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Song M, Qiang Y, Wang S, Shan S, Zhang L, Liu C, Song F, Zhao X. High-fat diet exacerbates 1-Bromopropane-induced loss of dopaminergic neurons in the substantia nigra of mice through mitochondrial damage associated necroptotic pathway. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 276:116280. [PMID: 38574648 DOI: 10.1016/j.ecoenv.2024.116280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 03/25/2024] [Accepted: 03/30/2024] [Indexed: 04/06/2024]
Abstract
In recent years, accumulating evidence supports that occupational exposure to solvents is associated with an increased incidence of Parkinson's disease (PD) among workers. The neurotoxic effects of 1-bromopropane (1-BP), a widely used new-type solvent, are well-established, yet data on its relationship with the etiology of PD remain limited. Simultaneously, high-fat consumption in modern society is recognized as a significant risk factor for PD. However, whether there is a synergistic effect between a high-fat diet and 1-BP exposure remains unclear. In this study, adult C57BL/6 mice were fed either a chow or a high-fat diet for 18 weeks prior to 12-week 1-BP treatment. Subsequent neurobehavioral and neuropathological examinations were conducted to assess the effects of 1-BP exposure on parkinsonian pathology. The results demonstrated that 1-BP exposure produced obvious neurobehavioral abnormalities and dopaminergic degeneration in the nigral region of mice. Importantly, a high-fat diet further exacerbated the impact of 1-BP on motor and cognitive abnormalities in mice. Mechanistic investigation revealed that mitochondrial damage and mtDNA release induced by 1-BP and high-fat diet activate NLRP3 and cGAS-STING pathway- mediated neuroinflammatory response, and ultimately lead to necroptosis of dopaminergic neurons. In summary, our study unveils a potential link between chronic 1-BP exposure and PD-like pathology with motor and no-motor defects in experimental animals, and long-term high-fat diet can further promote 1-BP neurotoxicity, which underscores the pivotal role of environmental factors in the etiology of PD.
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Affiliation(s)
- Mingxue Song
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Yalong Qiang
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Shuai Wang
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Shan Shan
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Liwen Zhang
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Caipei Liu
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Fuyong Song
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Xiulan Zhao
- Department of Health Toxicology and Nutrition, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China.
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The Effects of the Inhalant Toluene on Cognitive Function and Behavioral Flexibility: A Review of Recent Findings. ADDICTION NEUROSCIENCE 2023; 5:100059. [PMID: 36798693 PMCID: PMC9928149 DOI: 10.1016/j.addicn.2022.100059] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Substance use disorder (SUD) is characterized, in part, by lack of control over drug seeking and taking. The prefrontal cortex (PFC) is highly involved in control of behavior and deficits in PFC structure and function have been demonstrated in clinical and preclinical studies of SUD. Of the various classes of drugs associated with the development of SUD, inhalants are among the least studied despite their widespread use among adolescents and children. In this work, we review what is currently known regarding the sites and mechanisms of action of inhalants with a focus on the volatile solvent toluene that is contained in a wide variety of legal and easily obtained products. We then describe how inhalants including toluene affect various behaviors with an emphasis on those associated with PFC function and how chronic use of inhalants alters brain structure and neuronal signaling. Findings from these studies highlight advances made in recent years that have expanded our understanding of the effects of inhalants on brain structure and reinforce the need for continued work in this field.
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Zhang W, Xiong BR, Zhang LQ, Huang X, Yuan X, Tian YK, Tian XB. The Role of the GABAergic System in Diseases of the Central Nervous System. Neuroscience 2021; 470:88-99. [PMID: 34242730 DOI: 10.1016/j.neuroscience.2021.06.037] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/27/2021] [Accepted: 06/28/2021] [Indexed: 12/20/2022]
Abstract
It is well known that the central nervous system (CNS) is a complex neuronal network and its function depends on the balance between excitatory and inhibitory neurons. Disruption of the excitatory/inhibitory (E/I) balance is the main cause for the majority of the CNS diseases. In this review, we will discuss roles of the inhibitory system in the CNS diseases. The GABAergic system as the main inhibitory system, is essential for the appropriate functioning of the CNS, especially as it is engaged in the formation of learning and memory. Many researchers have reported that the GABAergic system is involved in regulating synaptic plasticity, cognition and long-term potentiation. Some clinical manifestations (such as cognitive dysfunctions, attention deficits, etc.) have also been shown to emerge after abnormalities in the GABAergic system accompanied with concomitant diseases, that include Alzheimer's disease (AD), Parkinson's disease (PD), Autism spectrum disorder (ASD), Schizophrenia, etc. The GABAergic system consists of GABA, GABA transporters, GABAergic receptors and GABAergic neurons. Changes in any of these components may contribute to the dysfunctions of the CNS. In this review, we will synthesize studies which demonstrate how the GABAergic system participates in the pathogenesis of the CNS disorders, which may provide a new idea that might be used to treat the CNS diseases.
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Affiliation(s)
- Wen Zhang
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, Hubei, China
| | - Bing-Rui Xiong
- Department of Anesthesiology, Zhongnan Hospital, Wuhan University, East Lake Road, 430071 Wuhan, Hubei, China
| | - Long-Qing Zhang
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, Hubei, China
| | - Xian Huang
- Department of Physiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, Hubei, China
| | - Xiaoman Yuan
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, Hubei, China
| | - Yu-Ke Tian
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, Hubei, China
| | - Xue-Bi Tian
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, Hubei, China.
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Cruz SL, Bowen SE. The last two decades on preclinical and clinical research on inhalant effects. Neurotoxicol Teratol 2021; 87:106999. [PMID: 34087382 DOI: 10.1016/j.ntt.2021.106999] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/24/2021] [Accepted: 05/18/2021] [Indexed: 12/21/2022]
Abstract
This paper reviews the scientific evidence generated in the last two decades on the effects and mechanisms of action of most commonly misused inhalants. In the first section, we define what inhalants are, how they are used, and their prevalence worldwide. The second section presents specific characteristics that define the main groups of inhalants: (a) organic solvents; (b) aerosols, gases, and volatile anesthetics; and (c) alkyl nitrites. We include a table with the molecular formula, structure, synonyms, uses, physicochemical properties and exposure limits of representative compounds within each group. The third and fourth sections review the direct acute and chronic effects of common inhalants on health and behavior with a summary of mechanisms of action, respectively. In the fifth section, we address inhalant intoxication signs and available treatment. The sixth section examines the health effects, intoxication, and treatment of nitrites. The seventh section reviews current intervention strategies. Finally, we propose a research agenda to promote the study of (a) solvents other than toluene; (b) inhalant mixtures; (c) effects in combination with other drugs of abuse; (d) age and (e) sex differences in inhalant effects; (f) the long-lasting behavioral effects of animals exposed in utero to inhalants; (g) abstinence signs and neurochemical changes after interrupting inhalant exposure; (h) brain networks involved in inhalant effects; and finally (i) strategies to promote recovery of inhalant users.
