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Gernez E, Lee GR, Niguet JP, Zerimech F, Bennis A, Grzych G. Nitrous Oxide Abuse: Clinical Outcomes, Pharmacology, Pharmacokinetics, Toxicity and Impact on Metabolism. TOXICS 2023; 11:962. [PMID: 38133363 PMCID: PMC10747624 DOI: 10.3390/toxics11120962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 11/22/2023] [Accepted: 11/26/2023] [Indexed: 12/23/2023]
Abstract
The recreational use of nitrous oxide (N2O), also called laughing gas, has increased significantly in recent years. In 2022, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) recognized it as one of the most prevalent psychoactive substances used in Europe. Chronic nitrous oxide (N2O) exposure can lead to various clinical manifestations. The most frequent symptoms are neurological (sensitive or motor disorders), but there are also other manifestations like psychiatric manifestations or cardiovascular disorders (thrombosis events). N2O also affects various neurotransmitter systems, leading to its anesthetic, analgesic, anxiolytic and antidepressant properties. N2O is very challenging to measure in biological matrices. Thus, in cases of N2O intoxication, indirect biomarkers such as vitamin B12, plasma homocysteine and plasma MMA should be explored for diagnosis and assessment. Others markers, like oxidative stress markers, could be promising but need to be further investigated.
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Affiliation(s)
- Emeline Gernez
- CHU de Lille, Centre de Biologie Pathologie Génétique, 59000 Lille, France; (E.G.); (F.Z.)
| | | | - Jean-Paul Niguet
- Service de Neurologie, Hôpital Saint Vincent de Paul–GHICL, 59000 Lille, France;
| | - Farid Zerimech
- CHU de Lille, Centre de Biologie Pathologie Génétique, 59000 Lille, France; (E.G.); (F.Z.)
| | - Anas Bennis
- Assistance Publique—Hôpitaux de Paris, Service de Neurologie, Groupe Hospitalier Universitaire Paris Sud, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France;
| | - Guillaume Grzych
- CHU de Lille, Centre de Biologie Pathologie Génétique, 59000 Lille, France; (E.G.); (F.Z.)
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SCH 23390 inhibits the acquisition of nitrous oxide-induced conditioned place preference and the changes in ERK phosphorylation expression in nucleus accumbens of mice. Neurosci Lett 2022; 781:136674. [PMID: 35525502 DOI: 10.1016/j.neulet.2022.136674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 04/27/2022] [Accepted: 04/29/2022] [Indexed: 12/15/2022]
Abstract
Nitrous oxide (N2O) has a long history of abuse, but its abuse mechanism has not been clear yet. This research aimed at the possibility of mesolimbic dopaminergic system (MLDS) involved in the rewarding effect of N2O. In this work, the rewarding behavior of N2O in mice was evaluated using a typical gas-administered conditioned place preference (CPP) procedure. SCH 23390, a Dopamine D1 receptor (D1R) antagonist, and Haloperidol, a Dopamine D2 receptor (D2R) antagonist were administered during CPP to evaluate the role of dopamine receptors in the N2O-induced CPP. The accompanying changes in phosphorylation of extracellular signal-regulated kinase (ERK) in MLDS related brain regions, including the ventral tegmental area (VTA), caudate putamen (CPu), prefrontal cortex (PFC), and nucleus accumbens (NAc) were measured to assess the neural plasticity changes in the CPP mice by Western blot analysis. Results revealed that 60% N2O induced CPP in the gas-administered mice and promoted the ERK phosphorylation (p-ERK) in the NAc and CPu during the test session of the CPP test. Pretreatment of SCH 23390 (0.5mg/kg) inhibited the acquisition of N2O-induced CPP and the enhanced p-ERK in NAc.It suggested that Dopamine D1 receptor may play an important role in the acquisition of N2O-induced CPP and the accompanied ERK activation in the NAc, which provide insight into the molecular mechanism in the rewarding properties of nitrous oxide.
