasing AMPK phosphorylation. Electronic supplementary material The online version of this article (doi:10.1186/s12974-016-0754-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yinbing Pan
- Department of Anesthesiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Xiaodi Sun
- Department of Anesthesiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Lai Jiang
- Department of Pharmacology, Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Liang Hu
- Department of Pharmacology, Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Hong Kong
- Department of Pharmacology, Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Yuan Han
- Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, People's Republic of China
| | - Cheng Qian
- Department of Pharmacology, Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Chao Song
- Department of Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, People's Republic of China
| | - Yanning Qian
- Department of Anesthesiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China
| | - Wentao Liu
- Department of Pharmacology, Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu, 210029, People's Republic of China.
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Hill R, Lyndon A, Withey S, Roberts J, Kershaw Y, MacLachlan J, Lingford-Hughes A, Kelly E, Bailey C, Hickman M, Henderson G. Ethanol Reversal of Tolerance to the Respiratory Depressant Effects of Morphine. Neuropsychopharmacology 2016; 41:762-73. [PMID: 26171718 PMCID: PMC4610039 DOI: 10.1038/npp.2015.201] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/23/2015] [Accepted: 07/01/2015] [Indexed: 11/09/2022]
Abstract
Opioids are the most common drugs associated with unintentional drug overdose. Death results from respiratory depression. Prolonged use of opioids results in the development of tolerance but the degree of tolerance is thought to vary between different effects of the drugs. Many opioid addicts regularly consume alcohol (ethanol), and post-mortem analyses of opioid overdose deaths have revealed an inverse correlation between blood morphine and ethanol levels. In the present study, we determined whether ethanol reduced tolerance to the respiratory depressant effects of opioids. Mice were treated with opioids (morphine, methadone, or buprenorphine) for up to 6 days. Respiration was measured in freely moving animals breathing 5% CO2 in air in plethysmograph chambers. Antinociception (analgesia) was measured as the latency to remove the tail from a thermal stimulus. Opioid tolerance was assessed by measuring the response to a challenge dose of morphine (10 mg/kg i.p.). Tolerance developed to the respiratory depressant effect of morphine but at a slower rate than tolerance to its antinociceptive effect. A low dose of ethanol (0.3 mg/kg) alone did not depress respiration but in prolonged morphine-treated animals respiratory depression was observed when ethanol was co-administered with the morphine challenge. Ethanol did not alter the brain levels of morphine. In contrast, in methadone- or buprenorphine-treated animals no respiratory depression was observed when ethanol was co-administered along with the morphine challenge. As heroin is converted to morphine in man, selective reversal of morphine tolerance by ethanol may be a contributory factor in heroin overdose deaths.
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Affiliation(s)
- Rob Hill
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Abi Lyndon
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Sarah Withey
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Joanne Roberts
- School of Engineering and Built Environment, Glasgow Caledonian University, Glasgow, UK
| | - Yvonne Kershaw
- School of Clinical Sciences, University of Bristol, Bristol, UK
| | - John MacLachlan
- School of Engineering and Built Environment, Glasgow Caledonian University, Glasgow, UK
| | - Anne Lingford-Hughes
- Division of Brain Sciences, Centre for Neuropsychopharmacology, Imperial College, London, UK
| | - Eamonn Kelly
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Chris Bailey
- Department of Pharmacy and Pharmacology, University of Bath, Bath, UK
| | - Matthew Hickman
- School of Social and Community Medicine, University of Bristol, Bristol, UK
| | - Graeme Henderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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Sudakov S. Development of Tolerance to Effects of Ethanol Depends on its Concentration in Stomach. ACTA ACUST UNITED AC 2016. [DOI: 10.15436/2471-061x-16-032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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Contribution of adenylyl cyclase modulation of pre- and postsynaptic GABA neurotransmission to morphine antinociception and tolerance. Neuropsychopharmacology 2014; 39:2142-52. [PMID: 24622471 PMCID: PMC4104331 DOI: 10.1038/npp.2014.62] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 03/04/2014] [Accepted: 03/11/2014] [Indexed: 01/12/2023]
Abstract
Opioid inhibition of presynaptic GABA release in the ventrolateral periaqueductal gray (vlPAG) activates the descending antinociception pathway. Tolerance to repeated opioid administration is associated with upregulation of adenylyl cyclase activity. The objective of these studies was to test the hypothesis that adenylyl cyclase contributes to opioid tolerance by modulating GABA neurotransmission. Repeated microinjections of morphine or the adenylyl cyclase activator NKH477 into the vlPAG decreased morphine antinociception as would be expected with the development of tolerance. Conversely, microinjection of the adenylyl cyclase inhibitor SQ22536 reversed both the development and expression of morphine tolerance. These behavioral results indicate that morphine tolerance is dependent on adenylyl cyclase activation. Electrophysiological experiments revealed that acute activation of adenylyl cyclase with forskolin increased the frequency of presynaptic GABA release. However, recordings from rats treated with repeated morphine administration did not exhibit increased basal miniature inhibitory postsynaptic current (mIPSC) frequency but showed a decrease in mean amplitude of mIPSCs indicating that repeated morphine administration modulates postsynaptic GABAA receptors without affecting the probability of presynaptic GABA release. SQ22536 reversed this change in mIPSC amplitude and inhibited mIPSC frequency selectively in morphine tolerant rats. Repeated morphine or NKH477 administration also decreased antinociception induced by microinjection of the GABAA receptor antagonist bicuculline, further demonstrating changes in GABA neurotransmission with morphine tolerance. These results show that the upregulation of adenylyl cyclase caused by repeated vlPAG morphine administration produces antinociceptive tolerance by modulating both pre- and postsynaptic GABA neurotransmission.
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Henderson G. The μ-opioid receptor: an electrophysiologist's perspective from the sharp end. Br J Pharmacol 2014; 172:260-7. [PMID: 24640948 DOI: 10.1111/bph.12633] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 12/02/2013] [Accepted: 12/10/2013] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED Morphine, the prototypical opioid analgesic drug, produces its behavioural effects primarily through activation of μ-opioid receptors expressed in neurones of the central and peripheral nervous systems. This perspective provides a historical view of how, over the past 40 years, the use of electrophysiological recording techniques has helped to reveal the molecular mechanisms by which acute and chronic activation of μ-opioid receptors by morphine and other opioid drugs modify neuronal function. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- Graeme Henderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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