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Cortical astrocytes regulate ethanol consumption and intoxication in mice. Neuropsychopharmacology 2021; 46:500-508. [PMID: 32464636 PMCID: PMC8027025 DOI: 10.1038/s41386-020-0721-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 04/30/2020] [Accepted: 05/04/2020] [Indexed: 12/18/2022]
Abstract
Astrocytes are fundamental building blocks of the central nervous system. Their dysfunction has been implicated in many psychiatric disorders, including alcohol use disorder, yet our understanding of their functional role in ethanol intoxication and consumption is very limited. Astrocytes regulate behavior through multiple intracellular signaling pathways, including G-protein coupled-receptor (GPCR)-mediated calcium signals. To test the hypothesis that GPCR-induced calcium signaling is also involved in the behavioral effects of ethanol, we expressed astrocyte-specific excitatory DREADDs in the prefrontal cortex (PFC) of mice. Activating Gq-GPCR signaling in PFC astrocytes increased drinking in ethanol-naïve mice, but not in mice with a history of ethanol drinking. In contrast, reducing calcium signaling with an astrocyte-specific calcium extruder reduced ethanol intake. Cortical astrocyte calcium signaling also altered the acute stimulatory and sedative-hypnotic effects of ethanol. Astrocyte-specific Gq-DREADD activation increased both the locomotor-activating effects of low dose ethanol and the sedative-hypnotic effects of a high dose, while reduced astrocyte calcium signaling diminished sensitivity to the hypnotic effects. In addition, we found that adenosine A1 receptors were required for astrocyte calcium activation to increase ethanol sedation. These results support integral roles for PFC astrocytes in the behavioral actions of ethanol that are due, at least in part, to adenosine receptor activation.
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Palmer E, Tyacke R, Sastre M, Lingford-Hughes A, Nutt D, Ward RJ. Alcohol Hangover: Underlying Biochemical, Inflammatory and Neurochemical Mechanisms. Alcohol Alcohol 2019; 54:196-203. [PMID: 30916313 DOI: 10.1093/alcalc/agz016] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 01/31/2019] [Accepted: 02/06/2019] [Indexed: 02/06/2023] Open
Abstract
AIM To review current alcohol hangover research in animals and humans and evaluate key evidence for contributing biological factors. METHOD Narrative review with alcohol hangover defined as the state the day after a single episode of heavy drinking, when the alcohol concentration in the blood approaches zero. RESULTS Many of the human studies of hangover are not well controlled, with subjects consuming different concentrations of alcohol over variable time periods and evaluation not blinded. Also, studies have measured different symptoms and use varying methods of measurement. Animal studies show variations with respect to the route of administration (intragastric or intraperitoneal), the behavioural tests utilised and discrepancy in the timepoint used for hangover onset. Human studies have the advantage over animal models of being able to assess subjective hangover severity and its correlation with specific behaviours and/or biochemical markers. However, animal models provide valuable insight into the neural mechanisms of hangover. Despite such limitations, several hangover models have identified pathological changes which correlate with the hangover state. We review studies examining the contribution of alcohol's metabolites, neurotransmitter changes with particular reference to glutamate, neuroinflammation and ingested congeners to hangover severity. CONCLUSION Alcohol metabolites, neurotransmitter alterations, inflammatory factors and mitochondrial dysfunction are the most likely factors in hangover pathology. Future research should aim to investigate the relationship between these factors and their causal role.
