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Back S, Kroon E, Colyer-Patel K, Cousijn J. Does nitrous oxide addiction exist? An evaluation of the evidence for the presence and prevalence of substance use disorder symptoms in recreational nitrous oxide users. Addiction 2024; 119:609-618. [PMID: 37904333 DOI: 10.1111/add.16380] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 10/03/2023] [Indexed: 11/01/2023]
Abstract
BACKGROUND Prevalence of nitrous oxide (N2 O) use appears to be increasing in numerous countries worldwide, and excessive use has been associated with physical and mental problems. Because there currently is no consensus whether N2 O has addictive potential, we aimed to evaluate the evidence for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in N2 O users. ANALYSIS A literature search was conducted to assess the evidence for the presence of any of the 11 DSM-5 SUD symptoms in N2 O users and the prevalence experiencing those symptoms. A substantial part of the studied N2 O users use more than intended (i.e. 46% to 98%) and spend a substantial amount of time using N2 O. At least some of the studied N2 O users experience interpersonal problems (i.e. 13% to 80%) and use N2 O in risky situations, such as driving under the influence. Evidence for the other criteria is either insufficient or inconclusive. CONCLUSIONS The literature base for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in nitrous oxide (N2 O) users is limited and largely consists of qualitative studies and case studies, but it provides consistent evidence for the presence of at least four SUD criteria in heavy N2 O users. N2 O could well be addictive and should be treated as a potentially addictive substance until systematic assessments can provide evidence-based guidance to users, healthcare professionals and legislators.
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Affiliation(s)
- Sammie Back
- Neuroscience of Addiction (NofA) Lab, Center for Substance use and Addiction Research (CESAR), Department of Psychology, Education and Child Studies, Erasmus University Rotterdam, Rotterdam, The Netherlands
| | - Emese Kroon
- Neuroscience of Addiction (NofA) Lab, Center for Substance use and Addiction Research (CESAR), Department of Psychology, Education and Child Studies, Erasmus University Rotterdam, Rotterdam, The Netherlands
- Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands
| | - Karis Colyer-Patel
- Neuroscience of Addiction (NofA) Lab, Center for Substance use and Addiction Research (CESAR), Department of Psychology, Education and Child Studies, Erasmus University Rotterdam, Rotterdam, The Netherlands
| | - Janna Cousijn
- Neuroscience of Addiction (NofA) Lab, Center for Substance use and Addiction Research (CESAR), Department of Psychology, Education and Child Studies, Erasmus University Rotterdam, Rotterdam, The Netherlands
- Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands
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Mechanisms Involved in the Neurotoxicity and Abuse Liability of Nitrous Oxide: A Narrative Review. Int J Mol Sci 2022; 23:ijms232314747. [PMID: 36499072 PMCID: PMC9738214 DOI: 10.3390/ijms232314747] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 11/29/2022] Open
Abstract
The recreational use of nitrous oxide (N2O) has increased over the years. At the same time, more N2O intoxications are presented to hospitals. The incidental use of N2O is relatively harmless, but heavy, frequent and chronic use comes with considerable health risks. Most importantly, N2O can inactivate the co-factor cobalamin, which, in turn, leads to paresthesia's, partial paralysis and generalized demyelinating polyneuropathy. In some patients, these disorders are irreversible. Several metabolic cascades have been identified by which N2O can cause harmful effects. Because these effects mostly occur after prolonged use, it raises the question of whether N2O has addictive properties, explaining its prolonged and frequent use at high dose. Several lines of evidence for N2O's dependence liability can be found in the literature, but the underlying mechanism of action remains controversial. N2O interacts with the opioid system, but N2O also acts as an N-methyl-D-aspartate (NMDA) receptor antagonist, by which it can cause dopamine disinhibition. In this narrative review, we provide a detailed description of animal and human evidence for N2O-induced abuse/dependence and for N2O-induced neurotoxicity.