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Al-Noori S, Cimpan A, Maltzer Z, Kaiyala KJ, Ramsay DS. Plasma corticosterone, epinephrine, and norepinephrine levels increase during administration of nitrous oxide in rats. Stress 2018; 21:274-278. [PMID: 29145764 PMCID: PMC6310116 DOI: 10.1080/10253890.2017.1402175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Nitrous oxide (N2O) is a gaseous drug with abuse potential. Despite its common clinical use, little is known about whether N2O administration activates the HPA axis and/or the sympathetic adrenomedullary system. The goal of this study was to determine whether 60% N2O alters plasma concentrations of corticosterone (CORT), epinephrine (EPI), and norepinephrine (NE) in male Long-Evans rats. A gas-tight swivel assembly in the lid of a gas administration chamber allowed the remote collection of blood samples from an indwelling jugular vein catheter at four time-points: baseline and at 30, 60, and 120 min during a two-hour administration of 60% N2O. Relative to baseline, plasma CORT (n = 9) was significantly elevated at all three time-points during N2O inhalation (mixed model analysis, p = .001) and plasma EPI and NE levels were each significantly elevated (n = 8, p ≤ .001) at the 30 min assessment. EPI then declined and did not differ from baseline at the 60 and 120 min assessments (p > .05) whereas NE remained elevated (120 min, p = .001). Administration of 60% N2O increases circulating CORT, EPI, and NE, supporting N2O as a physiological stressor. An N2O-induced increase in CORT is consistent with the observation that addictive drugs typically activate the HPA axis causing increased plasma levels of glucocorticoids. Allostatic models of drug addiction typically involve stress systems and the possible role of stress hormones in N2O-induced allostatic dysregulation is discussed.
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Affiliation(s)
- Salwa Al-Noori
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
- Division of Biological Sciences, School of STEM, University of Washington, Bothell, WA, USA
| | - Andreas Cimpan
- Division of Biological Sciences, School of STEM, University of Washington, Bothell, WA, USA
| | - Zoe Maltzer
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
| | - Karl J. Kaiyala
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
| | - Douglas S. Ramsay
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
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van Amsterdam J, Nabben T, van den Brink W. Recreational nitrous oxide use: Prevalence and risks. Regul Toxicol Pharmacol 2015; 73:790-6. [PMID: 26496821 DOI: 10.1016/j.yrtph.2015.10.017] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 10/14/2015] [Accepted: 10/19/2015] [Indexed: 02/02/2023]
Abstract
Nitrous oxide (N2O; laughing gas) is clinically used as a safe anesthetic (dentistry, ambulance, childbirth) and appreciated for its anti-anxiety effect. Since five years, recreational use of N2O is rapidly increasing especially in the dance and festival scene. In the UK, N2O is the second most popular recreational drug after cannabis. In most countries, nitrous oxide is a legal drug that is widely available and cheap. Last month prevalence of use among clubbers and ravers ranges between 40 and almost 80 percent. Following one inhalation, mostly from a balloon, a euphoric, pleasant, joyful, empathogenic and sometimes hallucinogenic effect is rapidly induced (within 10 s) and disappears within some minutes. Recreational N2O use is generally moderate with most users taking less than 10 balloons of N2O per episode and about 80% of the users having less than 10 episodes per year. Side effects of N2O include transient dizziness, dissociation, disorientation, loss of balance, impaired memory and cognition, and weakness in the legs. When intoxicated accidents like tripping and falling may occur. Some fatal accidents have been reported due to due to asphyxia (hypoxia). Heavy or sustained use of N2O inactivates vitamin B12, resulting in a functional vitamin B12 deficiency and initially causing numbness in fingers, which may further progress to peripheral neuropathy and megaloblastic anemia. N2O use does not seem to result in dependence. Considering the generally modest use of N2O and its relative safety, it is not necessary to take legal measures. However, (potential) users should be informed about the risk of vitamin B12-deficiency related neurological and hematological effects associated with heavy use.