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Affiliation(s)
- Silvia L Cruz
- Department of Pharmacobiology, Center of Research and Advanced Studies (Cinvestav), Calzada de los Tenorios No. 235, Col. Granjas Coapa, México City 14330, México.
| | - Scott E Bowen
- Department of Psychology, Wayne State University, 5057 Woodward Ave., Suite 7906.1, Detroit, MI 48202, USA.
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Delta-opioid receptor-mediated modulation of excitability of individual hippocampal neurons: mechanisms involved. Pharmacol Rep 2020; 73:85-101. [PMID: 33161533 DOI: 10.1007/s43440-020-00183-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 10/22/2020] [Accepted: 10/24/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Delta-opioid receptor (DOR)-mediated modulation of hippocampal neural networks is involved in emotions, cognition, and in pathophysiology and treatment of mood disorders. In this study, we examined the effects of DOR agonist (SNC80) and antagonist (naltrindole) on the excitability of individual hippocampal neurons. METHODS Primary neuronal cultures were prepared from hippocampi of newborn rats and cultivated in vitro for 8-14 days (DIV8-14). The effects of SNC80 naltrindole on evoked and spontaneous action potentials (APs) were measured at DIV8-9 and DIV13-14, respectively. RESULTS SNC80 (100 µM) potentiated spontaneous AP firing and stimulated sodium current; naltrindole had opposite effects. The stimulatory effect of 100 µM of SNC80 was revoked by pre-administration of 1 µM of naltrindole. SNC80 and naltrindole induced similar inhibitory effects on the evoked AP firing and on the calcium current. Further, SNC80 inhibited both peak and sustained potassium currents. Naltrindole had no effect on potassium currents. CONCLUSION We suggest that the effects of naltrindole and high concentration of SNC80 on the sodium currents are mediated via DORs and underlying the changes in spontaneous activity. The inhibitory effects of SNC80 on calcium and potassium currents might also be DOR-dependent; these currents might mediate SNC80 effect on the evoked AP firing. The inhibitory effects of naltrindole on calcium and of low doses of SNC80 on sodium currents might be however DOR independent. The behavioral effects of SNC80 and naltrindole, observed in previous studies, might be mediated, at least in part, via the modulatory effect of these ligands on the excitability of hippocampal neurons.
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Abstract
Inhalants are a loosely organized category of abused compounds defined entirely by their common route of administration. Inhalants include volatile solvents, fuels, volatile anesthetics, gasses, and liquefied refrigerants, among others. They are ubiquitous in modern society as ingredients in a wide variety of household, commercial, and medical products. Persons of all ages abuse inhalants but the highest prevalence of abuse is in younger adolescents. Although inhalants have been shown to act upon a host of neurotransmitter receptors, the stimulus effects of the few inhalants which have been trained or tested in drug discrimination procedures suggest that their discriminative stimulus properties are mediated by a few key neurotransmitter receptor systems. Abused volatile solvent inhalants have stimulus effects that are similar to a select group of GABAA positive modulators comprised of benzodiazepines and barbiturates. In contrast the stimulus effects of nitrous oxide gas appear to be at least partially mediated by uncompetitive antagonism of NMDA receptors. Finally, volatile anesthetic inhalants have stimulus effects in common with both GABAA positive modulators as well as competitive NMDA antagonists. In addition to a review of the pharmacology underlying the stimulus effects of inhalants, the chapter also discusses the scientific value of utilizing drug discrimination as a means of functionally grouping inhalants according to their abuse-related pharmacological properties.
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Affiliation(s)
- Keith L Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, 410 North 12th Street, Room 746, P.O. Box 980613, Richmond, VA, 23298-0613, USA.
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A novel approach of substitution therapy with inhalation of essential oil for the reduction of inhalant craving: A double-blinded randomized controlled trial. Psychiatry Res 2018; 261:61-67. [PMID: 29287237 DOI: 10.1016/j.psychres.2017.12.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 10/06/2017] [Accepted: 12/08/2017] [Indexed: 11/22/2022]
Abstract
Inhalants, which are neurotoxic central nervous system (CNS) suppressants, are frequently abused by young adults. Unlike other CNS depressants, including alcohol and opiates, no treatment is currently approved for inhalant dependence. In this report, a novel approach of substitution treatment for inhalant addiction was explored in a double-blinded, randomized, controlled crossover design to examine the effects of inhalation of essential oil and perfume on the reduction of cue-induced craving for inhalant in thirty-four Thai males with inhalant dependence. The craving response was measured by the modified version of Penn Alcohol Craving Score for Inhalants (PACS-inhalants). The participants (mean age ± SE = 27.9 ± 1.4) in this trial had used inhalant for 5.8 ± 1.1 years. Cravings could be induced in all participants by visual cues as assessed by ^50% increases in inhalant craving levels. Generalized estimating equations showed a significant suppressant effect of essential oil, but not perfume, on the craving response as compared with baseline cue-induced craving. Moreover, essential oil, but not perfume, had significant effects on physiological responses including decreasing pulse rate. It is concluded that inhaling essential oil as a substitution treatment for inhalant may be used as part of treatment programs for reducing inhalant craving.