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[Acute and chronic toxicities associated with the use and misuse of nitrous oxide: An update]. Rev Med Interne 2021; 43:170-177. [PMID: 34903366 DOI: 10.1016/j.revmed.2021.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 09/07/2021] [Accepted: 10/09/2021] [Indexed: 11/22/2022]
Abstract
Nitrous oxide (N2O) is used since the eighteenth century as an anesthetic and analgesic but also for recreational use. If the labelled uses of N2O and their modalities are nowadays perfectly framed, the misuse of N2O takes very alarming proportions among teenagers and young adults. This misuse is the cause of acute (hypoxia, barotrauma, burns, neuropsychiatric disorders) and chronic complications if repeated (myeloneuropathy, anemia, thrombosis, inhalant use disorder). The main mechanism of the latter is mainly related to a functional deficit in vitamin B12 induced by N2O. The management of acute complications is symptomatic. The management of chronic complications is based on vitamin B12 supplementation. The best biomarker of chronic N2O exposure is the elevation of the plasmatic level of methylmalonic acid. In all cases of recreational misuses, addiction treatment is necessary to prevent complications or their worsening by providing information in order to stop consumption.
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Ramsay DS, Kaiyala KJ, Woods SC. Individual differences in biological regulation: Predicting vulnerability to drug addiction, obesity, and other dysregulatory disorders. Exp Clin Psychopharmacol 2020; 28:388-403. [PMID: 32338936 PMCID: PMC8389185 DOI: 10.1037/pha0000371] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Physiological regulation is so fundamental to survival that natural selection has greatly favored the evolution of robust regulatory systems that use both reactive and preemptive responses to mitigate the disruptive impact of biological and environmental challenges on physiological function. In good health, robust regulatory systems provide little insight into the typically hidden complex array of sensor-effector interactions that accomplish successful regulation. Numerous health disorders have been traced to defective regulatory mechanisms, and generations of scientists have worked to discover ways to correct these defects and restore normal physiological function. Despite progress, numerous chronic health disorders remain resistant to treatment, and indeed for some disorders the incidence is increasing. We propose that an individual's susceptibility to acquire certain persistent dysregulatory disorders can be traced to interindividual variation in how that individual's regulatory system responds to challenges. Preexisting reliable individual differences among regulatory systems are typically unrecognized until appropriate regulatory challenges (e.g., exposure to a drug of abuse) lead to dysregulation (e.g., drug addiction). Specific characteristics of an individual's regulatory responsiveness may include etiological factors that participate in the acquisition, escalation and maintenance of health disorders characterized by dysregulation. By appropriately challenging a healthy individual's regulatory systems to identify its underlying characteristics, it is possible to ascertain whether an individual has an elevated risk for acquiring a dysregulated health condition and thereby enable strategies designed to prevent, rather than treat, the condition. This model is applied to drug addiction, and in addition we relate this approach to other dysregulated conditions such as obesity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).
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Affiliation(s)
- Douglas S. Ramsay
- Department of Oral Health Sciences, University of Washington
- Department of Orthodontics, University of Washington
- Department of Pediatric Dentistry, University of Washington
| | - Karl J. Kaiyala
- Department of Oral Health Sciences, University of Washington
| | - Stephen C. Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati Medical Center
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The effect of nitrous oxide anesthesia on early postoperative opioid consumption and pain. Reg Anesth Pain Med 2014; 39:31-6. [PMID: 24310050 DOI: 10.1097/aap.0000000000000039] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND AND OBJECTIVES Many patients experience moderate to severe postoperative pain. Nitrous oxide (N₂O) exerts analgesia by inhibition of N-methyl-D-aspartate receptors. Ketamine, another N-methyl-D-aspartate receptor antagonist, reduces postoperative opioid consumption and pain. A similar effect of N₂O is plausible, yet understudied. The goal of this study was to determine the effects of N₂O anesthesia on early postsurgical opioid consumption and pain. METHODS This was a retrospective, secondary analysis of the Vitamins In Nitrous Oxide trial, where 500 patients undergoing general anesthesia for noncardiac surgery received 60% N₂O and 125 received no N₂O (otherwise, inclusion/exclusion criteria were identical). Exclusion criteria for this study were regional anesthesia, not extubated after surgery, transfer to intensive care unit, no available postanesthesia care unit record, postsurgical sedation, or treated with naloxone. Primary outcomes were cumulative opioid consumption measured in morphine equivalents and pain scores during the immediate recovery phase. RESULTS Four hundred forty-two patients met inclusion criteria. No difference in intraoperative and postoperative opioid consumption was observed between patients who received N₂O (n = 353) and patients who did not (n = 89). The median [interquartile range] postoperative morphine equivalent dose was 6.7 mg [1.7-14.1 mg] for patients who received N₂O and 6.7 mg [2.1-15.4 mg] for patients who did not (P = 0.73). The maximum pain score was 6 [4-8] for patients who received N₂O versus 6 [3-8] for patients who received N₂O-free anesthesia (P = 0.52). The prevalence of moderate to severe pain was 69% for patients who received N₂O and 68% for patients who did not (P = 0.90). CONCLUSIONS Nitrous oxide anesthesia was not associated with decreased opioid administration, pain, or incidence of moderate to severe pain in the early postoperative phase.