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Affiliation(s)
- Emily Palmer
- Department of Medicine, Imperial College London, London, UK
| | - Robin Tyacke
- Department of Medicine, Imperial College London, London, UK
| | | | | | - David Nutt
- Department of Medicine, Imperial College London, London, UK
| | - Roberta J Ward
- Department of Medicine, Imperial College London, London, UK
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Hsieh YJ, Wu LC, Ke CC, Chang CW, Kuo JW, Huang WS, Chen FD, Yang BH, Tai HT, Chen SCJ, Liu RS. Effects of the Acute and Chronic Ethanol Intoxication on Acetate Metabolism and Kinetics in the Rat Brain. Alcohol Clin Exp Res 2017; 42:329-337. [PMID: 29205407 DOI: 10.1111/acer.13573] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 11/20/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND Ethanol (EtOH) intoxication inhibits glucose transport and decreases overall brain glucose metabolism; however, humans with long-term EtOH consumption were found to have a significant increase in [1-11 C]-acetate uptake in the brain. The relationship between the cause and effect of [1-11 C]-acetate kinetics and acute/chronic EtOH intoxication, however, is still unclear. METHODS [1-11 C]-acetate positron emission tomography (PET) with dynamic measurement of K1 and k2 rate constants was used to investigate the changes in acetate metabolism in different brain regions of rats with acute or chronic EtOH intoxication. RESULTS PET imaging demonstrated decreased [1-11 C]-acetate uptake in rat brain with acute EtOH intoxication, but this increased with chronic EtOH intoxication. Tracer uptake rate constant K1 and clearance rate constant k2 were decreased in acutely intoxicated rats. No significant change was noted in K1 and k2 in chronic EtOH intoxication, although 6 of 7 brain regions showed slightly higher k2 than baseline. These results indicate that acute EtOH intoxication accelerated acetate transport and metabolism in the rat brain, whereas chronic EtOH intoxication status showed no significant effect. CONCLUSIONS In vivo PET study confirmed the modulatory role of EtOH, administered acutely or chronically, in [1-11 C]-acetate kinetics and metabolism in the rat brain. Acute EtOH intoxication may inhibit the transport and metabolism of acetate in the brain, whereas chronic EtOH exposure may lead to the adaptation of the rat brain to EtOH in acetate utilization. [1-11 C]-acetate PET imaging is a feasible approach to study the effect of EtOH on acetate metabolism in rat brain.
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Affiliation(s)
- Ya-Ju Hsieh
- Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Liang-Chih Wu
- National PET/Cyclotron Center, Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Chien-Chih Ke
- Biomedical Imaging Research Center, National Yang-Ming University, Taipei, Taiwan.,Molecular and Genetic Imaging Core/Taiwan Mouse Clinic, National Comprehensive Mouse Phenotyping and Drug Testing Center, Taipei, Taiwan
| | - Chi-Wei Chang
- National PET/Cyclotron Center, Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Jung-Wen Kuo
- Biomedical Imaging Research Center, National Yang-Ming University, Taipei, Taiwan.,Molecular and Genetic Imaging Core/Taiwan Mouse Clinic, National Comprehensive Mouse Phenotyping and Drug Testing Center, Taipei, Taiwan
| | - Wen-Sheng Huang
- National PET/Cyclotron Center, Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Fu-Du Chen
- Biomedical Imaging Research Center, National Yang-Ming University, Taipei, Taiwan.,Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Bang-Hung Yang
- National PET/Cyclotron Center, Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.,Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Hsiao-Ting Tai
- Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Sharon Chia-Ju Chen
- Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Ren-Shyan Liu
- National PET/Cyclotron Center, Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.,Biomedical Imaging Research Center, National Yang-Ming University, Taipei, Taiwan.,Molecular and Genetic Imaging Core/Taiwan Mouse Clinic, National Comprehensive Mouse Phenotyping and Drug Testing Center, Taipei, Taiwan.,Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.,Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.,Biophotonic and Molecular Imaging Research Center, National Yang-Ming University, Taipei, Taiwan.,Department of Nuclear Medicine, Cheng-Hsin General Hospital, Taipei, Taiwan
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Possible involvement of ACSS2 gene in alcoholism. J Neural Transm (Vienna) 2017; 124:1151-1158. [PMID: 28550509 DOI: 10.1007/s00702-017-1737-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 05/20/2017] [Indexed: 02/01/2023]
Abstract
Alcoholism is a psychiatric disorder that composes one of the principal causes of health disabilities in the world population. Furthermore, the available pharmacotherapy is limited. Therefore, this research was carried out to better understand the basis of the underlying neurobiological processes of this disorder and to discover potential therapeutic targets. Real-time PCR analysis was performed in the amygdala nuclei region of the brain of mice exposed to a chronic three-bottle free-choice model (water, 5 and 10% v/v ethanol). Based on individual ethanol intake, the mice were classified into three groups: "compulsive-like" (i.e., ethanol intake not affected by quinine adulteration), "ethanol-preferring" and "ethanol non-preferring". A fourth group had access only to tap water (control group). The candidate gene ACSS2 was genotyped in human alcoholics by real-time polymerase chain reaction using the markers rs6088638 and rs7266550. Seven genes were picked out (Acss2, Acss3, Acat1, Acsl1, Acaa2, Hadh, and Hadhb) and the mRNA level of the Acss2 gene was increased only in the "compulsive-like" group (p = 0.004). The allele frequency of rs6088638 for the gene ACSS2 was higher in the Alcoholic human group (p = 0.03), although sample size was very small. The gene ACSS2 is associated with alcoholism, suggesting that biochemical pathways where it participates may have a role in the biological mechanisms susceptible to the ethanol effects.