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Nimitvilai S, You C, Arora DS, McElvain MA, Vandegrift BJ, Brodie MS, Woodward JJ. Differential Effects of Toluene and Ethanol on Dopaminergic Neurons of the Ventral Tegmental Area. Front Neurosci 2016; 10:434. [PMID: 27713687 PMCID: PMC5031606 DOI: 10.3389/fnins.2016.00434] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 09/07/2016] [Indexed: 11/13/2022] Open
Abstract
Drugs of abuse increase the activity of dopaminergic neurons of the ventral tegmental area (VTA), and output from the VTA is critical for both natural and drug-induced reward and reinforcement. Ethanol and the abused inhalant toluene both enhance VTA neuronal firing, but the mechanisms of this effect is not fully known. In this study, we used extracellular recordings to compare the actions of toluene and ethanol on DA VTA neurons. Both ethanol and toluene increased the firing rate of DA neurons, although toluene was ~100 times more potent than ethanol. The mixed ion channel blocker quinine (100 μM) blocked the increases in firing produced by ethanol and toluene, indicating some similarity in mechanisms of excitation. A mixture of antagonists of GABA and cholinergic receptors did not prevent toluene-induced or ethanol-induced excitation, and toluene-induced excitation was not altered by co-administration of ethanol, suggesting independent mechanisms of excitation for ethanol and toluene. Concurrent blockade of NMDA, AMPA, and metabotropic glutamate receptors enhanced the excitatory effect of toluene while having no significant effect on ethanol excitation. Nicotine increased firing of DA VTA neurons, and this was blocked by the nicotinic antagonist mecamylamine (1 μM). Mecamylamine did not alter ethanol or toluene excitation of firing but the muscarinic antagonist atropine (5 μM) or a combination of GABA antagonists (bicuculline and CGP35348, 10 μM each) reduced toluene-induced excitation without affecting ethanol excitation. The Ih current blocker ZD7288 abolished the excitatory effect of toluene but unlike the block of ethanol excitation, the effect of ZD7288 was not reversed by the GIRK channel blocker barium, but was reversed by GABA antagonists. These results demonstrate that the excitatory effects of ethanol and toluene have some similarity, such as block by quinine and ZD7288, but also indicate that there are important differences between these two drugs in their modulation by glutamatergic, cholinergic, and GABAergic receptors. These findings provide important information regarding the actions of abused inhalants on central reward pathways, and suggest that regulation of the activation of central dopamine pathways by ethanol and toluene partially overlap.
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Affiliation(s)
- Sudarat Nimitvilai
- Department of Neuroscience, Medical University of South Carolina Charleston, SC, USA
| | - Chang You
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
| | - Devinder S Arora
- School of Pharmacy, Griffith University Southport, QLD, Australia
| | - Maureen A McElvain
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
| | - Bertha J Vandegrift
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
| | - Mark S Brodie
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
| | - John J Woodward
- Department of Neuroscience, Medical University of South Carolina Charleston, SC, USA
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Wathier L, Venet T, Thomas A, Nunge H, Bonfanti E, Cosnier F, Parietti-Winkler C, Campo P, Tsan P, Bouguet-Bonnet S, Gansmüller A. Membrane fluidity does not explain how solvents act on the middle-ear reflex. Neurotoxicology 2016; 57:13-21. [PMID: 27565678 DOI: 10.1016/j.neuro.2016.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 07/26/2016] [Accepted: 08/03/2016] [Indexed: 10/21/2022]
Abstract
Some volatile aromatic solvents have similar or opposite effects to anesthetics in the central nervous system. Like for anesthetics, the mechanisms of action involved are currently the subject of debate. This paper presents an in vivo study to determine whether direct binding or effects on membrane fluidity best explain how solvents counterbalance anesthesia's depression of the middle-ear reflex (MER). Rats were anesthetized with a mixture of ketamine and xylazine while also exposed to solvent vapors (toluene, ethylbenzene, or one of the three xylene isomers) and the amplitude of their MER was monitored. The depth of anesthesia was standardized based on the magnitude of the contraction of the muscles involved in the MER, determined by measuring cubic distortion product oto-acoustic emissions (DPOAEs) while triggering the bilateral reflex with contralateral acoustic stimulation. The effects of the aromatic solvents were quantified based on variations in the amplitude of the DPOAEs. The amplitude of the alteration to the MER measured in anesthetized rats did not correlate with solvent lipophilocity (as indicated by logKow values). Results obtained with the three xylene isomers indicated that the positions of two methyl groups around the benzene ring played a determinant role in solvent/neuronal cell interaction. Additionally, Solid-state Nuclear Magnetic Resonance (NMR) spectra for brain microsomes confirmed that brain lipid fluidity was unaffected by solvent exposure, even after three days (6h/day) at an extremely high concentration (3000ppm). Therefore, aromatic solvents appear to act directly on the neuroreceptors involved in the acoustic reflex circuit, rather than on membrane fluidity. The affinity of this interaction is determined by stereospecific parameters rather than lipophilocity.
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Affiliation(s)
- Ludivine Wathier
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France
| | - Thomas Venet
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France
| | - Aurélie Thomas
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France
| | - Hervé Nunge
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France
| | - Elodie Bonfanti
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France
| | - Frédéric Cosnier
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France
| | | | - Pierre Campo
- Institut National de Recherche et de Sécurité, Rue du Morvan, F-54519 Vandoeuvre-les-Nancy, France.