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Abstract
INTRODUCTION Tolerance is observed for a variety of central nervous system depressants including ethanol, which is an anesthetic, but has not been convincingly demonstrated for a potent halogenated volatile anesthetic. Failure to demonstrate tolerance to these agents may be the result of inadequate exposure to anesthetic. In this study, we exposed Xenopus laevis tadpoles to surgical anesthetic concentrations of isoflurane for 1 wk. METHODS Xenopus laevis tadpoles were produced by in vitro fertilization, and exposed to isoflurane (0.59%, 0.98%, 1.52%) or oxygen for 1 wk starting from the time of fertilization. RESULTS Changes in anesthetic EC(50) were small and not in a consistent direction. Control animals had an anesthetic EC(50) of 0.594% +/- 0.003% isoflurane. Tadpoles exposed to 1.52% isoflurane had a lower EC(50) than controls (by 16%), whereas tadpoles raised under 0.59% and 0.98% isoflurane had higher EC(50)s than control (by 4.7% and 7.4%, respectively). CONCLUSION We provide the first description of week-long exposures of vertebrates to surgical anesthetic concentrations of isoflurane, and the first report of such exposures in developing vertebrates. Tolerance to isoflurane does not occur in developing Xenopus laevis tadpoles. Taken together with studies in other organisms, the development of tolerance to ethanol but not isoflurane suggests that mechanisms shared by these drugs probably do not account for the development of tolerance.
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Collado V, Nicolas E, Faulks D, Hennequin M. A review of the safety of 50% nitrous oxide/oxygen in conscious sedation. Expert Opin Drug Saf 2007; 6:559-71. [PMID: 17877443 DOI: 10.1517/14740338.6.5.559] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Few studies into conscious sedation with 50% nitrous oxide/oxygen premix (50% N2O/O2) have been conducted in accordance with Good Clinical Practice in Clinical Trials. Of the 140 articles retained in this review, the incidence of adverse events (AEs) varied in the range of 0-68% according to the indications. When other drugs and/or local anaesthesia were used concomitantly, the relative risk for nausea and vomiting increased whereas it decreased for vertigo or hallucinations. Only one study examined potential causal relationship between serious AEs and the 50% N2O/O2 gas itself, giving a risk for a serious AE directly due to the gas of 3/10,000 administrations. No analysis of the effect of the method of administration was possible, nor could conclusions be drawn relating to the risk of occupational exposure.
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Affiliation(s)
- Valérie Collado
- Univ Clermont1, EA 3847, Faculté d'Odontologie, 11 bvd Charles de Gaulle, F-63000 Clermont-Ferrand, France.