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Pardo M, Betz AJ, San Miguel N, López-Cruz L, Salamone JD, Correa M. Acetate as an active metabolite of ethanol: studies of locomotion, loss of righting reflex, and anxiety in rodents. Front Behav Neurosci 2013; 7:81. [PMID: 23847487 PMCID: PMC3706982 DOI: 10.3389/fnbeh.2013.00081] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 06/18/2013] [Indexed: 11/15/2022] Open
Abstract
It has been postulated that a number of the central effects of ethanol are mediated via ethanol metabolites: acetaldehyde and acetate. Ethanol is known to produce a large variety of behavioral actions such anxiolysis, narcosis, and modulation of locomotion. Acetaldehyde contributes to some of those effects although the contribution of acetate is less known. In the present studies, rats and mice were used to assess the acute and chronic effects of acetate after central or peripheral administration. Male Sprague-Dawley rats were used for the comparison between central (intraventricular, ICV) and peripheral (intraperitoneal, IP) administration of acute doses of acetate on locomotion. CD1 male mice were used to study acute IP effects of acetate on locomotion, and also the effects of chronic oral consumption of acetate (0, 500, or 1000 mg/l, during 7, 15, 30, or 60 days) on ethanol- (1.0, 2.0, 4.0, or 4.5 g/kg, IP) induced locomotion, anxiolysis, and loss of righting reflex (LORR). In rats, ICV acetate (0.7–2.8 μmoles) reduced spontaneous locomotion at doses that, in the case of ethanol and acetaldehyde, had previously been shown to stimulate locomotion. Peripheral acute administration of acetate also suppressed locomotion in rats (25–100 mg/kg), but not in mice. In addition, although chronic administration of acetate during 15 days did not have an effect on spontaneous locomotion in an open field, it blocked ethanol-induced locomotion. However, ethanol-induced anxiolysis was not affected by chronic administration of acetate. Chronic consumption of acetate (up to 60 days) did not have an effect on latency to, or duration of LORR induced by ethanol, but significantly increased the number of mice that did not achieve LORR. The present work provides new evidence supporting the hypothesis that acetate should be considered a centrally-active metabolite of ethanol that contributes to some behavioral effects of this alcohol, such as motor suppression.
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Affiliation(s)
- Marta Pardo
- Àrea de Psicobiologia, Campus Riu Sec, Universitat Jaume I Castelló, Spain
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Maxwell CR, Spangenberg RJ, Hoek JB, Silberstein SD, Oshinsky ML. Acetate causes alcohol hangover headache in rats. PLoS One 2010; 5:e15963. [PMID: 21209842 PMCID: PMC3013144 DOI: 10.1371/journal.pone.0015963] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 12/01/2010] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND The mechanism of veisalgia cephalgia or hangover headache is unknown. Despite a lack of mechanistic studies, there are a number of theories positing congeners, dehydration, or the ethanol metabolite acetaldehyde as causes of hangover headache. METHODS We used a chronic headache model to examine how pure ethanol produces increased sensitivity for nociceptive behaviors in normally hydrated rats. RESULTS Ethanol initially decreased sensitivity to mechanical stimuli on the face (analgesia), followed 4 to 6 hours later by inflammatory pain. Inhibiting alcohol dehydrogenase extended the analgesia whereas inhibiting aldehyde dehydrogenase decreased analgesia. Neither treatment had nociceptive effects. Direct administration of acetate increased nociceptive behaviors suggesting that acetate, not acetaldehyde, accumulation results in hangover-like hypersensitivity in our model. Since adenosine accumulation is a result of acetate formation, we administered an adenosine antagonist that blocked hypersensitivity. DISCUSSION Our study shows that acetate contributes to hangover headache. These findings provide insight into the mechanism of hangover headache and the mechanism of headache induction.
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Affiliation(s)
- Christina R. Maxwell
- Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Rebecca Jay Spangenberg
- Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Jan B. Hoek
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Stephen D. Silberstein
- Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Michael L. Oshinsky
- Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
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8
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Abstract
Acetate, a glial-specific substrate, is an attractive alternative to glucose for the study of neuronal-glial interactions. The present study investigates the kinetics of acetate uptake and utilization in the rat brain in vivo during infusion of [2-13C]acetate using NMR spectroscopy. When plasma acetate concentration was increased, the rate of brain acetate utilization (CMR(ace)) increased progressively and reached close to saturation for plasma acetate concentration > 2-3 mM, whereas brain acetate concentration continued to increase. The Michaelis-Menten constant for brain acetate utilization (K(M)(util) = 0.01 +/- 0.14 mM) was much smaller than for acetate transport through the blood-brain barrier (BBB) (K(M)(t) = 4.18 +/- 0.83 mM). The maximum transport capacity of acetate through the BBB (V(max)(t) = 0.96 +/- 0.18 micromol/g/min) was nearly twofold higher than the maximum rate of brain acetate utilization (V(max)(util) = 0.50 +/- 0.08 micromol/g/min). We conclude that, under our experimental conditions, brain acetate utilization is saturated when plasma acetate concentrations increase above 2-3 mM. At such high plasma acetate concentration, the rate-limiting step for glial acetate metabolism is not the BBB, but occurs after entry of acetate into the brain.
