1
|
Overview of the Neuroprotective Effects of the MAO-Inhibiting Antidepressant Phenelzine. Cell Mol Neurobiol 2021; 42:225-242. [PMID: 33839994 PMCID: PMC8732914 DOI: 10.1007/s10571-021-01078-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 03/10/2021] [Indexed: 12/18/2022]
Abstract
Phenelzine (PLZ) is a monoamine oxidase (MAO)-inhibiting antidepressant with anxiolytic properties. This multifaceted drug has a number of pharmacological and neurochemical effects in addition to inhibition of MAO, and findings on these effects have contributed to a body of evidence indicating that PLZ also has neuroprotective/neurorescue properties. These attributes are reviewed in this paper and include catabolism to the active metabolite β-phenylethylidenehydrazine (PEH) and effects of PLZ and PEH on the GABA-glutamate balance in brain, sequestration of reactive aldehydes, and inhibition of primary amine oxidase. Also discussed are the encouraging findings of the effects of PLZ in animal models of stroke, spinal cord injury, traumatic brain injury, and multiple sclerosis, as well other actions such as reduction of nitrative stress, reduction of the effects of a toxin on dopaminergic neurons, potential anticonvulsant actions, and effects on brain-derived neurotrophic factor, neural cell adhesion molecules, an anti-apoptotic factor, and brain levels of ornithine and N-acetylamino acids.
Collapse
|
2
|
Transgenic overexpression of furin increases epileptic susceptibility. Cell Death Dis 2018; 9:1058. [PMID: 30333479 PMCID: PMC6193048 DOI: 10.1038/s41419-018-1076-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 09/01/2018] [Accepted: 09/07/2018] [Indexed: 11/28/2022]
Abstract
The proprotein convertase Furin plays crucial roles in the pathology of many diseases. However, the specific role of furin in epilepsy remains unclear. In our study, furin protein was increased in the temporal neocortex of epileptic patients and in the hippocampus and cortex of epileptic mice. The furin transgenic (TG) mice showed increased susceptibility to epilepsy and heightened epileptic activity compared with wild-type (WT) mice. Conversely, lentivirus-mediated knockdown of furin restrained epileptic activity. Using whole-cell patch clamp, furin knockdown and overexpression influenced neuronal inhibitory by regulating postsynaptic gamma-aminobutyric acid A receptor (GABAAR)-mediated synaptic transmission. Importantly, furin influenced the expression of GABAAR β2/3 membrane and total protein in epileptic mice by changing transcription level of GABAAR β2/3, not the protein degradation. These results reveal that furin may regulate GABAAR-mediated inhibitory synaptic transmission by altering the transcription of GABAAR β2/3 subunits in epilepsy; this finding could provide new insight into epilepsy prevention and treatment.
Collapse
|
3
|
Can NÖ, Osmaniye D, Levent S, Sağlık BN, İnci B, Ilgın S, Özkay Y, Kaplancıklı ZA. Synthesis of New Hydrazone Derivatives for MAO Enzymes Inhibitory Activity. Molecules 2017; 22:molecules22081381. [PMID: 28825649 PMCID: PMC6152084 DOI: 10.3390/molecules22081381] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 08/02/2017] [Accepted: 08/15/2017] [Indexed: 01/18/2023] Open
Abstract
In the present work, 14 new 1-substituted-2-phenylhydrazone derivatives were synthesized to evaluate their inhibitory activity against hMAO enzymes. The structures of the newly synthesized hydrazones 2a–2n were characterized by IR, 1H-NMR, 13C-NMR, HR-MS spectroscopic methods. The inhibitory activity of compounds 2a–2n against hMAO-A and hMAO-B enzymes was elucidated by using an in-vitro Amplex Red® reagent assay based on fluorometric methods. According to the activity studies, 2a and 2b were found to be the most active compounds against hMAO-A enzyme, with IC50 values of 0.342 µM and 0.028 µM, respectively. The most active compounds 2a–2b were evaluated by means of enzyme kinetics and docking studies. Moreover, these compounds were subjected to cytotoxicity and genotoxicity tests to establish their preliminary toxicological profiles and were found to be non-cytotoxic and non-genotoxic. Consequently, the findings of this study display the biological importance of compounds 2a, 2b as selective, irreversible and competitive inhibitors of hMAO-A. Docking studies revealed that there is a strong interaction between hMAO-A and the most active compound 2b.