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Matsushita Y, Ishikawa M, Abe K, Utsunomiya I, Chikuma T, Hojo H, Hoshi K, Quock RM, Taguchi K. Involvement of the protein kinase Cγ isoform in development of tolerance to nitrous oxide–induced antinociception in mice. Neuroscience 2007; 148:541-7. [PMID: 17681696 DOI: 10.1016/j.neuroscience.2007.06.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Revised: 06/11/2007] [Accepted: 06/18/2007] [Indexed: 11/23/2022]
Abstract
Prolonged exposure to nitrous oxide (N2O) results in development of acute tolerance to its antinociceptive effect. Cross-tolerance to N2O-induced antinociception is also observed in morphine-tolerant animals. Despite increasing evidence of tolerance development to N2O-induced antinociception, the details of the mechanisms that underlie this tolerance remain unknown. The present study was conducted to investigate the involvement of brain protein kinase C (PKC) isoform in these two types of tolerance to N2O-induced antinociception in mice. Prolonged exposure (41 min in total, including 30 min pre-exposure and 11 min of antinociceptive testing) to 70% N2O produced a reduction in N2O-induced antinociception, indicating development of acute tolerance. The prolonged exposure to 70% N2O caused an activation of PKCgamma isoform in the brain, but not the PKCepsilon isoform. Pretreatment with a PKCgamma-antisense oligonucleotide but not the corresponding mismatch oligonucleotide (i.c.v.) prevented the development of acute tolerance to N2O-induced antinociception. Chronic morphine treatment (10 mg/kg, s.c., b.i.d. for 5 days) resulted in development of tolerance to morphine-induced antinociception and cross-tolerance to N2O-induced antinociception. The development of tolerance to morphine and cross-tolerance to N2O were both inhibited by pretreatment with PKC inhibitor, chelerythrine (1 nmol, i.c.v.). Morphine-tolerant mice showed an activation of PKC within the brain, which was suppressed by pretreatment with chelerythrine (1 nmol, i.c.v.). Thus, activation of brain PKC, in particular, the PKCgamma isoform, appears to play an important role in the development of both acute tolerance and cross-tolerance to N2O-induced antinociception in mice.
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Affiliation(s)
- Y Matsushita
- Department of Pharmacotherapeutics, Showa Pharmaceutical University, PO Box 3-3165, Higashitamagawagakuen, Tokyo 194-8543, Japan
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Vahle-Hinz C, Detsch O, Hackner C, Kochs E. Corresponding minimum alveolar concentrations of isoflurane and isoflurane/nitrous oxide have divergent effects on thalamic nociceptive signalling. Br J Anaesth 2007; 98:228-35. [PMID: 17210736 DOI: 10.1093/bja/ael332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Suppression of nociceptive signalling in the thalamus is considered to contribute significantly to the anaesthetic state. Assuming additivity of anaesthetic mixtures, our study assessed the effects of corresponding minimum alveolar concentrations (MACs) of isoflurane and isoflurane/nitrous oxide on thalamic nociceptive signalling. METHODS Nociceptive response activity (elicited by controlled radiant heat stimuli applied to cutaneous receptive fields) of single thalamic neurons was compared in rats anaesthetized at approximately 1.1 and approximately 1.4 MAC isoflurane with that at approximately 1.1 and approximately 1.4 MAC isoflurane/nitrous oxide. RESULTS Under baseline anaesthesia ( approximately 0.9 MAC isoflurane), noxious stimulation elicited excitatory responses in all neurons (n = 19). These responses were uniformly suppressed at approximately 1.1 and approximately 1.4 MAC isoflurane. In contrast, at approximately 1.1 and approximately 1.4 MAC isoflurane/nitrous oxide, excitatory responses no different to baseline were still present in 64 and 37% of the neurons, respectively. CONCLUSIONS These data demonstrate a pronounced nitrous oxide-induced response variability. It appears that, with respect to thalamic transfer of nociceptive information, the interaction of isoflurane and nitrous oxide may not be compatible with the concept of additivity and that the antinociceptive potency of nitrous oxide is considerably less than previously reported.
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Affiliation(s)
- C Vahle-Hinz
- Institut für Neurophysiologie und Pathophysiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.