| | - Pascale Tsan
- Université de Lorraine, CRM2, UMR 7036, Vandoeuvre-les-Nancy, F-54506, France; CNRS, CRM2, UMR 7036, Vandoeuvre-les-Nancy, F-54506, France
| | - Sabine Bouguet-Bonnet
- Université de Lorraine, CRM2, UMR 7036, Vandoeuvre-les-Nancy, F-54506, France; CNRS, CRM2, UMR 7036, Vandoeuvre-les-Nancy, F-54506, France
| | - Axel Gansmüller
- Université de Lorraine, CRM2, UMR 7036, Vandoeuvre-les-Nancy, F-54506, France; CNRS, CRM2, UMR 7036, Vandoeuvre-les-Nancy, F-54506, France
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Dick ALW, Pooters T, Gibbs S, Giles E, Qama A, Lawrence AJ, Duncan JR. NMDA receptor binding is reduced within mesocorticolimbic regions following chronic inhalation of toluene in adolescent rats. Brain Res 2015; 1624:239-252. [DOI: 10.1016/j.brainres.2015.07.037] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 07/21/2015] [Accepted: 07/23/2015] [Indexed: 11/16/2022]
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Kobald SO, Wascher E, Blaszkewicz M, Golka K, van Thriel C. Neurobehavioral and neurophysiological effects after acute exposure to a single peak of 200 ppm toluene in healthy volunteers. Neurotoxicology 2015; 48:50-9. [DOI: 10.1016/j.neuro.2015.03.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 03/04/2015] [Accepted: 03/04/2015] [Indexed: 10/23/2022]
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12
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Amadasi A, Mastroluca L, Marasciuolo L, Caligara M, Sironi L, Gentile G, Zoja R. Death due to acute tetrachloroethylene intoxication in a chronic abuser. Int J Legal Med 2015; 129:487-93. [DOI: 10.1007/s00414-015-1143-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 01/09/2015] [Indexed: 10/24/2022]
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13
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Bryson EO. The Abuse of Agents Used to Induce or Maintain General Anesthesia: Intravenous Hypnotics and the Halogenated Hydrocarbons. Subst Abus 2015. [DOI: 10.1007/978-1-4939-1951-2_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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14
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Cadmium increases the sensitivity of adolescent female mice to nicotine-related behavioral deficits. Behav Neurol 2014; 2014:360978. [PMID: 25477708 PMCID: PMC4247978 DOI: 10.1155/2014/360978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 10/22/2014] [Indexed: 11/29/2022] Open
Abstract
This study investigates spatial and nonspatial working memory, anxiety related behavior, and motor activities in cadmium and/or nicotine exposed female adolescent mice. P28 female adolescent mice (albino strain) were divided into four groups of five (n = 5) mice each. A set of mice (Nic) received subcutaneous nicotine (2.0 mg/kg) while a separate set (Cd) was treated with 2.0 mg/kg cadmium (subcutaneous). For the combined treatments of cadmium and nicotine, we administered 2.0 mg/kg Nicotine and 2.0 mg/kg of Cd. Subsequently, a separate group of animals (n = 5; control) received normal saline. The total duration of treatment for all groups was 28 days (P28–P56). At P56, the treatment was discontinued, after which the animals were examined in behavioural tests. Nicotine and cadmium increased the metabolism and food intake in the female adolescent mice. This also corresponded to an increase in weight when compared with the control. However, a combined nicotine-cadmium treatment induced a decline in weight of the animals versus the control. Also, nicotine administration increased the motor function, while cadmium and nicotine-cadmium treatment caused a decline in motor activity. Both nicotine and cadmium induced a reduction in memory index; however, nicotine-cadmium treatment induced the most significant decrease in nonspatial working memory.
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Gmaz JM, McKay BE. Toluene decreases Purkinje cell output by enhancing inhibitory synaptic transmission in the cerebellar cortex. Neurosci Lett 2014; 560:1-6. [PMID: 24345417 DOI: 10.1016/j.neulet.2013.12.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 12/07/2013] [Accepted: 12/09/2013] [Indexed: 11/29/2022]
Abstract
Toluene belongs to a class of psychoactive drugs known as inhalants. Found in common household products such as adhesives, paint products, and aerosols, toluene is inhaled for its intoxicating and euphoric properties. Additionally, exposure to toluene disrupts motor behaviors in a manner consistent with impairments to cerebellar function. Previous work has suggested a role of GABA in mediating toluene's neurobehavioral effects, but how this manifests in the cerebellar cortex is not yet understood. In the present study, we examined the effects of toluene on cerebellar Purkinje cell action potential output and inhibitory synaptic transmission onto Purkinje cells using patch clamp electrophysiology in acute rat cerebellar slices. Toluene (1mM) reduced the frequency of Purkinje cell action potential output without affecting input resistance. Furthermore, toluene dose-dependently enhanced inhibitory synaptic transmission onto Purkinje cells, increasing the amplitude and frequency of inhibitory postsynaptic currents; no change in the frequency of action potentials from molecular layer interneurons was noted. The observed decreases in Purkinje cell action potential output could contribute to toluene-evoked impairments in cerebellar and motor functions.
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Affiliation(s)
- Jimmie M Gmaz
- Department of Psychology, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
| | - Bruce E McKay
- Department of Psychology, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.
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17
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Woodward JJ, Beckley J. Effects of the abused inhalant toluene on the mesolimbic dopamine system. ACTA ACUST UNITED AC 2014; 3. [PMID: 25360326 DOI: 10.4303/jdar/235838] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Toluene is a representative member of a class of inhaled solvents that are voluntarily used by adolescents and adults for their euphorigenic effects. Research into the mechanisms of action of inhaled solvents has lagged behind that of other drugs of abuse despite mounting evidence that these compounds exert profound neurobehavioral and neurotoxicological effects. Results from studies carried out by the authors and others suggest that the neural effects of inhalants arise from their interaction with a discrete set of ion channels that regulate brain activity. Of particular interest is how these interactions allow toluene and other solvents to engage portions of an addiction neurocircuitry that includes midbrain and cortical structures. In this review, we focus on the current state of knowledge regarding toluene's action on midbrain dopamine neurons, a key brain region involved in the initial assessment of natural and drug-induced rewards. Findings from recent studies in the authors' laboratory show that brief exposures of adolescent rats to toluene vapor induce profound changes in markers of glutamatergic plasticity in VTA DA neurons. These changes are restricted to VTA DA neurons that project to limbic structures and are prevented by transient activation of the medial prefrontal cortex prior to toluene exposure. Together, these data provide the first evidence linking the voluntary inhalation of solvents to changes in reward -sensitive dopamine neurons.
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Affiliation(s)
- John J Woodward
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425
| | - Jacob Beckley
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425 ; Department of Neurology, University of California - San Francisco, San Francisco, CA
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Shelton KL, Nicholson KL. Pharmacological classification of the abuse-related discriminative stimulus effects of trichloroethylene vapor. ACTA ACUST UNITED AC 2014; 3:235839. [PMID: 25202471 DOI: 10.4303/jdar/235839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Inhalants are distinguished as a class primarily based upon a shared route of administration. Grouping inhalants according to their abuse-related in vivo pharmacological effects using the drug discrimination procedure has the potential to provide a more relevant classification scheme to the research and treatment community. Mice were trained to differentiate the introceptive effects of the trichloroethylene vapor from air using an operant procedure. Trichloroethylene is a chlorinated hydrocarbon solvent once used as an anesthetic as well as in glues and other consumer products. It is now primarily employed as a metal degreaser. We found that the stimulus effects of trichloroethylene were similar to those of other chlorinated hydrocarbon vapors, the aromatic hydrocarbon toluene and the vapor anesthetics methoxyflurane and isoflurane. The stimulus effects of trichloroethylene overlapped with those of the barbiturate methohexital, to a lesser extent the benzodiazepine midazolam and to ethanol. NMDA antagonists, the kappa opioid agonist U50,488 and the mixed 5-HT agonist mCPP largely failed to substitute for trichloroethylene. These data suggest that stimulus effects of chlorinated hydrocarbon vapors are mediated at least partially by GABAA receptor positive modulatory effects.