Collapse
Affiliation(s)
- Nafiz Öncü Can
- Department of Analytical Chemistry, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
- Doping and Narcotic Compounds Analysis Laboratory, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Derya Osmaniye
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
- Doping and Narcotic Compounds Analysis Laboratory, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Serkan Levent
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
- Doping and Narcotic Compounds Analysis Laboratory, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Begüm Nurpelin Sağlık
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
- Doping and Narcotic Compounds Analysis Laboratory, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Beril İnci
- Department of Pharmaceutical Toxicology, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Sinem Ilgın
- Department of Pharmaceutical Toxicology, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Yusuf Özkay
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
- Doping and Narcotic Compounds Analysis Laboratory, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| | - Zafer Asım Kaplancıklı
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Anadolu Universty, 26470 Eskişehir, Turkey.
| |
Collapse
|
4
|
Li X, Zhang HJ, Wang Q, Zhang DW, Wu D, Li W, Quan ZS. Current Study of the Mechanism of Action of the Potential Anti-Epileptic Agent Q808. Molecules 2017; 22:molecules22071134. [PMID: 28686214 PMCID: PMC6152255 DOI: 10.3390/molecules22071134] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 07/01/2017] [Indexed: 11/23/2022] Open
Abstract
Our previous study showed that the anticonvulsant Q808 might be effective against seizures induced by maximal electroshock, pentylenetetrazole (PTZ), isoniazid (ISO), thiosemicarbazide (THIO), and 3-mercaptopropionic acid (3-MP). In the present study, we explored the possible mechanism of action of Q808. Results obtained with high-performance liquid chromatography (HPLC) suggest that Q808 may affect neurotransmitter content in the brain, by specifically increasing GABA content in the rat hippocampus at doses of 40 mg/kg and 80 mg/kg, and by reducing the content of glutamate and glutamine in the rat thalamus at a dose of 80 mg/kg. Intriguingly, there were no changes in the neurotransmitter content in the cortex in response to Q808. In vitro brain slice electrophysiological studies showed that 10−5 M Q808 enhanced the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in corn cells of the CA1 area of the hippocampus, and had no effect on the amplitude of sIPSCs, the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs), or γ-aminobutyric acid (GABA) receptor-mediated currents in primary cultured hippocampal neurons. These findings suggest that the antiepileptic activity of Q808 may be due to its ability to increase the amount of GABA between synapses, without affecting the function of GABA receptors.
Collapse
Affiliation(s)
- Xiang Li
- Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, College of Life Sciences, Jilin University, No. 2699 Qianjin Street, Changchun 130012, China.
| | - Hong-Jian Zhang
- Key Laboratory of Natural Resources and Functional Molecules of the Changbai Mountain, Affiliated Ministry of Education, College of Pharmacy, Yanbian University, Yanji 133002, China.
| | - Qing Wang
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Dian-Wen Zhang
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Di Wu
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Wei Li
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Zhe-Shan Quan
- Key Laboratory of Natural Resources and Functional Molecules of the Changbai Mountain, Affiliated Ministry of Education, College of Pharmacy, Yanbian University, Yanji 133002, China.
