1
|
Gerra MC, Carnevali D, Pedersen IS, Donnini C, Manfredini M, González-Villar A, Triñanes Y, Pidal-Miranda M, Arendt-Nielsen L, Carrillo-de-la-Peña MT. DNA methylation changes in genes involved in inflammation and depression in fibromyalgia: a pilot study. Scand J Pain 2020; 21:372-383. [PMID: 34387961 DOI: 10.1515/sjpain-2020-0124] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/05/2020] [Indexed: 12/15/2022]
Abstract
OBJECTIVES The present pilot study aims to investigate DNA methylation changes of genes related to fibromyalgia (FM) development and its main comorbid symptoms, including sleep impairment, inflammation, depression and other psychiatric disorders. Epigenetic modifications might trigger or perpetuate complex interplay between pain transduction/transmission, central pain processing and experienced stressors in vulnerable individuals. METHODS We conducted DNA methylation analysis by targeted bisulfite NGS sequencing testing differential methylation in 112 genomic regions from leukocytes of eight women with FM and their eight healthy sisters as controls. RESULTS Tests for differentially methylated regions and cytosines brought focus on the GRM2 gene, encoding the metabotropic glutamate receptor2. The slightly increased DNA methylation observed in the GRM2 region of FM patients may confirm the involvement of the glutamate pathway in this pathological condition. Logistic regression highlighted the simultaneous association of methylation levels of depression and inflammation-related genes with FM. CONCLUSIONS Altogether, the results evidence the glutamate pathway involvement in FM and support the idea that a combination of methylated and unmethylated genes could represent a risk factor to FM or its consequence, more than single genes. Further studies on the identified biomarkers could contribute to unravel the causative underlying FM mechanisms, giving reliable directions to research, improving the diagnosis and effective therapies.
Collapse
Affiliation(s)
- Maria Carla Gerra
- Department of Health Science and Technology, Center for Neuroplasticity and Pain (CNAP), SMI®, Aalborg University, Aalborg, Denmark
| | - Davide Carnevali
- Department of Chemistry, Life Sciences, and Environmental Sustainability, University of Parma (UNIPR), Parma, Italy
| | - Inge Søkilde Pedersen
- Department of Clinical Medicine, Aalborg University Hospital and Aalborg University, Molecular Diagnostics, Aalborg, Denmark
| | - Claudia Donnini
- Department of Chemistry, Life Sciences, and Environmental Sustainability, University of Parma (UNIPR), Parma, Italy
| | - Matteo Manfredini
- Department of Chemistry, Life Sciences, and Environmental Sustainability, University of Parma (UNIPR), Parma, Italy
| | - Alberto González-Villar
- Department of Clinical Psychology and Psychobiology, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Yolanda Triñanes
- Department of Clinical Psychology and Psychobiology, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Marina Pidal-Miranda
- Department of Clinical Psychology and Psychobiology, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Lars Arendt-Nielsen
- Department of Health Science and Technology, Center for Neuroplasticity and Pain (CNAP), SMI®, Aalborg University, Aalborg, Denmark
| | | |
Collapse
|
2
|
Fung T, Asiri YI, Taheri K, Wall R, Schwarz SKW, Puil E, MacLeod BA. Antinociception by intrathecal delivery of the novel non-opioid 1-amino-1-cyclobutanecarboxylic acid. Eur J Pain 2018; 23:260-271. [PMID: 30091274 DOI: 10.1002/ejp.1301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 08/02/2018] [Accepted: 08/03/2018] [Indexed: 11/11/2022]
Abstract
BACKGROUND Neuraxial opioids are widely used for intraoperative and post-operative analgesia. The risk of severe adverse effects including respiratory depression accompanies this analgesia, prompting the need for effective non-opioid alternatives. Systemic 1-amino-1-cyclobutanecarboxylic acid showed promise in preliminary studies to produce antinociception without observable toxicity. However, the effects of 1-amino-1-cyclobutanecarboxylic acid after intrathecal administration are unknown. The aim of this study was to determine whether intrathecal administration of 1-amino-1-cyclobutanecarboxylic acid produces antinociceptive effects in murine models and to elucidate its site and receptor mechanism of action. METHODS Female CD-1 mice were randomized to receive intrathecal, intraperitoneal and intraplantar injections of 1-amino-1-cyclobutanecarboxylic acid. Animals receiving intrathecal injections were anaesthetized and injected between L5 and L6. Animals then received an intraplantar injection of 10% hypertonic saline