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Affiliation(s)
- Dinesh K Deelchand
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
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McLaughlin PJ, Chuck TL, Arizzi-LaFrance MN, Salamone JD, Correa M. Central vs. peripheral administration of ethanol, acetaldehyde and acetate in rats: effects on lever pressing and response initiation. Pharmacol Biochem Behav 2008; 89:304-13. [PMID: 18294679 DOI: 10.1016/j.pbb.2008.01.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 01/07/2008] [Accepted: 01/09/2008] [Indexed: 11/28/2022]
Abstract
The metabolites of ethanol, acetaldehyde and acetate, are biologically active, and different effects may be produced depending upon the particular metabolite and the route of administration. These studies characterized the effects of intraperitoneal (IP) vs. intraventricular (ICV) administration of ethanol, acetaldehyde, and acetate administered to male Sprague-Dawley rats. Operant behavior was assessed by conducting a detailed temporal analysis of lever pressing with rats responding on a fixed ratio 5 schedule of food reinforcement. IP administration of all three drugs produced a rate-decreasing effect on the total number of responses. Acetaldehyde and acetate were much more potent than ethanol at reducing lever pressing. The interresponse time (IRT) distribution also was more potently altered by IP administration of ethanol metabolites than by ethanol itself. The total lever pressing and IRT distributions of ethanol- and acetaldehyde- treated rats were not significantly affected when these drugs were administered ICV, while acetate produced a marked suppression of fast responses and an increase in pausing. The metabolites of ethanol are more potent than ethanol itself in terms of altering patterns of lever pressing. Thus, the effects of ethanol administration could in part be due to the actions of its biologically active metabolites.
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Affiliation(s)
- Peter J McLaughlin
- Department of Psychology, University of Connecticut, Storrs, CT 06269-1020, USA
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10
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Tambour S, Didone V, Tirelli E, Quertemont E. Locomotor effects of ethanol and acetaldehyde after peripheral and intraventricular injections in Swiss and C57BL/6J mice. Behav Brain Res 2006; 172:145-54. [PMID: 16764949 DOI: 10.1016/j.bbr.2006.05.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 05/05/2006] [Accepted: 05/10/2006] [Indexed: 12/31/2022]
Abstract
Several studies have suggested that acetaldehyde, the first product of ethanol metabolism, is involved in the locomotor stimulant effects of ethanol in mice, although it has never been formally tested whether acetaldehyde injected directly into the brain of mice has stimulant properties. Recently, it was also shown in rats that both ethanol and acetaldehyde can induce opposite locomotor effects according to the route of administration. Whereas peripheral administrations of ethanol and acetaldehyde induced locomotor depressant effects, their infusions directly into the brain produced locomotor stimulation. The aim of the present study was to characterize in mice the locomotor effects of ethanol and acetaldehyde injected either peripherally by the intraperitoneal route or centrally into the brain ventricles. Additionally, the effects of ethanol and acetaldehyde were compared in two strains of mice known for their differential sensitivity to the locomotor effects of ethanol, namely Swiss and C57BL/6J mice. Ethanol induced a biphasic effect on locomotor activity in Swiss mice, with stimulant effects at low to moderate doses and depressant effects at higher doses. Such a profile of effects was observed whatever the route of administration, peripheral or central. In C57BL/6J mice, ethanol only induced monophasic depressant effects. In this mouse strain, no evidence of the stimulant effects of ethanol was found after either an i.p. or an i.c.v. administration of ethanol. In contrast to ethanol, acetaldehyde yielded only depressant effects in both strains of mice after both peripheral and central administrations. These results indicate that the route of administration does not alter the locomotor effects of ethanol and acetaldehyde in mice. Additionally, the present study shows that the stimulant properties of acetaldehyde, even after direct infusion into the brain, are not as obvious as previously speculated.