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Affiliation(s)
- Keith L Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, P.O. Box 980613, Richmond, Virginia 23298-0613
| | - Katherine L Nicholson
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, P.O. Box 980613, Richmond, Virginia 23298-0613
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Scott KD, Scott AA. Adolescent inhalant use and executive cognitive functioning. Child Care Health Dev 2014; 40:20-8. [PMID: 23551203 DOI: 10.1111/cch.12052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/22/2013] [Indexed: 11/29/2022]
Abstract
BACKGROUND This study investigates the association between inhalant use and executive cognitive functioning (ECF) and processing speed (PS) in 754 adjudicated poly-substance users on a series of neuropsychological tests. Poly-substance users who used inhalants (PSI = 262) and poly-substance users who did not use inhalants (PSO = 492) neuropsychological tests scores were compared. Hispanic Americans comprised 72% of the participants; European Americans, African Americans and Asian Americans comprised 28% of the participants. METHODS Standardized neuropsychological tests were used to assess ECF and PS. Psychosocial and substance abuse standardized surveys were used to assess drug use severity and psychosocial problems associated with substance use. RESULTS Multiple Analysis of Covariance shows that PSI users who used inhalants performed worse on ECF and PS measures in comparison to non-inhalant poly-substance users (PSO). PSI users were younger, used more drugs and had more psychiatric admissions than PSO users. CONCLUSION PSI users initiate substances at a younger age and experienced more ECF and PS deficits, and behavioural problems in comparison to PSO users. The results of this study suggest that PS has direct effect on ECF and psychosocial outcomes in PSI users.
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Affiliation(s)
- K D Scott
- Department of Counseling Psychology, University of Texas, San Antonio, TX, USA
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Cruz SL, Rivera-García MT, Woodward JJ. Review of toluene action: clinical evidence, animal studies and molecular targets. ACTA ACUST UNITED AC 2014; 3. [PMID: 25360325 DOI: 10.4303/jdar/235840] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
It has long been known that individuals will engage in voluntary inhalation of volatile solvents for their rewarding effects. However, research into the neurobiology of these agents has lagged behind that of more commonly used drugs of abuse such as psychostimulants, alcohol and nicotine. This imbalance has begun to shift in recent years as the serious effects of abused inhalants, especially among children and adolescents, on brain function and behavior have become appreciated and scientifically documented. In this review, we discuss the physicochemical and pharmacological properties of toluene, a representative member of a large class of organic solvents commonly used as inhalants. This is followed by a brief summary of the clinical and pre-clinical evidence showing that toluene and related solvents produce significant effects on brain structures and processes involved in the rewarding aspects of drugs. This is highlighted by tables highlighting toluene's effect on behaviors (reward, motor effects, learning, etc.) and cellular proteins (e.g. voltage and ligand-gated ion channels) closely associated the actions of abused substances. These sections demonstrate not only the significant progress that has been made in understanding the neurobiological basis for solvent abuse but also reveal the challenges that remain in developing a coherent understanding of this often overlooked class of drugs of abuse.
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Affiliation(s)
- Silvia L Cruz
- Departamento de Farmacobiología, Cinvestav, México, D.F., University of South Carolina, Charleston, SC
| | | | - John J Woodward
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC
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Beckley JT, Woodward JJ. Volatile solvents as drugs of abuse: focus on the cortico-mesolimbic circuitry. Neuropsychopharmacology 2013; 38:2555-67. [PMID: 23954847 PMCID: PMC3828545 DOI: 10.1038/npp.2013.206] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/12/2013] [Accepted: 08/13/2013] [Indexed: 12/15/2022]
Abstract
Volatile solvents such as those found in fuels, paints, and thinners are found throughout the world and are used in a variety of industrial applications. However, these compounds are also often intentionally inhaled at high concentrations to produce intoxication. While solvent use has been recognized as a potential drug problem for many years, research on the sites and mechanisms of action of these compounds lags behind that of other drugs of abuse. In this review, we first discuss the epidemiology of voluntary solvent use throughout the world and then consider what is known about their basic pharmacology and how this may explain their use as drugs of abuse. We next present data from preclinical and clinical studies indicating that these substances induce common addiction sequelae such as dependence, withdrawal, and cognitive impairments. We describe how toluene, the most commonly studied psychoactive volatile solvent, alters synaptic transmission in key brain circuits such as the mesolimbic dopamine system and medial prefrontal cortex (mPFC) that are thought to underlie addiction pathology. Finally, we make the case that activity in mPFC circuits is a critical regulator of the mesolimbic dopamine system's ability to respond to volatile solvents like toluene. Overall, this review provides evidence that volatile solvents have high abuse liability because of their selective effects on critical nodes of the addiction neurocircuitry, and underscores the need for more research into how these compounds induce adaptations in neural circuits that underlie addiction pathology.