| |
Collapse
|
5
|
MacKenzie EM, Song MS, Dursun SM, Tomlinson S, Todd KG, Baker GB. Phenelzine: An Old Drug That May Hold Clues to The Development of New Neuroprotective Agents. ACTA ACUST UNITED AC 2016. [DOI: 10.1080/10177833.2010.11790656] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Erin M. MacKenzie
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Mee-Sook Song
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Serdar M. Dursun
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Sara Tomlinson
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Kathryn G. Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Glen B. Baker
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| |
Collapse
|
6
|
Saghazadeh A, Mahmoudi M, Meysamie A, Gharedaghi M, Zamponi GW, Rezaei N. Possible role of trace elements in epilepsy and febrile seizures: a meta-analysis. Nutr Rev 2015; 73:760-79. [DOI: 10.1093/nutrit/nuv026] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
|
7
|
Schipper S, Aalbers MW, Rijkers K, Swijsen A, Rigo JM, Hoogland G, Vles JSH. Tonic GABAA Receptors as Potential Target for the Treatment of Temporal Lobe Epilepsy. Mol Neurobiol 2015; 53:5252-65. [PMID: 26409480 PMCID: PMC5012145 DOI: 10.1007/s12035-015-9423-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 09/03/2015] [Indexed: 12/11/2022]
Abstract
Tonic GABAA receptors are a subpopulation of receptors that generate long-lasting inhibition and thereby control network excitability. In recent years, these receptors have been implicated in various neurological and psychiatric disorders, including Parkinson’s disease, schizophrenia, and epilepsy. Their distinct subunit composition and function, compared to phasic GABAA receptors, opens the possibility to specifically modulate network properties. In this review, the role of tonic GABAA receptors in epilepsy and as potential antiepileptic target will be discussed.
Collapse
Affiliation(s)
- S Schipper
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands.
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands.
| | - M W Aalbers
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
| | - K Rijkers
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Neurosurgery and Orthopedic Surgery, Atrium Hospital Heerlen, Heerlen, The Netherlands
| | - A Swijsen
- BIOMED Research Institute, Hasselt University/Transnational University Limburg, Martelarenlaan 42, 3500, Hasselt, Belgium
| | - J M Rigo
- BIOMED Research Institute, Hasselt University/Transnational University Limburg, Martelarenlaan 42, 3500, Hasselt, Belgium
| | - G Hoogland
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Neurosurgery, Maastricht University Medical Center, Maastricht, The Netherlands
| | - J S H Vles
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
| |
Collapse
|
8
|
Song MS, Matveychuk D, MacKenzie EM, Duchcherer M, Mousseau DD, Baker GB. An update on amine oxidase inhibitors: multifaceted drugs. Prog Neuropsychopharmacol Biol Psychiatry 2013; 44:118-24. [PMID: 23410524 DOI: 10.1016/j.pnpbp.2013.02.001] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Revised: 01/31/2013] [Accepted: 02/03/2013] [Indexed: 02/08/2023]
Abstract
Although not used as extensively as other antidepressants for the treatment of depression, the monoamine oxidase (MAO) inhibitors continue to hold a niche in psychiatry and to have a relatively broad spectrum with regard to treatment of psychiatric and neurological disorders. Experimental and clinical research on MAO inhibitors has been expanding in the past few years, primarily because of exciting findings indicating that these drugs have neuroprotective properties (often independently of their ability to inhibit MAO). The non-selective and irreversible MAO inhibitors tranylcypromine (TCP) and phenelzine (PLZ) have demonstrated neuroprotective properties in numerous studies targeting elements of apoptotic cascades and neurogenesis. l-Deprenyl and rasagiline, both selective MAO-B inhibitors, are used in the management of Parkinson's disease, but these drugs may be useful in the treatment of other neurodegenerative disorders given that they demonstrate neuroprotective/neurorescue properties in a wide variety of models in vitro and in vivo. Although the focus of studies on the involvement of MAO inhibitors in neuroprotection has been on MAO-B inhibitors, there is a growing body of evidence demonstrating that MAO-A inhibitors may also have neuroprotective properties. In addition to MAO inhibition, PLZ also inhibits primary amine oxidase (PrAO), an enzyme implicated in the etiology of Alzheimer's disease, diabetes and cardiovascular disease. These multifaceted aspects of amine oxidase inhibitors and some of their metabolites are reviewed herein.