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Affiliation(s)
- Sophie Tambour
- Unité de Recherche en Psychologie Expérimentale et Neurosciences Cognitives (URPENC), Université de Liège, Boulevard du Rectorat 5/B32, B-4000 Liège, Belgium
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Quertemont E, Tambour S, Tirelli E. The role of acetaldehyde in the neurobehavioral effects of ethanol: A comprehensive review of animal studies. Prog Neurobiol 2005; 75:247-74. [PMID: 15882776 DOI: 10.1016/j.pneurobio.2005.03.003] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Accepted: 03/24/2005] [Indexed: 01/18/2023]
Abstract
Acetaldehyde has long been suggested to be involved in a number of ethanol's pharmacological and behavioral effects, such as its reinforcing, aversive, sedative, amnesic and stimulant properties. However, the role of acetaldehyde in ethanol's effects has been an extremely controversial topic during the past two decades. Opinions ranged from those virtually denying any role for acetaldehyde in ethanol's effects to those who claimed that alcoholism is in fact "acetaldehydism". Considering the possible key role of acetaldehyde in alcohol addiction, it is critical to clarify the respective functions of acetaldehyde and ethanol molecules in the pharmacological and behavioral effects of alcohol consumption. In the present paper, we review the animal studies reporting evidence that acetaldehyde is involved in the pharmacological and behavioral effects of ethanol. A number of studies demonstrated that acetaldehyde administration induces a range of behavioral effects. Other pharmacological studies indicated that acetaldehyde might be critically involved in several effects of ethanol consumption, including its reinforcing consequences. However, conflicting evidence has also been published. Furthermore, it remains to be shown whether pharmacologically relevant concentrations of acetaldehyde are achieved in the brain after alcohol consumption in order to induce significant effects. Finally, we review current evidence about the central mechanisms of action of acetaldehyde.
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Affiliation(s)
- Etienne Quertemont
- Laboratoire de Neurosciences Comportementales, et Psychopharmacologie, Université de Liège, Boulevard du Rectorat 5/B32, 4000 Liège, Belgium.
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Arolfo MP, Yao L, Gordon AS, Diamond I, Janak PH. Ethanol operant self-administration in rats is regulated by adenosine A2 receptors. Alcohol Clin Exp Res 2004; 28:1308-16. [PMID: 15365300 DOI: 10.1097/01.alc.0000139821.38167.20] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Recent findings suggest that adenosine is involved in the neural and behavioral effects of ethanol (EtOH). Studies in neural cell culture show that EtOH, via activation of adenosine A2 receptors, triggers cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signaling and CRE (cAMP regulatory element)-mediated gene expression and that this effect is blocked by inhibiting G-protein betagamma subunits. Recently, we reported that expression of a betagamma inhibitor in the nucleus accumbens (NAc) reduces EtOH drinking in rats. The NAc expresses high levels of the adenosine A2A receptor in GABAergic medium spiny neurons. If the reinforcing effects of EtOH are mediated through an A2 activation of cAMP/PKA signaling via betagamma, then A2 receptor blockade should attenuate EtOH consumption. Here we tested this hypothesis. Because adenosine A2 and dopamine D2 receptors are coexpressed in neurons of the NAc, we compared the effects of A2 blockade with those of D2 receptor blockade. METHODS Male Long-Evans rats were trained to self-administer 10% EtOH in daily 30-min sessions with an active and an inactive lever. Separate groups of rats were given the D2 antagonist eticlopride (0.005, 0.007, and 0.01 mg/kg), the A2 antagonist 3,7-dimethyl-1-propargylxanthine (DMPX; 1, 3, 5, 7, 10, and 20 mg/kg), and the A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.125, 0.25, and 0.5 mg/kg) by systemic injection. RESULTS Eticlopride dose-dependently reduced EtOH drinking. DMPX showed a bimodal effect: 10 and 20 mg/kg decreased, but 1 mg/kg increased, EtOH consumption. DPCPX was without effect. CONCLUSIONS In support of our hypothesis, the A2 antagonist DMPX attenuated EtOH self-administration. Low doses of the A2 antagonist enhanced EtOH drinking, consistent with the possibility that rats increase EtOH self-administration to overcome partial A2 blockade. The D2 antagonist eticlopride also decreased EtOH self-administration. These data provide the first evidence that pharmacological modulation of adenosine A2 receptors can regulate EtOH consumption in rats.
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Affiliation(s)
- Maria Pia Arolfo
- Ernest Gallo Clinic and Research Center, Department of Neurology, University of California, San Francisco, Emeryville, California 94608, USA.