into the right hindpaw and were video-recorded for 30 min. Videos were analyzed by a blinded observer who determined the duration that animals exhibited nocifensive responses. RESULTS Intrathecal or intraperitoneal administration of 1-amino-1-cyclobutanecarboxylic acid reduced the time that animals exhibited nocifensive behaviour, whereas intraplantar administration produced no effect. The effects of intrathecal 1-amino-1-cyclobutanecarboxylic acid were restricted in dermatomal distribution, reversible and produced little or no depression of respiratory rate. An NMDA antagonist blocked antinociception, while mu-opioid or GABAB antagonists did not prevent ACBC antinociception. CONCLUSIONS Intrathecal 1-amino-1-cyclobutanecarboxylic acid in mice produces robust, brief antinociceptive effects with a dermatomal distribution corresponding to the lumbar site of administration. This amino acid merits further exploration as a non-opioid neuraxial analgesic with little or no respiratory side effects. SIGNIFICANCE The novel, non-opioid analgesic, 1-amino-1-cyclobutanecarboxylic acid, produced robust, reversible and localized antinociception in murine models of pain. This study provides evidence supporting further investigation and development of 1-amino-1-cyclobutanecarboxylic acid as a non-opioid spinal analgesic.
Collapse
Affiliation(s)
- Timothy Fung
- Hugill Anesthesia Research Centre, Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Yahya I Asiri
- Hugill Anesthesia Research Centre, Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Kamyar Taheri
- Cannevert Therapeutics Ltd, Vancouver, British Columbia, Canada
| | - Richard Wall
- Hugill Anesthesia Research Centre, Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Stephan K W Schwarz
- Hugill Anesthesia Research Centre, Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada.,Department of Anesthesia, Providence Health Care/St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Ernest Puil
- Hugill Anesthesia Research Centre, Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Bernard A MacLeod
- Hugill Anesthesia Research Centre, Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
3
|
Asiri YI, Fung T, Schwarz SKW, Asseri KA, Welch ID, Schuppli CA, Barr AM, Wall RA, Puil E, MacLeod BA. An Intraplantar Hypertonic Saline Assay in Mice for Rapid Screening of Analgesics. Anesth Analg 2018; 127:548-555. [DOI: 10.1213/ane.0000000000002525] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
4
|
Sheahan TD, Valtcheva MV, McIlvried LA, Pullen MY, Baranger DA, Gereau RW. Metabotropic Glutamate Receptor 2/3 (mGluR2/3) Activation Suppresses TRPV1 Sensitization in Mouse, But Not Human, Sensory Neurons. eNeuro 2018; 5:ENEURO.0412-17.2018. [PMID: 29662945 PMCID: PMC5898698 DOI: 10.1523/eneuro.0412-17.2018] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 02/06/2018] [Accepted: 02/07/2018] [Indexed: 01/08/2023] Open
Abstract
The use of human tissue to validate putative analgesic targets identified in rodents is a promising strategy for improving the historically poor translational record of preclinical pain research. We recently demonstrated that in mouse and human sensory neurons, agonists for metabotropic glutamate receptors 2 and 3 (mGluR2/3) reduce membrane hyperexcitability produced by the inflammatory mediator prostaglandin E2 (PGE2). Previous rodent studies indicate that mGluR2/3 can also reduce peripheral sensitization by suppressing inflammation-induced sensitization of TRPV1. Whether this observation similarly translates to human sensory neurons has not yet been tested. We found that activation of mGluR2/3 with the agonist APDC suppressed PGE2-induced sensitization of TRPV1 in mouse, but not human, sensory neurons. We also evaluated sensory neuron expression of the gene transcripts for mGluR2 (Grm2), mGluR3 (Grm3), and TRPV1 (Trpv1). The majority of Trpv1+ mouse and human sensory neurons expressed Grm2 and/or Grm3, and in both mice and humans, Grm2 was expressed in a greater percentage of sensory neurons than Grm3. Although we demonstrated a functional difference in the modulation of TRPV1 sensitization by mGluR2/3 activation between mouse and human, there were no species differences in the gene transcript colocalization of mGluR2 or mGluR3 with TRPV1 that might explain this functional difference. Taken together with our previous work, these results suggest that mGluR2/3 activation suppresses only some aspects of human sensory neuron sensitization caused by PGE2. These differences have implications for potential healthy human voluntary studies or clinical trials evaluating the analgesic efficacy of mGluR2/3 agonists or positive allosteric modulators.