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Affiliation(s)
- Jan van Amsterdam
- Department of Psychiatry, Academic Medical Center, University of Amsterdam, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands.
| | - Ton Nabben
- Bonger Institute for Criminology, University of Amsterdam, P.O. Box 1030, 1000 BA Amsterdam, The Netherlands
| | - Wim van den Brink
- Department of Psychiatry, Academic Medical Center, University of Amsterdam, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands; Amsterdam Institute for Addiction Research, Academic Medical Center, P.O. Box 75867, 1070 AW Amsterdam, The Netherlands
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Assessment of Pharmacokinetic and Pharmacodynamic Interactions Between Albumin-Fused Mutated Butyrylcholinesterase and Intravenously Administered Cocaine in Recreational Cocaine Users. J Clin Psychopharmacol 2015; 35:396-405. [PMID: 26082975 DOI: 10.1097/jcp.0000000000000347] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
UNLABELLED Cocaine dependence presents a major public health issue, and to date, no pharmacotherapies are approved for its treatment. TV-1380 is a novel recombinant albumin-fused mutated butyrylcholinesterase (Albu-BChE) that has increased catalytic efficiency for cocaine compared with wild-type BChE and therefore has the potential to facilitate abstinence in cocaine-dependent subjects by decreasing exposure to cocaine and its reinforcing effects. METHODS This randomized, double-blind, placebo-controlled, parallel-group study in nondependent cocaine users was conducted to evaluate the effect of a single intramuscular dose of Albu-BChE (50, 100, and 300 mg) on the pharmacokinetic and metabolic profile of intravenous cocaine infusions (40 mg) administered at baseline and at 24, 96, and 168 hours after Albu-BChE dosing, to assess safety of coadministering Albu-BChE and cocaine, and to explore the subjective responses to cocaine infusions after Albu-BChE dosing. RESULTS Administration of Albu-BChE resulted in significant dose-dependent reductions in cocaine exposure (maximum concentration, area under the curve) and half-life. Effects were greatest at 24 hours after Albu-BChE dose, but were sustained up to 168 hours. Spearman correlations indicated a significant negative relationship between Albu-BChE concentration and cocaine clearance and exposure. Consistent with its mechanism of action, Albu-BChE also shifted cocaine metabolism toward preferential formation of ecgonine methyl ester. Administration of Albu-BChE was associated with modest decreases in subjective reports of feeling high and willingness to take cocaine again after cocaine infusion. Coadministration of Albu-BChE and cocaine was safe and well tolerated. CONCLUSIONS Administration of Albu-BChE at single doses of 50, 100, and 300 mg safely resulted in long-lasting decreases in cocaine exposure in recreational cocaine users.
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Tracy ME, Slavova-Hernandez GG, Shelton KL. Assessment of reinforcement enhancing effects of toluene vapor and nitrous oxide in intracranial self-stimulation. Psychopharmacology (Berl) 2014; 231:1339-50. [PMID: 24186077 PMCID: PMC3954938 DOI: 10.1007/s00213-013-3327-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 10/08/2013] [Indexed: 11/29/2022]
Abstract
RATIONALE Despite widespread abuse, there are few validated methods to study the rewarding effects of inhalants. One model that may have utility for this purpose is intracranial self-stimulation (ICSS). OBJECTIVES This study aims to compare and contrast the ICSS reward-facilitating effects of abused inhalants to other classes of abused drugs. Compounds were examined using two different ICSS procedures in mice to determine the generality of each drug's effects on ICSS and the sensitivity of the procedures. METHODS Male C57BL/6J mice with electrodes implanted in the medial forebrain bundle were trained under a three-component rate-frequency as well as a progressive ratio (PR) ICSS procedure. The effects of nitrous oxide, toluene vapor, cocaine, and diazepam on ICSS were then examined. RESULTS Concentrations of 1,360-2,900 parts per million (ppm) inhaled toluene vapor significantly facilitated ICSS in the rate-frequency procedure and 1,360 ppm increased PR breakpoint. A concentration of 40 % nitrous oxide facilitated ICSS in the rate-frequency procedure but reduced PR breakpoint. Doses of 3-18 mg/kg cocaine facilitated ICSS in the rate-frequency procedure, and 10 and 18 mg/kg increased PR breakpoint. Doses of 1 and 3 mg/kg diazepam facilitated ICSS in the rate-frequency procedure, and 3 mg/kg increased PR breakpoint. CONCLUSIONS The reinforcement-facilitating effect of toluene in ICSS is at least as great as diazepam. By contrast, nitrous oxide weakly enhances ICSS in only the rate-frequency procedure. The data suggest that the rate-frequency procedure may be more sensitive than the PR schedule to the reward-facilitating effects of abused inhalants.