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Abstract
Neuronal responses to alcohol involve several hormone- and neurotransmitter-activated signal transduction pathways. Recent studies suggest that the adenosine A2 receptor (A2) mediates important actions of alcohol. Ethanol inhibits adenosine reuptake, increases extracellular adenosine, and promotes activation of A2. This leads to enhanced cAMP/protein kinase A (PKA) signaling ranging from increases in cAMP to stimulation of cAMP-dependent cAMP response element (CRE)-mediated gene expression. Medium spiny neurons in the striatum/nucleus accumbens (NAc) express A2 and dopamine D2 receptor (D2) on the same cells. Studies in model neuronal cell lines and primary neurons in culture expressing A2 and D2 provide evidence for synergy between ethanol/A2 and D2. Subthreshold concentrations of ethanol or a D2 agonist, without effect separately, synergistically activate cAMP/PKA signaling. Thus, neurons expressing A2 and D2 on the same cells, like in the NAc, are characterized by hypersensitivity to ethanol with a simultaneous activation of dopaminergic signaling. Synergy requires adenosine and appears to be mediated by the release of free betagamma dimers from G(i/o) via D2 activation. The release of free betagamma has pathophysiological significance in the drinking animal because specific blockade of betagamma signaling in the NAc strikingly reduces voluntary alcohol consumption. These findings suggest that signaling pathways, which regulate synergy between A2 and D2, might contain molecular targets for the prevention and treatment of alcoholism and alcohol abuse.
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Affiliation(s)
- William S Mailliard
- Ernest Gallo Clinic and Research Center, University of California, San Francisco, 5858 Horton Street, Suite 200, , Emeryville, CA 94608, USA
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Correa M, Arizzi MN, Betz A, Mingote S, Salamone JD. Open field locomotor effects in rats after intraventricular injections of ethanol and the ethanol metabolites acetaldehyde and acetate. Brain Res Bull 2004; 62:197-202. [PMID: 14698353 DOI: 10.1016/j.brainresbull.2003.09.013] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The typical response to acute peripheral administration of low to high doses of ethanol in rats is a dose-dependent depression of motor activity. Nevertheless, recent studies indicate that intraventricular (ICV) injections of ethanol can produce signs of behavioral activation. In addition, considerable evidence indicates that brain metabolism of ethanol is involved in modulating some of the behavioral effects of this drug, which suggests that ethanol may have active metabolites with central actions. The present study was undertaken to investigate the effects of ICV ethanol, and its two major metabolites acetaldehyde and acetate, on open field locomotor activity in rats. Male Sprague-Dawley rats received different doses of ethanol, acetaldehyde or acetate ICV and immediately were placed in an open field chamber in which locomotion was measured. Rats injected with ICV ethanol or acetaldehyde showed an inverted U-shaped dose-response curve, with moderate doses increasing motor activity. In contrast, acetate produced a dose-dependent decrease in motor activity. These results demonstrate that central administration of low doses of ethanol can increase locomotor activity in rats, and suggest that acetaldehyde may be an active metabolite of ethanol that also can facilitate locomotor activity. Moreover, it is possible that some of the motor suppression or sedation produced by ethanol is due to the central actions of acetate.
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Affiliation(s)
- M Correa
- Department of Psychology, University of Connecticut, Storrs, CT 06269-1020, USA
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15
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Arizzi MN, Correa M, Betz AJ, Wisniecki A, Salamone JD. Behavioral effects of intraventricular injections of low doses of ethanol, acetaldehyde, and acetate in rats: studies with low and high rate operant schedules. Behav Brain Res 2003; 147:203-10. [PMID: 14659586 DOI: 10.1016/s0166-4328(03)00158-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Although ethanol is typically classed as a sedative-hypnotic, low doses of ethanol have been shown to stimulate locomotor activity in mice. However, in rats the typical response to peripheral administration of ethanol is a dose-dependent suppression of motor activity and operant responding. The present study was undertaken to determine the effects of intraventricular (ICV) infusions of ethanol, acetaldehyde, and acetate on operant performance in rats. ICV injections of ethanol, acetaldehyde, or acetate were given to rats previously trained on either a differential-reinforcement-of-low-rates-of-responding (DRL) 30-s schedule, which generates low rates of responding, or a fixed ratio 5 (FR5) schedule, which generates relatively high rates. Ethanol, acetaldehyde, and acetate all produced a rate-increasing effect in rats on the DRL 30-s schedule at moderate doses (2.8 and 1.4 micromol, respectively). Acetate also produced a rate-decreasing effect on the DRL 30-s schedule at a larger dose (8.8 micromol). Performance on the FR5 schedule was unaltered by ethanol and acetaldehyde, even at doses as high as 17.6 micromol. However, acetate produced a rate-decreasing effect on the FR5 schedule at doses of 4.4, 5.6, and 8.8 micromol. Central administration of low doses of ethanol and its metabolites can increase operant responding on some schedules in rats. Acetate is the substance that is most potent for producing rate-suppressing effects. These results indicate that the major metabolites of ethanol are pharmacologically active when injected into the brain, and suggest that acetate may mediate some of the rate-suppressing effects of ethanol, such as sedation, ataxia or motor slowing.