Collapse
Affiliation(s)
- Tayler D. Sheahan
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
- Washington University Program in Neuroscience, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Manouela V. Valtcheva
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
- Washington University Program in Neuroscience, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Lisa A. McIlvried
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Melanie Y. Pullen
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - David A.A. Baranger
- Washington University Program in Neuroscience, Washington University School of Medicine, St. Louis, Missouri 63110
- BRAIN Laboratory, Department of Psychological and Brain Sciences, Washington University in St. Louis, St. Louis, Missouri 63130
| | - Robert W. Gereau
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| |
Collapse
|
5
|
Notartomaso S, Mascio G, Bernabucci M, Zappulla C, Scarselli P, Cannella M, Imbriglio T, Gradini R, Battaglia G, Bruno V, Nicoletti F. Analgesia induced by the epigenetic drug, L-acetylcarnitine, outlasts the end of treatment in mouse models of chronic inflammatory and neuropathic pain. Mol Pain 2017; 13:1744806917697009. [PMID: 28326943 PMCID: PMC5407675 DOI: 10.1177/1744806917697009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Background L-acetylcarnitine, a drug marketed for the treatment of chronic pain, causes analgesia by epigenetically up-regulating type-2 metabotropic glutamate (mGlu2) receptors in the spinal cord. Because the epigenetic mechanisms are typically long-lasting, we hypothesized that analgesia could outlast the duration of L-acetylcarnitine treatment in models of inflammatory and neuropathic pain. Results A seven-day treatment with L-acetylcarnitine (100 mg/kg, once a day, i.p.) produced an antiallodynic effect in the complete Freund adjuvant mouse model of chronic inflammatory pain. L-Acetylcarnitine-induced analgesia persisted for at least 14 days after drug withdrawal. In contrast, the analgesic effect of pregabalin, amitryptiline, ceftriaxone, and N-acetylcysteine disappeared seven days after drug withdrawal. L-acetylcarnitine treatment enhanced mGlu2/3 receptor protein levels in the dorsal region of the spinal cord. This effect also persisted for two weeks after drug withdrawal and was associated with increased levels of acetylated histone H3 bound to the Grm2 gene promoter in the dorsal root ganglia. A long-lasting analgesic effect of L-acetylcarnitine was also observed in mice subjected to chronic constriction injury of the sciatic nerve. In these animals, a 14-day treatment with pregabalin, amitryptiline, tramadol, or L-acetylcarnitine produced a significant antiallodynic effect, with pregabalin displaying the greatest efficacy. In mice treated with pregabalin, tramadol or L-acetylcarnitine the analgesic effect was still visible 15 days after the end of drug treatment. However, only in mice treated with L-acetylcarnitine analgesia persisted 37 days after drug withdrawal. This effect was associated with an increase in mGlu2/3 receptor protein levels in the dorsal horns of the spinal cord. Conclusions Our findings suggest that L-acetylcarnitine has the unique property to cause a long-lasting analgesic effect that might reduce relapses in patients suffering from chronic pain.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | - Roberto Gradini
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,2 Department of Experimental Medicine, Sapienza University, Rome, Italy
| | | | - Valeria Bruno
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,3 Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - Ferdinando Nicoletti
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,3 Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| |
Collapse
|
6
|
Fung T, Asiri YI, Wall R, Schwarz SKW, Puil E, MacLeod BA. Variations of isovaline structure related to activity in the formalin foot assay in mice. Amino Acids 2017; 49:1203-1213. [PMID: 28432424 DOI: 10.1007/s00726-017-2421-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 04/10/2017] [Indexed: 01/25/2023]
Abstract
Current centrally acting analgesics such as opioids are associated with adverse effects that limit their use and threaten patient safety. Isovaline is a novel prototype analgesic that produces peripheral antinociception in several pain models with little or no effect on the central nervous system. The aim of this study was to establish a preliminary structure-activity relationship for isovaline derivatives by assaying efficacy in the formalin foot assay and central adverse effect profile in mice. Selected compounds were tested using the formalin foot assay to determine efficacy in reducing formalin-induced behaviors. Of the compounds tested, R-isovaline, S-isovaline, and 1-amino-1-cyclobutanecarboxylic acid reduced nocifensive behavior in phase II of the assay. These effects occurred without affecting performance on the rotarod, indicating that the reduction in nocifensive behaviors was not due to sedation or motor incoordination. Modifications to isovaline that increased its steric size without a cyclobutane ring formation produced compounds with no activity in the formalin foot assay. These findings indicate that the conformational stability of isovaline or the ability to form a cyclobutane ring is necessary for activity in the formalin foot assay.