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Affiliation(s)
- Matthew E. Tracy
- Virginia Commonwealth University School of Medicine Department of Pharmacology and Toxicology 410 North 12th Street, Room 746D Richmond, Virginia 23298-0613
| | - Galina G. Slavova-Hernandez
- Virginia Commonwealth University School of Medicine Department of Pharmacology and Toxicology 410 North 12th Street, Room 746D Richmond, Virginia 23298-0613
| | - Keith L. Shelton
- Virginia Commonwealth University School of Medicine Department of Pharmacology and Toxicology 410 North 12th Street, Room 746D Richmond, Virginia 23298-0613,Corresponding Author Keith L Shelton, Ph.D. Phone: 804-827-2104 Fax: 804-828-2117
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Zacny JP, Walker DJ, Derus LM. Choice of nitrous oxide and its subjective effects in light and moderate drinkers. Drug Alcohol Depend 2008; 98:163-8. [PMID: 18640794 PMCID: PMC2566819 DOI: 10.1016/j.drugalcdep.2008.06.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2008] [Revised: 05/29/2008] [Accepted: 06/02/2008] [Indexed: 11/27/2022]
Abstract
BACKGROUND Alcohol-drinking status has been shown to modulate the reinforcing and subjective effects of a number of drugs. We have previously published two studies on the modulating effects of alcohol-drinking status on choice for, and subjective effects of, nitrous oxide, but the results were equivocal. Using a methodology different from our previous studies, we sought to determine in a more definitive fashion the degree to which the choice of nitrous oxide and its subjective effects were modulated by drinking status. METHODS Four concentrations of nitrous oxide (0, 20, 30, and 40%) were administered to 16 moderate drinkers (MDs) and 16 light drinkers (LDs) across four 3.5-h sessions. During experimental sessions, subjects first completed two 10-min sampling trials in which one of the nitrous oxide concentrations and placebo (100% oxygen) were inhaled. Subjective and psychomotor tests were given 5min into each sampling trial. During the subsequent choice period, subjects were allowed to choose what they wanted to inhale (drug, placebo, or "drug-free air") on nine contiguous 5-min choice trials. RESULTS Choice of nitrous oxide was modulated by drinking status: MDs but not LDs chose nitrous oxide significantly more times than placebo, and MDs also chose nitrous oxide significantly more times than did LDs. At each active nitrous oxide concentration, MDs reported more abuse liability-related subjective effects, especially at the 20% and 30% concentrations. CONCLUSIONS The results of the present study provide more conclusive evidence that choice as well as subjective effects of nitrous oxide is modulated by alcohol-drinking status.
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Affiliation(s)
- James P. Zacny
- Department of Anesthesia and Critical Care, The University of Chicago, Chicago, IL 60637, USA
| | - Diana J. Walker
- The Chicago School of Professional Psychology, Chicago, IL 60610, USA
| | - Lindsay M. Derus
- Department of Anesthesia and Critical Care, The University of Chicago, Chicago, IL 60637, USA
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Wilson JE, Kiselanova N, Stevens Q, Lutz R, Mandler T, Tran ZV, Wischmeyer PE. A survey of inhalational anaesthetic abuse in anaesthesia training programmes. Anaesthesia 2008; 63:616-20. [PMID: 18477273 DOI: 10.1111/j.1365-2044.2008.05444.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
This study aims to assess the prevalence and outcomes of inhalational anaesthetic abuse among anaesthesia training programmes. Online surveys were completed by chairpersons of academic anaesthesia training programmes in the United States. The response rate was 84% (106/126 programmes). Twenty-two percent of the departments had had at least one incident of inhalational anaesthetic abuse. Forty-eight percent (15/31) of the persons abusing inhalational anaesthetics were sent for rehabilitation. Only 22% (7/31) of those found to be abusing inhalational anaesthetics were ultimately able to return successfully to anaesthesia practice with sustained recovery. The mortality rate among individuals found abusing inhalational anaesthetics was 26% (8/31). The majority of the anaesthesia departments (97/104, 93%) did not have any pharmacy accounting of inhalational anaesthetics. This is the first published survey of inhalational anaesthesia abuse. Inhalational anaesthetic abuse should be considered in at-risk individuals or those with a history of substance abuse. The concern about substance abuse is not unique to American anaesthetists. Countries around the world deal with similar substance abuse issues.