Collapse
Affiliation(s)
- Mee-Sook Song
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, Canada
| | | | | | | | | | | |
Collapse
|
9
|
Matveychuk D, Nunes E, Ullah N, Velázquez-Martinez CA, MacKenzie EM, Baker GB. Comparison of phenelzine and geometric isomers of its active metabolite, β-phenylethylidenehydrazine, on rat brain levels of amino acids, biogenic amine neurotransmitters and methylamine. J Neural Transm (Vienna) 2013; 120:987-96. [PMID: 23392617 DOI: 10.1007/s00702-013-0978-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 01/10/2013] [Indexed: 01/27/2023]
Abstract
Phenelzine is a monoamine oxidase (MAO) inhibitor used in treatment of depression and anxiety disorders. It also elevates brain levels of γ-aminobutyric acid (GABA) and inhibits primary amine oxidase (PrAO), an enzyme whose activity and/or expression has been reported to be increased in diabetes mellitus, Alzheimer's disease and cardiovascular disorders. Phenelzine is not only an inhibitor of, but also a substrate for, MAO and it has been suggested that an active metabolite, namely β-phenylethylidenehydrazine (PEH), is responsible for phenelzine's effects on amino acids. PEH is also a strong inhibitor of PrAO but has weak effects on MAO. PEH has a double bond and can thus exist as (E)- and (Z)-geometric isomers, but to date the two isomers have not been compared with regard to their neurochemical effects. We have investigated the effects of phenelzine, (E)- and (Z)-PEH on rat whole brain levels of amino acids, biogenic amine neurotransmitters and methylamine (an endogenous substrate of PrAO). Under the conditions used in the study, (E)- and (Z)-PEH appear to be equivalent in their neurochemical properties. Both PEH isomers and phenelzine produced marked increases in rat brain levels of GABA and alanine while decreasing brain levels of glutamine. Phenelzine increased brain levels of biogenic amine neurotransmitters (noradrenaline, dopamine and serotonin), whereas neither PEH isomer altered levels of these neurotransmitters to a considerable extent. All three drugs significantly increased rat brain levels of methylamine, with (E)- and (Z)-PEH causing a greater increase than phenelzine. These results are discussed in relation to the possible therapeutic applications of these drugs.
Collapse
Affiliation(s)
- Dmitriy Matveychuk
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.
| | | | | | | | | | | |
Collapse
|
10
|
He S, Wang Q, He J, Pu H, Yang W, Ji J. Proteomic analysis and comparison of the biopsy and autopsy specimen of human brain temporal lobe. Proteomics 2006; 6:4987-96. [PMID: 16912969 DOI: 10.1002/pmic.200600078] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The proteomic study on human temporal lobe can help us to understand the physiological function of CNS in normal as well as in pathological state. Proteomic tools are potent for the assessment of protein stability post mortem. In this pilot study, the human temporal lobe biopsy specimen with chronic pharmacoresistant temporal lobe epilepsy (TLE) and autopsy specimen in control were separated by 2-DE. Using MALDI-TOF-MS and MS/MS, 375 protein spots were identified which were the products of 267 genes. Six down-regulated and 23 up-regulated protein spots in the autopsy specimen were ascertained after the gel image analysis with the ImageMaster software. A number of proteins that include neurotransmitter metabolic and glycolytic enzymes, cytoprotective proteins and cytoskeleton were found decreased while the precursor of apolipoprotein A-I increased in the TLE brain. We tried several methods to prepare the protein samples and found that DNase and RNase treatment, ultracentrifugation and Amersham clean-up kit purification can improve gel separation quality. This work optimized the sample preparation method and constructed a primary protein database of human temporal lobe and found some proteins with remarkable level change probably involved in the post-mortem process and chronic pharmacoresistant TLE pathogenesis.