Collapse
Affiliation(s)
- Timothy Fung
- Department of Anesthesiology, Pharmacology & Therapeutics, Hugill Anesthesia Research Centre, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Yahya I Asiri
- Department of Anesthesiology, Pharmacology & Therapeutics, Hugill Anesthesia Research Centre, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Richard Wall
- Department of Anesthesiology, Pharmacology & Therapeutics, Hugill Anesthesia Research Centre, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Stephan K W Schwarz
- Department of Anesthesiology, Pharmacology & Therapeutics, Hugill Anesthesia Research Centre, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.,Department of Anesthesia, Providence Health Care/St. Paul's Hospital, Vancouver, BC, V6Z 1Y6, Canada
| | - Ernest Puil
- Department of Anesthesiology, Pharmacology & Therapeutics, Hugill Anesthesia Research Centre, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Bernard A MacLeod
- Department of Anesthesiology, Pharmacology & Therapeutics, Hugill Anesthesia Research Centre, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.
| |
Collapse
|
7
|
Differential effects of R-isovaline and the GABA B agonist, baclofen, in the guinea pig ileum. Eur J Pharmacol 2016; 791:85-90. [PMID: 27521870 DOI: 10.1016/j.ejphar.2016.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 08/02/2016] [Accepted: 08/03/2016] [Indexed: 11/22/2022]
Abstract
R-isovaline is a non-proteinogenic amino acid which produces analgesia in a range of nociceptive assays. Mediation of this effect by metabotropic receptors for γ-aminobutyric acid (GABA) and glutamate, demonstrated by previous work, may depend on the type of tissue or receptor system. The objective of this study was to assess the activity of R-isovaline acting at GABAB and group II metabotropic glutamate receptors in guinea pig ileum, which is known to exhibit well-defined responses to GABAB agonists such as baclofen. The effects of bath-applied R-isovaline and RS-baclofen were examined on electrically evoked contractions of guinea pig ileum and during GABAB antagonism by CGP52432. In separate experiments, the group II metabotropic glutamate receptor agonist, LY354740 was applied to determine the functional presence of these receptors. R-isovaline (1-100mM) decreased the amplitude of ileal muscle contractions and increased tension. RS-baclofen reduced contraction amplitude, but decreased tension. CGP52432 did not prevent the effects of R-isovaline on contraction amplitude, but antagonized effects of RS-baclofen on contraction amplitude. The group II metabotropic glutamate receptor agonist, LY354740, produced no detectable effects on evoked contractions. R-isovaline differed significantly from RS-baclofen in its actions in the guinea pig ileum, indicated in particular by the finding that CGP52432 blocked only the effects of RS-baclofen. The ileal tissue did not respond to a group II metabotropic glutamate receptor agonist, previously shown to co-mediate R-isovaline analgesia. These findings raise the possibility of a novel therapeutic target at unknown receptors for R-isovaline-like compounds in the guinea pig ileum.
Collapse
|
8
|
Kirkpatrick DR, McEntire DM, Smith TA, Dueck NP, Kerfeld MJ, Hambsch ZJ, Nelson TJ, Reisbig MD, Agrawal DK. Transmission pathways and mediators as the basis for clinical pharmacology of pain. Expert Rev Clin Pharmacol 2016; 9:1363-1387. [PMID: 27322358 PMCID: PMC5215101 DOI: 10.1080/17512433.2016.1204231] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
INTRODUCTION Mediators in pain transmission are the targets of a multitude of different analgesic pharmaceuticals. This review explores the most significant mediators of pain transmission as well as the pharmaceuticals that act on them. Areas covered: The review explores many of the key mediators of pain transmission. In doing so, this review uncovers important areas for further research. It also highlights agents with potential for producing novel analgesics, probes important interactions between pain transmission pathways that could contribute to synergistic analgesia, and emphasizes transmission factors that participate in transforming acute injury into chronic pain. Expert commentary: This review examines current pain research, particularly in the context of identifying novel analgesics, highlighting interactions between analgesic transmission pathways, and discussing factors that may contribute to the development of chronic pain after an acute injury.