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Affiliation(s)
- J E Wilson
- Department of Anaesthesia, University of Colorado Health Sciences Center, Denver, Colorado, USA
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Zacny JP, Walker DJ, Drum M, Sells M. Choice of sevoflurane and its subjective and psychomotor effects in light and moderate drinkers. Drug Alcohol Depend 2008; 94:101-8. [PMID: 18077105 PMCID: PMC2288701 DOI: 10.1016/j.drugalcdep.2007.10.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 10/18/2007] [Accepted: 10/18/2007] [Indexed: 11/30/2022]
Abstract
BACKGROUND Sevoflurane, an inhalant of the volatile anesthetic class, has neurobiological and behavioral effects in common with abused inhalants and ethanol. We sought to determine if choice for subanesthetic doses of sevoflurane, and its subjective and psychomotor effects, would differ as a function of alcohol-drinking status in healthy volunteers. METHODS The effects of four concentrations of sevoflurane (0, 0.2, 0.4, 0.8% sevoflurane in oxygen) were studied in 16 light drinkers and 16 moderate drinkers. During each of four sessions, subjects sampled a concentration of sevoflurane and 100% O(2) (placebo) for 10 min each. Subjective and psychomotor testing commenced 5 min into each sampling trial. Later, within the session, subjects chose nine times, once every 5 min, among sevoflurane (e.g., "Agent A"), placebo (e.g., "Agent B," 100% O(2)), or neither (and were administered 100% O(2), identified as "drug-free air"). RESULTS Choice for sevoflurane at the 0.4% concentration was significantly higher in the moderate drinkers than in the light drinkers. A number of subjective effects reported during inhalation of sevoflurane were markedly lower in the moderate-drinking group than in the light-drinking group. However, psychomotor impairment induced by sevoflurane was similar in magnitude in both groups. CONCLUSIONS Alcohol-drinking status affected sevoflurane choice. The results are consistent with several studies comparing light and heavier drinkers, using other drugs. Although both drinking groups were similarly impaired by sevoflurane, the moderate drinkers reported less of a subjective response than light drinkers, suggestive of cross-tolerance.
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Affiliation(s)
- James P. Zacny
- Department of Anesthesia and Critical Care The University of Chicago Chicago. Illinois USA
| | - Diana J. Walker
- Department of Anesthesia and Critical Care The University of Chicago Chicago. Illinois USA
| | - Melinda Drum
- Department of Health Studies The University of Chicago Chicago. Illinois USA
| | - Molly Sells
- Department of Anesthesia and Critical Care The University of Chicago Chicago. Illinois USA
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Beckman NJ, Zacny JP, Walker DJ. Within-subject comparison of the subjective and psychomotor effects of a gaseous anesthetic and two volatile anesthetics in healthy volunteers. Drug Alcohol Depend 2006; 81:89-95. [PMID: 16024183 DOI: 10.1016/j.drugalcdep.2005.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 06/09/2005] [Accepted: 06/13/2005] [Indexed: 11/22/2022]
Abstract
Inhalant abuse is a serious public health problem throughout the world. The present study compared the states of intoxication produced by three inhaled anesthetics that represent two of the three major classes of abused inhalants, as classified by [Balster, R.L., 1998. Neural basis of inhalant abuse. Drug Alcohol Depend 51, 207-214.]. Isoflurane and sevoflurane represent the class of volatile substances, and nitrous oxide (N2O) comprises a class of its own. Fourteen healthy volunteers inhaled the vehicle (100% O2) and two concentrations each of isoflurane (0.1 and 0.2%), sevoflurane (0.2 and 0.4%), and N2O (15 and 30%) for 40 min each, across seven separate sessions. Drug concentrations were chosen to produce similar ratings of drug effect strength and similar impairment on a psychomotor test, the digit-symbol substitution test (DSST). Ratings of drug effect strength and performance on the DSST were similar across drugs; however, the volatile anesthetics produced greater sedation and greater impairment on three other psychomotor tests than N2O, whereas N2O produced a greater magnitude of putatively pleasant and psychedelic-like subjective effects. These results are consistent with the drugs' putative receptor mechanisms of action and confirm Balster's classification of the volatile anesthetics into a class distinct from N2O.