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Affiliation(s)
- Jacob T Beckley
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA,Center for Drug and Alcohol Programs, Department of Psychiatry/Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - John J Woodward
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA,Center for Drug and Alcohol Programs, Department of Psychiatry/Neurosciences, Medical University of South Carolina, Charleston, SC, USA,Department of Neurosciences, Medical University of South Carolina, IOP 4 North, 67 President Street, MSC 861, Charleston, SC 29425, USA, Tel: +(843) 792 5225, Fax: +(843) 792 7353, E-mail:
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Duncan JR, Lawrence AJ. Conventional Concepts and New Perspectives for Understanding the Addictive Properties of Inhalants. J Pharmacol Sci 2013; 122:237-43. [DOI: 10.1254/jphs.13r04cp] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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Campo P, Venet T, Thomas A, Cour C, Castel B, Nunge H, Cosnier F. Inhaled toluene can modulate the effects of anesthetics on the middle-ear acoustic reflex. Neurotoxicol Teratol 2012. [PMID: 23183362 DOI: 10.1016/j.ntt.2012.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Toluene (Tol) is an organic solvent widely used in the industry. It is also abused as an inhaled solvent, and can have deleterious effects on hearing. Recently, it was demonstrated that Tol has both anticholinergic and antiglutamatergic effects, and that it also inhibits voltage-dependent Ca(2+) channels. This paper describes a study of the effects of inhaled Tol on rats anesthetized with isoflurane, pentobarbital, or a mixture of ketamine/xylazine. Hearing was tested using distortion product oto-acoustic emissions (DPOAEs) associated with a contralateral noise to evaluate contraction of the middle-ear muscles. This allowed us to assess the interactions between the effects of Tol and anesthesia on the central nervous system (CNS). Although both anesthetics and Tol are known to inhibit the middle-ear acoustic reflex, our data indicated that inhaled Tol counterbalances the effects of anesthetic in a dose-dependent manner. In other terms, Tol can increase the amplitude of the middle-ear reflex in anesthetized rats, whatever the nature of the anesthetic used. This indicates that inhaling Tol (a Ca(2+)-channel-blocking drug) modifies the potency of anesthesia, and thereby the amplitude of the middle-ear reflex.
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Affiliation(s)
- Pierre Campo
- Institut National de Recherche et de Sécurité, Vandœuvre Cedex, France.
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Volatile substance misuse : clinical considerations, neuropsychopharmacology and potential role of pharmacotherapy in management. CNS Drugs 2012; 26:927-35. [PMID: 23018545 DOI: 10.1007/s40263-012-0001-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Volatile substance misuse is among the most prevalent and toxic forms of psychoactive drug use, and often results in highly deleterious social, psychological and medical consequences. The prevalence of this pernicious form of substance misuse owes in part to the fact that volatile substances of misuse are ubiquitous in the natural environment. Commonly misused commercial products include glue, shoe polish, nail polish remover, butane lighter fluid, gasoline and computer duster spray. National samples of volatile substance misusers tend to exhibit high rates of psychiatric problems and antisocial behaviour. In addition, cognitive impairments and affective dysregulation are often observed among these individuals. Volatile substances exert their complex neuropharmacological effects on dopaminergic, glutamatergic, GABAergic and serotoninergic receptor systems, as well as on cell membranes and ion channels. Concomitantly, pharmacotherapies for volatile substance abuse might profitably target a number of mechanisms, including reward circuitry in the brain, symptoms of craving and withdrawal, neuropsychiatric and emotional impairments that promote volatile substance abuse, and cognitive enhancement to rectify deficits in executive function. This review details the modes of use, subjective effects, epidemiology, adverse consequences, neuropsychopharmacology and drug treatment of volatile substance misuse, and discusses the potential role of novel forms of pharmacological intervention for this oft-overlooked public health threat of epidemic proportions.
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Paez-Martinez N, Aldrete-Audiffred J, Gallardo-Tenorio A, Castro-Garcia M, Estrada-Camarena E, Lopez-Rubalcava C. Participation of GABAA, GABA(B) receptors and neurosteroids in toluene-induced hypothermia: evidence of concentration-dependent differences in the mechanism of action. Eur J Pharmacol 2012; 698:178-85. [PMID: 23085024 DOI: 10.1016/j.ejphar.2012.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 09/21/2012] [Accepted: 10/06/2012] [Indexed: 12/12/2022]
Abstract
Toluene is a misused substance that modifies γ-aminobutyric acid (GABA) release and shares behavioral and molecular effects with GABA(A) and GABA(B) receptor agonists. GABAergic compounds are involved in thermoregulation processes and volatile substance users have reported that one of the reasons to inhale is to avoid feeling cold. At present, no studies have analyzed the effects of inhalants on body temperature and the mechanism of action involved. Thus, the main purpose of this study was to evaluate the effects of a (60 min) acute toluene inhalation (2000, 4000 and 6000 ppm) in core temperature. In addition, we tried to prevent the changes of temperature induced by toluene with the specific GABA(A) receptor blockers picrotoxin (0.01-0.1mg/kg), bicuculline (0.1-0.3mg/kg), and flumazenil (3-30 mg/kg); the GABA(B) receptor antagonist phaclofen (10-30 mg/kg) and the neurosteroid synthesis inhibitor finasteride (10-30 mg/kg). Results show that toluene reduced core temperature in mice in a concentration-dependent manner. The hypothermia produced by 4000 ppm toluene was prevented by picrotoxin, bicuculline, phaclofen and finasteride but not by flumazenil. In contrast none of these antagonists tested blocked the effects of 6000 ppm toluene. In conclusion, toluene decreases core temperature, GABA receptors and neurosteroids participate in toluene's action at 4000 ppm; but other mechanisms of action are involved in the hypothermic effects of 6000 ppm toluene.
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Affiliation(s)
- Nayeli Paez-Martinez
- Sección de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, Col. Santo Tomás, CP 11340 Mexico City, Mexico.