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Affiliation(s)
- Maria N Arizzi
- Department of Psychology, University of Connecticut, U-1020, Storrs, CT 06269-1020, USA
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16
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Eloqayli H, Dahl CB, Götestam KG, Unsgård G, Hadidi H, Sonnewald U. Pentylenetetrazole decreases metabolic glutamate turnover in rat brain. J Neurochem 2003; 85:1200-7. [PMID: 12753079 DOI: 10.1046/j.1471-4159.2003.01781.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Seizures were induced in rats by intraperitoneal injection of pentylenetetrazole (PTZ, 70 mg/kg), followed, 30 min later, by injection of [1-13C]glucose and [1,2-13C]acetate. Analyses of extracts from cortex, subcortex and cerebellum were performed using 13C magnetic resonance spectroscopy and HPLC. It could be shown that PTZ affected different brain regions differently. The total amounts of glutamate, glutamine, GABA, aspartate and taurine were decreased in the cerebellum and unchanged in the other brain regions. GABAergic neurones in the cortex and subcortex were not affected, whereas those in the cerebellum showed a pronounced decrease of GABA synthesis. However, glutamatergic neurones in all brain regions showed a decrease in glutamate labelling and in addition a decreased turnover in cerebellum. It could be shown that this decrease was in the metabolic pool of glutamate whereas release of glutamate was unaffected since glutamine labelling from glutamate was unchanged. Aspartate turnover was also decreased in all brain regions. Changes in astrocyte metabolism were not detected, indicating that PTZ had no effect on astrocyte metabolism in the early postictal stage.
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Affiliation(s)
- Haytham Eloqayli
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
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17
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Othman T, Legare D, Sadri P, Lautt WW, Parkinson FE. A preliminary investigation of the effects of maternal ethanol intake during gestation and lactation on brain adenosine A(1) receptor expression in rat offspring. Neurotoxicol Teratol 2002; 24:275-9. [PMID: 11943515 DOI: 10.1016/s0892-0362(01)00211-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Ethanol exposure during fetal development can result in behavioral and neurological deficits, including reduced cognitive functions, retarded growth, and craniofacial abnormalities. Adenosine is an endogenous neuromodulator that fine-tunes the release and/or synaptic activities of several neurotransmitters, including glutamate, dopamine, and serotonin. Our aim was to determine whether ethanol exposure during early development affects adenosine receptors, particularly the A1 receptor subtype, in adult rats. Female rats were given water or 15% (vol/vol) ethanol in water prior to mating and throughout gestation and lactation. Sixty-day-old male rat offspring from these dams were randomly selected and assayed for adenosine A1 receptor expression in four brain areas: cortex, cerebellum, hippocampus, and striatum. Our results indicate that ethanol intake by dams decreased body and brain weights of offspring and reduced both A1 receptor mRNA and protein density in cortex and cerebellum. These preliminary findings indicate that ethanol intake by dams during pregnancy and lactation can affect adenosine A1 receptor signalling in the offspring. A pair-fed controlled study is warranted to explore these findings further.