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Affiliation(s)
- Nancy J Beckman
- Department of Anesthesia and Critical Care, The University of Chicago, 5841 S. Maryland Avenue, MC 4028, Chicago, IL 60637, USA
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Walker DJ, Beckman NJ, Zacny JP. Reinforcing and subjective effects of the volatile anesthetic, sevoflurane. Drug Alcohol Depend 2004; 76:191-201. [PMID: 15488343 DOI: 10.1016/j.drugalcdep.2004.05.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2004] [Revised: 05/03/2004] [Accepted: 05/04/2004] [Indexed: 11/28/2022]
Abstract
Sevoflurane is a volatile anesthetic that is chemically similar to volatile substances of abuse and can be safely administered to humans in laboratory research. In this study, the reinforcing and subjective effects of five concentrations of sevoflurane (0, 0.2, 0.4, 0.6, 0.8% sevoflurane in O2) were studied in 20 non-drug-abusers. During each of five sessions, subjects sampled a concentration of sevoflurane and 100% O2 (placebo) for 10 min each. Later, within the session, they chose nine times, once every 5 min, among sevoflurane (e.g. "Agent A"), placebo (e.g. "Agent B"), or neither (and were administered 100% O2, identified as "drug-free air"). Although "neither" was selected most frequently, mean preference ratios (sevoflurane choices/[sevoflurane choices+placebo choices]) and total sevoflurane choice peaked at the 0.4% concentration. Choice patterns varied across subjects, with some subjects never choosing sevoflurane and other subjects showing monotonic increasing or bitonic concentration-choice functions. Concentration-related increases in subjective effects were observed, including effects that are putatively associated with abuse liability. Ratings of drug liking and of wanting to inhale the drug again were positively correlated with sevoflurane choice. This study shows that sevoflurane can function as a reinforcer and produce abuse liability-related subjective effects in some healthy volunteers.
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Affiliation(s)
- Diana J Walker
- Department of Anesthesia and Critical Care, University of Chicago, 5841 S. Maryland Ave., MC 4028, Chicago, IL 60637, USA.
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Abstract
Induction of c-Fos has previously been used to map locations of cells in the central nervous system (CNS) that are activated by ethanol administration. Only a few studies examining a restricted range of CNS areas have identified brain areas activated by nitrous oxide (N(2)O). Because ethanol and N(2)O have overlapping physiological, psychological and behavioral effects, we hypothesized that these drugs act on similar sites in the CNS. To test this hypothesis, we assessed c-Fos-like immunoreactivity in brain slices from male Long-Evans rats that received a 2-h exposure of 0, 20, 40 or 60% N(2)O (n=5 each) immediately prior to sacrifice. N(2)O administration produced significant (P<0.05) dose-related increases of c-Fos expression in several forebrain regions, including the hypothalamic supraoptic and paraventricular nuclei, the thalamic paraventricular nucleus, the amygdala, and in retrosplenial cortex. In the midbrain, N(2)O caused significant dose-related c-Fos expression in the Edinger-Westphal nucleus. Finally, the pontine locus coeruleus, and two medullary regions, the nucleus of the solitary tract and ventrolateral medulla, also showed significant dose-related N(2)O-induced c-Fos expression. Most of the brain areas identified as targets of N(2)O are also activated by ethanol administration. The overlapping pattern of c-Fos induced by ethanol and N(2)O suggests that these drugs may cause comparable central activity by acting on similar neuronal pathways.
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Affiliation(s)
- Karl J Kaiyala
- School of Dentistry, University of Washington, Seattle 98195, USA.
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Walker DJ, Zacny JP. Bitonic dose-response functions for reinforcing and self-reported effects of nitrous oxide in humans. Pharmacol Biochem Behav 2003; 74:851-7. [PMID: 12667899 DOI: 10.1016/s0091-3057(03)00015-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The reinforcing and self-reported effects of nitrous oxide (10%, 30%, and 50% N(2)O in O(2)) were examined in 13 humans. During each of three sessions, subjects sampled one dose of N(2)O and 100% O(2) (placebo) for 10 min each, separated by 30-min recovery periods. The agents were identified by letter code, and later in the session, subjects chose nine times, once every 5 min, among N(2)O (e.g., "Agent A"), placebo (e.g., "Agent B"), or "neither" (also 100% O(2), identified as "drug-free air"). Self-reported and psychomotor effects were measured at various times. Dose-response functions varied across subjects and included bitonic, monotonic increasing, monotonic decreasing, U-shaped, and flat dose-response functions for reinforcing and/or self-reported effects. For subjects who showed bitonic reinforcing effects, the descending limb of the dose-response function could not be attributed to behavioral impairment. This study replicates previous studies showing dose-dependent effects of N(2)O, as well as between-subject variability in N(2)O effects. Bitonic dose-response functions for some subjects extend the generality of the phenomenon of bitonicity of drug effects to N(2)O effects in humans.