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Collado V, Hennequin M, Faulks D, Mazille MN, Nicolas E, Koscielny S, Onody P. Modification of behavior with 50% nitrous oxide/oxygen conscious sedation over repeated visits for dental treatment a 3-year prospective study. J Clin Psychopharmacol 2006; 26:474-81. [PMID: 16974188 DOI: 10.1097/01.jcp.0000236660.01039.eb] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In various medical domains, inhalation of nitrous oxide (N2O) in oxygen (O2) is indicated to alleviate pain and anxiety during routine treatment. Repeat treatment may often be indicated. Little data are available, however, to evaluate the long-term efficacy and side effects of reiterated N2O/O2 sedation. The aim of this study was to compare behavior during dental treatment under a premix of 50% N2O/O2 between first experience and repeat experiences of sedation in a cohort of uncooperative patients. Five hundred forty-three patients (age range, 1-94 years; mean, 17 +/- 16 years) experiencing conscious sedation for dental treatment for the first time were recruited at a special care unit during 3 years. A modified Venham scale was used to evaluate patient behavior at 5 steps during each session. Completion of planned treatment and occurrence of adverse side effects of sedation were additional criteria. Patients experienced sedation for the first time for 378 sessions, and the session was a repeat experience in 843 cases (number of visits: range, 1-6). Patient cooperation significantly improved during visits at first contact with the dentist and when applying the mask (P < 0.0001, between sessions 1 and 2). Between the first and the third sessions, the percentage of very uncooperative patients decreased from 23% to 3.7% at first contact with the dentist and from 22.3% to 8.5% on application of the mask. Experience of reiterated dental treatment under sedation with 50% N2O/O2 premix helps uncooperative patients to cope with dental treatment in the long term.
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Affiliation(s)
- Valérie Collado
- Univ Clermont1, UFR d'Odontologie, Clermont-Ferrand, France.
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Laurent G, Bertaux G, Martel A, Fraison M, Fromentin S, Gonzalez S, Pierre FS, Wolf JE. A Randomized Clinical Trial of Continuous Flow Nitrous Oxide and Nalbuphine Infusion for Sedation of Patients During Radiofrequency Atrial Flutter Ablation. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2006; 29:351-7. [PMID: 16650261 DOI: 10.1111/j.1540-8159.2006.00352.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND In patients with common atrial flutter (CAF), radiofrequency ablation (RFA) causes discomfort. Patients undergoing RFA often feel pain which is difficult to control as the mechanisms are unclear. HYPOTHESIS Inhaled nitrous oxide (N2O) is a potent sedative-analgesic-anxiolytic agent that may relieve anxiety and discomfort during CAF ablation. METHODS AND RESULTS In a prospective randomized study, the effect of Inhaled N2O was compared with that of intravenous sedation with Nalbuphine during CAF ablation in 76 patients (64 +/- 13 years, 56 men). We used a 24 pole mapping catheter around the tricuspid annulus and a 8-mm tip ablation catheter for each patient. Forty-two patients (group 1) underwent radiofrequency (RF) application to the cavotricuspid isthmus 5 minutes after the beginning of inhalation of a (50% N2O/50% O2) mixture. Thirty-four patients (group 2), underwent the first RF application 15 minutes after the end of an infusion of Nalbuphine (20 mg delivered over 15 minutes). Ablation-related anxiety and discomfort were assessed using a visual analog scale (VAS) ranging from 0 to 100 mm, with 0 correlating to the statement "no pain at all" and 100 with "the worst possible pain." The VAS score was determined at the end of each application. The number of RF applications (group 1; 10 +/- 8 vs group 2; 11 +/- 6, P = NS) and procedure duration (group 1; 75 +/- 53 minutes vs group 2; 72 +/- 45 minutes, P = NS), were similar for the two groups. N(2)O sedation compared with nalbuphine infusion reduced VAS for anxiety (10 mm +/- 8 vs 58 mm +/- 22, P < 0.05) and for discomfort (18 mm +/- 9 vs 45 mm +/- 34, P < 0.01), respectively. Although there was more frequent vomiting in group 1; 7 of 42 (17%) than in group 2; 3 of 34 (9%), P < 0.05, patients were less likely to have hypotension during the procedure 1 of 42 (2.5%) versus 4 of 34 (12%), P < 0.05, respectively. CONCLUSION Inhalation of a (50% N2O/50% O2) mixture during RF ablation for atrial flutter is a safe and efficient way to reduce anxiety and discomfort caused by RF applications.