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Affiliation(s)
- Timothy Othman
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB, Canada
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18
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Parkinson FE, Zhang YW, Shepel PN, Greenway SC, Peeling J, Geiger JD. Effects of nitrobenzylthioinosine on neuronal injury, adenosine levels, and adenosine receptor activity in rat forebrain ischemia. J Neurochem 2000; 75:795-802. [PMID: 10899957 DOI: 10.1046/j.1471-4159.2000.0750795.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Adenosine levels increase in brain during cerebral ischemia, and adenosine has receptor-mediated neuroprotective effects. This study was performed to test the hypothesis that nitrobenzylthioinosine (NBMPR), a selective and potent inhibitor of one adenosine transporter subtype termed ENT1, or es, can protect against ischemic neuronal injury by enhancing adenosine levels and potentiating adenosine receptor-mediated effects, including attenuation of the cellular production and release of tumor necrosis factor-alpha (TNF-alpha). In rats, the phosphorylated prodrug form of NBMPR, NBMPR-phosphate, or saline was administered by intracerebroventricular injection 30 min before forebrain ischemia. Seven days following the ischemic episode, rats were killed, and neuronal damage in the CA1 region of the hippocampus was assessed. The number of pyramidal neurons was significantly (p < 0.001) greater in the NBMPR-P treatment group. A trend toward protection was still evident at 28 days postreperfusion. Adenosine increased significantly during ischemia to levels eight- to 85-fold above basal. NBMPR-P treatment did not cause statistically significant increases in ischemic adenosine levels; however, this treatment tended to increase adenosine levels in all brain regions at 7 min postreperfusion. Ischemia-induced expression of TNF-alpha was not altered by NBMPR-P treatment, and the nonselective adenosine receptor antagonist 8-(p-sulfophenyl) theophylline did not abolish the neuroprotective effects of NBMPR-P treatment. These data indicate that NBMPR can protect CA1 pyramidal neurons from ischemic death without statistically significant effects on adenosine levels or adenosine receptor-mediated inhibition of the proinflammatory cytokine TNF-alpha.
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Affiliation(s)
- F E Parkinson
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Canada.
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19
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Håberg A, Qu H, Haraldseth O, Unsgård G, Sonnewald U. In vivo effects of adenosine A1 receptor agonist and antagonist on neuronal and astrocytic intermediary metabolism studied with ex vivo 13C NMR spectroscopy. J Neurochem 2000; 74:327-33. [PMID: 10617136 DOI: 10.1046/j.1471-4159.2000.0740327.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Adenosine is a neuromodulator, and it has been suggested that cerebral acetate metabolism induces adenosine formation. In the present study the effects that acetate has on cerebral intermediary metabolism, compared with those of glucose, were studied using the adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA) and antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Fasted rats received an intravenous injection of CCPA, DPCPX, or vehicle. Fifteen minutes later either [1,2-13C]acetate or [1-13C]glucose was given intraperitoneally; after another 30 min the rats were decapitated. Cortical extracts were analyzed with 13C NMR spectroscopy and HPLC analysis. DPCPX affected neuronal and astrocytic metabolism. De novo synthesis of GABA from neuronal and astrocytic precursors was significantly reduced. De novo syntheses of glutamate and aspartate were at control levels, but their degradation was significantly elevated. In glutamine the anaplerotic activity and the amount of label in the position representing the second turn in the tricarboxylic acid cycle were significantly increased, suggesting elevated metabolic activity in astrocytes. CCPA did not influence GABA, aspartate, or glutamine synthesis. In glutamate the contribution from the astrocytic anaplerotic pathway was significantly decreased. In the present study the findings in the [1,2-13C]acetate and [1-13C]glucose control, CCPA, and DPCPX groups were complementary, and no adenosine A1 agonist effects arising from cerebral acetate metabolism were detected.
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Affiliation(s)
- A Håberg
- Department of Anesthesia and Medical Imaging, Trondheim University Hospital, Norway
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20
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Chau A, Koos BJ. Metabolic and cardiorespiratory responses to hypoxia in fetal sheep: adenosine receptor blockade. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:R1805-11. [PMID: 10362763 DOI: 10.1152/ajpregu.1999.276.6.r1805] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
8-Phenyltheophylline (PT), a potent and specific inhibitor of adenosine receptors, was infused intra-arterially into unanesthetized fetal sheep to determine the role of adenosine in hypoxic inhibition of fetal breathing. PT in normoxic fetuses increased heart rate and the incidence of low-voltage electrocortical activity, rapid eye movements (REM), and breathing. Mean breath amplitude increased by 44%. Hypoxia (preductal arterial PO2 = 14 Torr) induced a metabolic acidemia, a transient bradycardia, and hypertension while virtually eliminating REM and breathing. PT administration during hypoxia enhanced the metabolic acidemia, blocked the bradycardia and hypertension, increased the incidence of REM and breathing, and elevated mean breath amplitude. The results indicate that 1) adenosine is involved in fetal glycolytic and cardiovascular responses to hypoxia, 2) activation of central adenosine receptors mediates about one-half the inhibitory effects of hypoxia on REM and breathing, and 3) the depression of breathing may critically depend on a hypoxia-induced reduction in phasic REM sleep.
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Affiliation(s)
- A Chau
- Department of Obstetrics and Gynecology, Nicholas S. Assali Perinatal Research Laboratory, School of Medicine, The Brain Research Institute, University of California, Los Angeles, California 90095-1740, USA
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