Collapse
Affiliation(s)
- Daniel R. Kirkpatrick
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Dan M. McEntire
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Tyler A. Smith
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Nicholas P. Dueck
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Mitchell J. Kerfeld
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Zakary J. Hambsch
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Taylor J. Nelson
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Mark D. Reisbig
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| | - Devendra K. Agrawal
- Departments of Clinical and Translational Science and Anesthesiology, Creighton University School of Medicine, Omaha, NE 68178 USA
| |
Collapse
|
9
|
Whitehead RA, Schwarz SKW, Asiri YI, Fung T, Puil E, MacLeod BA. The Efficacy and Safety of the Novel Peripheral Analgesic Isovaline as an Adjuvant to Propofol for General Anesthesia and Conscious Sedation: A Proof-of-Principle Study in Mice. Anesth Analg 2016; 121:1481-7. [PMID: 26579656 DOI: 10.1213/ane.0000000000000996] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The combination of propofol and an opioid analgesic is widely used for procedural sedation, as well as total IV anesthesia. However, opioids produce respiratory depression, a primary cause of death due to these agents. We recently reported on the antinociceptive actions of isovaline, a small nonbiogenic amino acid that does not readily cross the blood-brain barrier and acts on peripheral γ-aminobutyric acid type B receptors. Here, we explored the possibility that isovaline may be an effective and safe alternative to opioids as an adjunct to propofol for producing anesthesia. METHODS With approval from our Animal Care Committee, we conducted an in vivo study in adult female CD-1 mice using Dixon's "up-and-down" method for dose assessment. Animals received intraperitoneal saline, propofol, isovaline, fentanyl, or coadministration of propofol with isovaline or fentanyl. We assessed hypnosis by a loss of righting reflex and immobility by an absence of motor response to tail clip application. General anesthesia was defined as the presence of both hypnosis and immobility. We assessed conscious sedation as a decrease in time on a rotarod. The maximal dose without respiratory rates of <4 per minute, apnea, or death was defined as the maximal tolerated dose. RESULTS Either isovaline or fentanyl coadministered with propofol at its half-maximal effective dose (ED50) for hypnosis produced general anesthesia (isovaline ED50, 96 mg/kg [95% confidence interval {CI}, 88-124 mg/kg]; fentanyl ED50, 0.12 mg/kg [95% CI, 0.08-3.5 mg/kg]). Propofol produced hypnosis (ED50, 124 mg/kg [95% CI, 84-3520 mg/kg]) but did not block responses to tail clip application. Neither isovaline nor fentanyl produced hypnosis at doses which produced immobility (isovaline ED50, 350 mg/kg [95% CI, 286-1120 mg/kg]; fentanyl ED50, 0.35 mg/kg [95% CI, 0.23-0.51 mg/kg]). Isovaline at its analgesic ED50, coadministered with a subhypnotic dose of propofol (40 mg/kg), did not exacerbate propofol-induced deficits in rotarod performance. The median maximal tolerated dose of fentanyl coadministered with the hypnotic ED50 of propofol was 11 mg/kg (95% CI, 8-18 mg/kg). Isovaline at a maximal deliverable (soluble) dose of 5000 mg/kg produced no apparent respiratory depression or other adverse effects. CONCLUSIONS The novel analgesic, isovaline, coadministered with propofol, produced general anesthesia and conscious sedation in mice. The margin of safety for propofol-isovaline was considerably higher than that for propofol-fentanyl. This study's results show that propofol-based sedation and general anesthesia can be effectively and safely produced by replacing the conventional opioid component with a brain-impermeant peripherally acting γ-aminobutyric acid type B receptor agonist. The results provide proof of the principle of combining a peripheral analgesic with a centrally acting hypnotic to produce general anesthesia. This principle suggests a novel approach to clinical general anesthesia and conscious sedation.
Collapse
Affiliation(s)
- Ryan A Whitehead
- From the *Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada; and †Department of Anesthesia, St. Paul's Hospital, Vancouver, British Columbia, Canada
| | | | | | | | | | | |
Collapse
|