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Affiliation(s)
- Diana J Walker
- Department of Anesthesia and Critical Care, The University of Chicago, 5841 South Maryland Avenue, MC 4028, Chicago, IL 60637, USA.
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Ramsay DS, Watson CH, Leroux BG, Prall CW, Kaiyala KJ. Conditioned place aversion and self-administration of nitrous oxide in rats. Pharmacol Biochem Behav 2003; 74:623-33. [PMID: 12543228 DOI: 10.1016/s0091-3057(02)01048-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The rewarding/aversive effects of nitrous oxide (N(2)O) were evaluated using the place conditioning paradigm. Male Long-Evans rats (N=103) received a daily 40-min gas exposure for 8 consecutive days that alternated between two distinct chambers. A control group received placebo gas in both chamber types, while the N(2)O groups (8%, 15%, 30%, and 60% N(2)O) received four consistent pairings of N(2)O with one chamber type and four pairings of placebo gas with the other. A conditioned place aversion was found for the chambers that had been paired with 30% and 60% N(2)O. Place aversions were demonstrated during a 20-min test session on Day 9 when placebo gas was delivered to both chambers, and also during a 20-min test session on Day 10 when N(2)O was delivered to both chambers. A second study evaluated two novel methods of inhalant self-administration, one that used a forced-choice alternating gas environment and one that used a free-choice paradigm. Of four rats tested, two self-administered N(2)O, one rat avoided N(2)O, and one rat's behavior was consistent with neither self-administration nor avoidance. Availability of these methods will facilitate research on the neurobiological mechanisms underlying the rewarding and reinforcing effects of N(2)O and other abused inhalants.
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Affiliation(s)
- Douglas S Ramsay
- Department of Pediatric Dentistry, University of Washington, Box # 357136, Seattle, WA 98195-7136, USA.
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Walker DJ, Zacny JP. Analysis of the reinforcing and subjective effects of different doses of nitrous oxide using a free-choice procedure. Drug Alcohol Depend 2002; 66:93-103. [PMID: 11850141 DOI: 10.1016/s0376-8716(01)00188-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reinforcing and subjective effects of five doses of nitrous oxide (0, 10, 20, 30, 40% N(2)O in O(2)) were studied in 20 non-drug-abusers using a free-choice procedure. During each of five sessions, subjects sampled a dose of N(2)O and 100% O(2) (placebo) for 10 min each. Later they chose nine times, once every 5 min, among N(2)O (e.g. 'Agent A'), placebo (e.g. 'Agent B'), or a no-drug option. Mean preference ratios (N(2)O choices/[N(2)O choices+placebo choices]) and total N(2)O choice increased with increasing N(2)O dose. Individual preference ratios suggested that at least one active dose of N(2)O functioned as a reinforcer in 80% of subjects, and the doses that functioned as reinforcers varied across subjects. N(2)O choice was positively correlated with end-of-session and post-session ratings of N(2)O liking and of wanting to inhale N(2)O again, but not with ratings of those effects during sampling. Placebo was chosen significantly less than the no-drug option, even though both were 100% O(2). More robust reinforcing effects of N(2)O were observed in this subject population than in previous studies. Choice data emphasize the importance of examining a range of doses, and of examining those effects within-subject, when assessing reinforcing effects of drugs. Inclusion of the no-drug option eliminated the 'forced' choice of placebo, making preference ratios easier to interpret than in previous, forced-choice procedures. Reinforcing effects were more correlated with subjective effects assessed after the session than with subjective effects obtained while subjects were under the influence of the drug.
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Affiliation(s)
- Diana J Walker
- Department of Anesthesia & Critical Care, The University of Chicago, 5841 S. Maryland Ave., MC 4028, Chicago, IL 60637, USA.
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