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Conti AC, Lowing JL, Susick LL, Bowen SE. Investigation of calcium-stimulated adenylyl cyclases 1 and 8 on toluene and ethanol neurobehavioral actions. Neurotoxicol Teratol 2012; 34:481-8. [PMID: 22789433 DOI: 10.1016/j.ntt.2012.06.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 06/25/2012] [Accepted: 06/29/2012] [Indexed: 11/26/2022]
Abstract
The abused inhalant toluene has potent behavioral effects, but only recently has progress been made in understanding the molecular pathways that mediate the action of toluene in the brain. Toluene and ethanol induce similar behavioral effects and share some targets including NMDA and GABA receptors. In studies examining neuronal actions of ethanol, mice lacking the calcium-stimulated adenylyl cyclases (ACs), AC1 and AC8 (DKO), show increased sedation durations and impaired protein kinase A (PKA) phosphorylation following acute ethanol treatment. Therefore, using DKO mice, we compared the neurobehavioral responses following toluene exposure to that of ethanol exposure to determine if these abused substances share molecular mechanisms of action. In the present study, acute sensitivity to toluene- or ethanol-induced changes in locomotor activity was evaluated in DKO and wild type (WT) mice. Mice were exposed to toluene vapor (0, 500, 1000, 2000, 6000, or 8000ppm) for 30min in static exposure chambers equipped with activity monitors. Both WT and DKO mice demonstrated increased ambulatory distance during exposure to a 2000-ppm concentration of toluene compared to respective air-exposed (0ppm) controls. Significant increases in locomotor activity were also observed during an air-only recovery period following toluene exposure in WT and DKO mice that had been exposed to 2000ppm of toluene compared to respective air controls. Sedative effects of toluene were equivalent in WT and DKO mice, both during exposure and afterwards during recovery. Although no significant differences in locomotor activity were detected in DKO compared to WT mice at individual doses tested, a significant main effect of toluene was achieved, with DKO mice demonstrating a generalized reduction in locomotor activity during the post-toluene recovery period compared to WT mice (when analyzing all doses collectively). For comparison to toluene, additional WT and DKO mice were treated with 1.0 or 2.0g/kg ethanol (i.p.) and monitored for locomotor activation. In WT mice, both doses of ethanol increased distance traveled compared to saline controls. Conversely, DKO mice demonstrated no increase in locomotor activation at 1.0g/kg, with significantly reduced distances traveled at both doses compared to ethanol-treated WT mice. These behavioral activity results suggest that acute effects of ethanol and toluene are distinct in the mechanisms by which they induce acute sedating effects with respect to AC1 and AC8 activity, but may be similar in the mechanisms subserving locomotor stimulation.
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Affiliation(s)
- Alana C Conti
- John D. Dingell VA Medical Center, Detroit, MI 48201, USA.
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Gmaz JM, Matthews BA, McKay BE. Toluene inhalation modulates dentate gyrus granule cell output in vivo. Neurotoxicol Teratol 2012; 34:403-12. [DOI: 10.1016/j.ntt.2012.04.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 04/30/2012] [Accepted: 04/30/2012] [Indexed: 01/10/2023]
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GABAA-positive modulator selective discriminative stimulus effects of 1,1,1-trichloroethane vapor. Drug Alcohol Depend 2012; 121:103-9. [PMID: 21924562 PMCID: PMC3257377 DOI: 10.1016/j.drugalcdep.2011.08.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 08/17/2011] [Accepted: 08/18/2011] [Indexed: 11/22/2022]
Abstract
BACKGROUND The abuse-related behavioral effects of inhalant vapors are poorly understood but probably involve multiple neurotransmitter receptor mechanisms. The present study examined the receptor systems responsible for transducing the discriminative stimulus of the abused chlorinated hydrocarbon 1,1,1-trichloroethane (TCE) in mice. METHODS Thirty mice were trained to discriminate 10 min of 12,000 ppm TCE vapor exposure from air using an operant procedure. Substitution tests were then conduced with positive GABA(A) receptor modulators and/or NMDA receptor antagonists. RESULTS The nonselective benzodiazepines midazolam and diazepam produced 62% and 61% and the barbiturate pentobarbital produced 68% TCE-lever selection. Zaleplon, an alpha1 subunit-preferring positive GABA(A) receptor benzodiazepine-site positive modulator resulted in 29% TCE-lever selection. The direct extrasynaptic GABA(A) agonist gaboxodol (THIP) and the GABA reuptake inhibitor tiagabine failed to substitute for TCE. No substitution was elicited by a competitive (CGS-19755), noncompetitive (dizocilpine) or glycine-site (L701,324) NMDA antagonist. The mixed benzodiazepine/noncompetitive NMDA antagonist anesthetic Telazol and the anticonvulsant valproic acid exhibited low levels of partial substitution for TCE (38% and 39%, respectively). Ethanol and nitrous oxide failed to substitute for TCE. CONCLUSIONS The results suggest that the discriminative stimulus effects of TCE are fairly selectively mediated by positive modulation of GABA(A) receptors. The failure of gaboxadol to substitute and the poor substitution by zaleplon suggests that extrasynaptic GABA(A) receptors as well as GABA(A) receptors containing alpha1 subunits and are not involved in transducing the discriminative stimulus of TCE. Studies with additional GABA(A) benzodiazepine-site positive modulators will be necessary to confirm and extend these findings.
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Perit KE, Gmaz JM, Caleb Browne J, Matthews BA, Dunn MBF, Yang L, Raaphorst T, Mallet PE, McKay BE. Distribution of c-Fos immunoreactivity in the rat brain following abuse-like toluene vapor inhalation. Neurotoxicol Teratol 2012; 34:37-46. [DOI: 10.1016/j.ntt.2011.10.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 10/22/2011] [Accepted: 10/24/2011] [Indexed: 11/28/2022]
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The abused inhalant toluene differentially modulates excitatory and inhibitory synaptic transmission in deep-layer neurons of the medial prefrontal cortex. Neuropsychopharmacology 2011; 36:1531-42. [PMID: 21430649 PMCID: PMC3096820 DOI: 10.1038/npp.2011.38] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Volatile organic solvents such as toluene are voluntarily inhaled for their intoxicating effects. Solvent use is especially prevalent among adolescents, and is associated with deficits in a wide range of cognitive tasks including attention, behavioral control, and risk assessment. Despite these findings, little is known about the effects of toluene on brain areas mediating these behaviors. In this study, whole-cell patch-clamp recordings were used to determine the effect toluene on neurons within the medial PFC, a region critically involved in cognitive function. Toluene had no effect on measures of intrinsic excitability, but enhanced stimulus-evoked γ-amino butyric acid A-mediated inhibitory postsynaptic currents (IPSCs). In the presence of tetrodotoxin (TTX) to block action potentials, toluene increased the frequency and amplitude of miniature IPSCs. In contrast, toluene induced a delayed but persistent decrease in evoked or spontaneous AMPA-mediated excitatory postsynaptic currents (EPSCs). This effect was prevented by an intracellular calcium chelator or by the ryanodine receptor and SERCA inhibitors, dantrolene or thapsigargin, respectively, suggesting that toluene may mobilize intracellular calcium pools. The toluene-induced reduction in AMPA EPSCs was also prevented by a cannabinoid receptor (CB1R) antagonist, and was occluded by the CB1 agonist WIN 55,212-2 that itself induced a profound decrease in AMPA-mediated EPSCs. Toluene had no effect on the frequency or amplitude of miniature EPSCs recorded in the presence of TTX. Finally, toluene dose-dependently inhibited N-methyl-D-aspartate (NMDA)-mediated EPSCs and the magnitude and reversibility of this effect was CB1R sensitive indicating both direct and indirect actions of toluene on NMDA-mediated responses. Together, these results suggest that the effect of toluene on cognitive behaviors may result from its action on inhibitory and excitatory synaptic transmission of PFC neurons.