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Affiliation(s)
- Gabriel Laurent
- Department of Cardiology, University Hospital Dijon, France.
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Ishikawa M, Matsushita Y, Abe K, Utsunomiya I, Hoshi K, Quock RM, Taguchi K. Involvement of brain protein kinase C in nitrous oxide-induced antinociception in mice. Neuroscience 2006; 140:227-33. [PMID: 16533570 DOI: 10.1016/j.neuroscience.2006.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2005] [Revised: 12/23/2005] [Accepted: 02/01/2006] [Indexed: 11/22/2022]
Abstract
Exposure of mice to the anesthetic gas nitrous oxide (N(2)O) produces a marked antinociceptive effect. Protein kinase C is a key regulatory enzyme that may be targeted by general anesthetics. However, a relationship between N(2)O-induced antinociception and protein kinase C has yet to be established. The present study was conducted to identify whether protein kinase C might influence N(2)O-induced antinociception in mice. Regular exposure (11 min) to N(2)O produced concentration-dependent antinociception in mice, as determined using the abdominal constriction test. N(2)O-induced antinociception was attenuated by i.c.v. pretreatment with phorbol 12,13-dibutyrate, a protein kinase C activator. This phorbol 12,13-dibutyrate antagonism of N(2)O-induced antinociception was reversed by i.c.v. pretreatment with calphostin C, a protein kinase C inhibitor. Long-term exposure (41 min in total, including 30 min prior to, and 11 min of analgesic testing) to 70% N(2)O produced reduced analgesic effects, compared with regular exposure to 70% N(2)O, thus indicating acute tolerance to N(2)O-induced antinociception. However, mice pretreated with calphostin C, chelerythrine, which is another protein kinase C inhibitor, and phorbol 12,13-dibutyrate, did not develop acute tolerance. Regarding activation of protein kinase C, regular exposure to 70% N(2)O did not increase protein kinase C within the membrane fraction of brain tissue, as determined by immunoblot analysis, but long-term exposure to 70% N(2)O did. The i.c.v. pretreatment with calphostin C and phorbol 12,13-dibutyrate prevented the increase in protein kinase C observed with long-term exposure to 70% N(2)O. These results suggest that brain protein kinase C negatively regulates the antinociceptive effect of N(2)O, and that activation of brain protein kinase C is related to the development of acute tolerance to N(2)O-induced antinociception in mice.
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Affiliation(s)
- M Ishikawa
- Department of Pharmacotherapeutics, Showa Pharmaceutical University, P.O. Box 3-3165, Higashitamagawagakuen, Tokyo 194-8543, Japan
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Abstract
Most general anaesthetic agents produce anaesthesia by increasing the activity of inhibitory gamma-aminobutyric acid type A receptors. The effects of ketamine, xenon and nitrous oxide on these receptors are, however, negligible. These anaesthetic agents potently inhibit excitatory N-methyl-D-aspartate receptors. Although these anaesthetic agents display some similar clinical features, such as potent analgesic effects, there are some important differences. Ketamine and nitrous oxide produce sympathomimetic effects, whereas xenon produces a sympatholytic effect. In addition, these anaesthetic agents return differential signals on clinical available anaesthetic depth monitors such as the bispectral index and mid-latency auditory evoked potential. Ketamine and nitrous oxide do not per se decrease the bispectral index. However, xenon decreases the bispectral index in a concentration-dependent manner. Similarly, ketamine and nitrous oxide do not suppress the mid-latency auditory evoked potential whereas xenon does. Thus, anaesthetic depth monitors fail to describe consciousness accurately when ketamine and nitrous oxide are used.
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Affiliation(s)
- Kazuyoshi Hirota
- Department of Anesthesiology, University of Hirosaki School of Medicine, Hirosaki 036-8563, Japan.
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