Collapse
Affiliation(s)
- Sizhi He
- Department of Biochemistry and Molecular Biology, College of Life Sciences, National Laboratory of Protein Engineering and Plant Genetic Engineering, Peking University, Beijing, PR China
| | | | | | | | | | | |
Collapse
|
11
|
Quilichini PP, Chiron C, Ben-Ari Y, Gozlan H. Stiripentol, a Putative Antiepileptic Drug, Enhances the Duration of Opening of GABAA-Receptor Channels. Epilepsia 2006; 47:704-16. [PMID: 16650136 DOI: 10.1111/j.1528-1167.2006.00497.x] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Stiripentol (STP) is currently an efficient drug for add-on therapy in infantile epilepsies because it improves the efficacy of antiepileptic drugs (AEDs) through its potent inhibition of liver cytochromes P450. In addition, STP directly reduces seizures in several animal models of epilepsy, suggesting that it might also have anticonvulsive effects of its own. However, its underlying mechanisms of action are unknown. METHODS We examined the interactions of STP with gamma-aminobutyric acid (GABA) transmission by using patch-clamp methods in CA3 pyramidal neurons in the neonatal rat. RESULTS STP markedly increased miniature inhibitory postsynaptic current (mIPSC) decay-time constant in a concentration-dependent manner. The prolongation of mIPSC duration does not result from an interaction with GABA transporters because it persisted in the presence of GAT-1 inhibitors (SKF-89976A and NO-711). An interaction with benzodiazepine or neurosteroid binding sites also was excluded because STP-mediated increase of decay time was still observed when these sites were initially saturated (by clobazam, zolpidem, or pregnanolone) or blocked (by flumazenil or dehydroepiandrosterone sulfate), respectively. In contrast, saturating barbiturate sites with pentobarbital clearly occluded this effect of STP, suggesting that STP and barbiturates interact at the same locus. This was directly confirmed by using outside-out patches, because STP increased the duration and not the frequency of opening of GABAA channels. CONCLUSIONS At clinically relevant concentrations, STP enhances central GABA transmission through a barbiturate-like effect, suggesting that STP should possess an antiepileptic effect by itself.
Collapse
|
12
|
Yang J, Shen J. In vivo evidence for reduced cortical glutamate-glutamine cycling in rats treated with the antidepressant/antipanic drug phenelzine. Neuroscience 2005; 135:927-37. [PMID: 16154287 DOI: 10.1016/j.neuroscience.2005.06.067] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Revised: 06/23/2005] [Accepted: 06/27/2005] [Indexed: 10/25/2022]
Abstract
Converging evidence has indicated that hyperglutamatergic activity and GABAergic dysfunction may play important roles in the neurobiology and treatment of depression and other mood disorders. In this study, in vivo 1H[13C] magnetic resonance spectroscopy was used to quantify the effects of acute phenelzine administration on cortical energetics, glutamate neurotransmission, and GABA synthesis flux. The time-resolved kinetics of cortical [4-13C]glutamate, [4-13C]glutamine, and [2-13C]GABA turnover from i.v.-infused [1,6-13C2]glucose was measured at 11.7 T in alpha-chloralose anesthetized rats four hours after phenelzine treatment (10 mg/kg, i.p.) and in non-treated controls. The rate of the tricarboxylic acid cycle flux was not affected by phenelzine treatment compared with the non-treated group (0.46+/-0.05 vs. 0.50+/-0.05 micromol/g/min, respectively). The rate of the glutamate-glutamine cycling flux between neurons and glia in the phenelzine-treated group was significantly reduced (from 0.16+/-0.04 to 0.10+/-0.03 micromol/g/min), providing in vivo evidence that phenelzine attenuates glutamate neurotransmission. Following phenelzine treatment, the cortical GABA concentration increased significantly (from 1.02+/-0.17 to 2.30+/-0.26 micromol/g), while the GABA synthesis flux was unchanged (from 0.07+/-0.02 to 0.06+/-0.02 micromol/g/min). The possible role of augmented GABAergic function resulting from elevated GABA levels in the observed modulatory effect of phenelzine on the glutamate-glutamine cycling flux was discussed. The reduced glutamate-glutamine cycling flux observed in this study suggests that, in addition to its effects on monoaminergic and GABAergic systems, the attenuation of glutamate neurotransmission resulting from phenelzine administration may also contribute to its efficacy in the treatment of depression. This study is the first demonstration that the glutamate-glutamine cycling flux, which can be measured non-invasively in the human brain in vivo, was altered due to the action of a psychotropic drug.
Collapse
Affiliation(s)
- J Yang
- Molecular Imaging Branch, Mood and Anxiety Disorders Program, National Institute of Mental Health, Building 10, Room 2D51A, 9000 Rockville Pike, Bethesda, MD 20892-1527, USA
| | | |
Collapse
|