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Binge toluene exposure alters glutamate, glutamine and GABA in the adolescent rat brain as measured by proton magnetic resonance spectroscopy. Drug Alcohol Depend 2011; 115:101-6. [PMID: 21126832 PMCID: PMC3071441 DOI: 10.1016/j.drugalcdep.2010.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 09/07/2010] [Accepted: 11/01/2010] [Indexed: 12/23/2022]
Abstract
Despite the high incidence of toluene abuse in adolescents, little is known regarding the effect of binge exposure on neurochemical profiles during this developmental stage. In the current study, the effects of binge toluene exposure during adolescence on neurotransmitter levels were determined using high-resolution proton magnetic resonance spectroscopy ex vivo at 11.7T. Adolescent male Sprague-Dawley rats were exposed to toluene (0, 8000, or 12,000 ppm) for 15 min twice daily from postnatal day 28 (P28) through P34 and then euthanized either 1 or 7 days later (on P35 or P42) to assess glutamate (GLU), glutamine, and GABA levels in intact tissue punches from the medial prefrontal cortex (mPFC), anterior striatum and hippocampus. In the mPFC, toluene reduced GLU 1 day after exposure, with no effect on GABA, while after 7 days, GLU was no longer affected but there was an increase in GABA levels. In the hippocampus, neither GABA nor GLU was altered 1 day after exposure, whereas 7 days after exposure, increases were observed in GABA and GLU. Striatal GLU and GABA levels measured after either 1 or 7 days were not altered after toluene exposure. These findings show that 1 week of binge toluene inhalation selectively alters these neurotransmitters in the mPFC and hippocampus in adolescent rats, and that some of these effects endure at least 1 week after the exposure. The results suggest that age-dependent, differential neurochemical responses to toluene may contribute to the unique behavioral patterns associated with drug abuse among older children and young teens.
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Abstract
The fundamental principle that unites addictive drugs appears to be that each enhances synaptic dopamine by means that dissociate it from normal behavioral control, so that they act to reinforce their own acquisition. This occurs via the modulation of synaptic mechanisms that can be involved in learning, including enhanced excitation or disinhibition of dopamine neuron activity, blockade of dopamine reuptake, and altering the state of the presynaptic terminal to enhance evoked over basal transmission. Amphetamines offer an exception to such modulation in that they combine multiple effects to produce nonexocytic stimulation-independent release of neurotransmitter via reverse transport independent from normal presynaptic function. Questions about the molecular actions of addictive drugs, prominently including the actions of alcohol and solvents, remain unresolved, but their ability to co-opt normal presynaptic functions helps to explain why treatment for addiction has been challenging.
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Affiliation(s)
- David Sulzer
- Departments of Psychiatry, Neurology, and Pharmacology, Columbia University Medical Center, Black 308, 650 W. 168 St., New York, NY 10032, USA.
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Cruz SL. The latest evidence in the neuroscience of solvent misuse: an article written for service providers. Subst Use Misuse 2011; 46 Suppl 1:62-7. [PMID: 21609148 DOI: 10.3109/10826084.2011.580215] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This work reviews preclinical and clinical studies published during the past two decades on the cellular and behavioral effects of commonly misused solvents. In animals, acute solvent exposure produces motor impairment and antidepressant- and anxiolytic-like effects. Human intoxication from misusing solvents is similar to that of ethanol; however, hallucinations and sudden sniffing death may occur at high solvent concentrations. Among chronic misusers, there is evidence of impaired memory, increased prevalence of psychiatric disorders, and neurological damage. Solvents facilitate inhibitory neurotransmission and block excitatory mechanisms. Toluene, in particular, increases brain dopamine levels and its effects occur at concentrations that do not dissolve cell membranes; therefore, neuronal damage is not an immediate, unavoidable consequence of solvent misuse.
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Affiliation(s)
- Silvia L Cruz
- Departamento de Farmacobiología, Cinvestav, Mexico DF, Mexico.
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Pascual R, Aedo L, Meneses JC, Vergara D, Reyes A, Bustamante C. Solvent inhalation (toluene and n-hexane) during the brain growth spurt impairs the maturation of frontal, parietal and occipital cerebrocortical neurons in rats. Int J Dev Neurosci 2010; 28:491-5. [PMID: 20600790 DOI: 10.1016/j.ijdevneu.2010.06.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 05/30/2010] [Accepted: 06/14/2010] [Indexed: 11/28/2022] Open
Abstract
Solvent abuse during pregnancy may cause "fetal solvent syndrome", which is characterized by mild brain atrophy and associated with behavioral, cognitive, and emotional abnormalities. The present study investigated whether solvent inhalation during the preweaning period (P2-P21) alters the morphological maturation of frontal, parietal, and occipital cortical neurons. Twelve hours after delivery (postnatal day 0, P0), litters were cross-fostered, culled to 8 pups/dam and housed together with a dam in standard laboratory cages. Litters were randomly assigned to the "air-only" group (n=64, 8 litters) and to the "solvent-sniffer" group (n=72, 9 litters). During P2-P21, each animal was exposed daily to either organic solvent vapors (75% toluene and 18% n-hexane, a solvent mixture commonly found in glues and adhesives) or clean air. To determine the impact of early solvent inhalation on cortical neuronal differentiation, brains were stained using the Golgi-Cox-Sholl procedure to quantitatively assess neocortical pyramidal cell dendrogenesis. Preweaning, solvent-exposed animals displayed dramatic impairments in dendritic growth as well as significant reductions in brain weight and size.
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Affiliation(s)
- Rodrigo Pascual
- Escuela de Kinesiología, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
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