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Yu J, Wang DS, Bonin RP, Penna A, Alavian-Ghavanini A, Zurek AA, Rauw G, Baker GB, Orser BA. Gabapentin increases expression of δ subunit-containing GABA A receptors. EBioMedicine 2019; 42:203-213. [PMID: 30878595 PMCID: PMC6491385 DOI: 10.1016/j.ebiom.2019.03.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 02/22/2019] [Accepted: 03/04/2019] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Gabapentin is a structural analog of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Its anticonvulsant, analgesic and anxiolytic properties suggest that it increases GABAergic inhibition; however, the molecular basis for these effects is unknown as gabapentin does not directly modify GABA type A (GABAA) receptor function, nor does it modify synaptic inhibition. Here, we postulated that gabapentin increases expression of δ subunit-containing GABAA (δGABAA) receptors that generate a tonic inhibitory conductance in multiple brain regions including the cerebellum and hippocampus. METHODS Cell-surface biotinylation, Western blotting, electrophysiologic recordings, behavioral assays, high-performance liquid chromatography and gas chromatography-mass spectrometry studies were performed using mouse models. FINDINGS Gabapentin enhanced expression of δGABAA receptors and increased a tonic inhibitory conductance in neurons. This increased expression likely contributes to GABAergic effects as gabapentin caused ataxia and anxiolysis in wild-type mice but not δ subunit null-mutant mice. In contrast, the antinociceptive properties of gabapentin were observed in both genotypes. Levels of GABAA receptor agonists and neurosteroids in the brain were not altered by gabapentin. INTERPRETATION These results provide compelling evidence to account for the GABAergic properties of gabapentin. Since reduced expression of δGABAA receptor occurs in several disorders, gabapentin may have much broader therapeutic applications than is currently recognized. FUND: Supported by a Foundation Grant (FDN-154312) from the Canadian Institutes of Health Research (to B.A.O.); a NSERC Discovery Grant (RGPIN-2016-05538), a Canada Research Chair in Sensory Plasticity and Reconsolidation, and funding from the University of Toronto Centre for the Study of Pain (to R.P.B.).
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Affiliation(s)
- Jieying Yu
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Dian-Shi Wang
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Robert P Bonin
- Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON M5S 3M2, Canada
| | - Antonello Penna
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Anesthesia and Centro de Investigación Clínica Avanzada, Universidad de Chile, Santiago, 838 0456, Chile
| | | | - Agnieszka A Zurek
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Gail Rauw
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2G3, Canada
| | - Glen B Baker
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2G3, Canada
| | - Beverley A Orser
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Anesthesia, University of Toronto, Toronto, ON M5G 1E2, Canada; Department of Anesthesia, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada.
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Xu H, Wang W, Tang ZQ, Xu TL, Chen L. Taurine acts as a glycine receptor agonist in slices of rat inferior colliculus. Hear Res 2006; 220:95-105. [PMID: 16949227 DOI: 10.1016/j.heares.2006.07.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 07/13/2006] [Accepted: 07/17/2006] [Indexed: 11/18/2022]
Abstract
Taurine is an important endogenous amino acid for neural development and for many physiological functions, but little is known about its functional role in the central auditory system. We investigated in young rats (P10-P14) the effects of taurine on the neuronal responses and synaptic transmissions in the central nucleus of the inferior colliculus (ICC) with a brain slice preparation and with whole-cell patch-clamp recordings. Perfusion of taurine at 1mM reliably evoked a current across the membrane and decreased the input resistance in neurons of the ICC. Taurine also depressed the spontaneous and current-evoked firing of ICC neurons. All these effects were reversible after washout and could be blocked by 3 microM strychnine, an antagonist of glycine receptors, but not by 10 microM bicuculline, an antagonist of GABA(A) receptors. When the inhibitory receptors were not pharmacologically blocked, taurine reversibly reduced the postsynaptic currents/potentials evoked by electrically stimulating the commissure of the inferior colliculus or the ipsilateral lateral lemniscus. The results demonstrate that taurine reduces the neuronal excitability and depresses the synaptic transmission in the ICC by activating glycine-gated chloride channels. Our findings suggest that taurine acts as a ligand of glycine receptors in the ICC and can be involved in the information processing of the central auditory system similarly like the neurotransmitter glycine.
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Affiliation(s)
- Han Xu
- Auditory Research Laboratory, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
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Xu H, Zhou KQ, Huang YN, Chen L, Xu TL. Taurine activates strychnine-sensitive glycine receptors in neurons of the rat inferior colliculus. Brain Res 2004; 1021:232-40. [PMID: 15342271 DOI: 10.1016/j.brainres.2004.07.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2004] [Indexed: 11/20/2022]
Abstract
Taurine (Tau) is one of the most abundant free amino acids in the mammalian central nervous system. Whether the neurotransmission of the central auditory system is regulated or modulated by Tau is not clear. In the present study, we investigated the electrophysiological and pharmacological properties of Tau-activated currents in acutely dissociated neurons of the rat inferior colliculus (IC) using whole cell patch clamp recordings. At a holding potential of -60 mV and under a condition of chloride equilibrium potential near 0 mV, Tau activated an inward current and its half-maximal activation concentration was equal to 0.37 mM. The measured reversal potential of Tau-activated currents was close to theoretical chloride equilibrium potential. The currents evoked by Tau at both low (1 mM) and high (10 mM) concentrations were almost completely inhibited by strychnine, a glycine receptor antagonist. The Tau-activated current, however, was not affected by bicuculline, a GABA(A) receptor antagonist. Tau at increased concentrations progressively reduced the current response to subsequent glycine application. At saturated concentrations, Tau-activated current and glycine-activated current were mutually cross-desensitized by each other. These findings indicate that Tau activates glycine receptors in neurons of the rat IC and thus may have a functional role in regulating or modulating the neurotransmission of the central auditory system in mammals.
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Affiliation(s)
- Han Xu
- Department of Neurobiology and Biophysics, School of Life Sciences, University of Science and Technology of China, PO Box 4, Hefei 230027, China
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Abstract
The synaptic mechanisms underlying excitation in the rat's central nucleus of the inferior colliculus (ICC) were examined by making whole-cell patch clamp recordings in brain slice preparations of the auditory midbrain. Responses were elicited by current pulse stimulation of the lateral lemniscus and recordings were made in ICC using either current clamp or voltage clamp methods. The excitatory postsynaptic responses in either current or voltage clamp mode consisted of two distinct components, an early component that could be blocked by bath application of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) or 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), and a later component that could be blocked by application of the N-methyl-D-aspartate (NMDA) receptor antagonists, (+/-)-2-amino-5-phosphonovaleric acid (APV) or (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP). Both AMPA and NMDA receptor-mediated responses were present at resting potential and could be isolated pharmacologically by application of receptor antagonists. Voltage clamp experiments revealed that the NMDA receptor-mediated current was voltage-dependent and increased in magnitude as the cell membrane was depolarized. This NMDA receptor-mediated response was enhanced at resting potential when Mg(2+) was eliminated from the bath solution. The ratio of response amplitudes associated with the late and early components, an estimate of the relative contribution of NMDA and AMPA receptor types, changed with age. There was a progressive decline in the ratio between 9 and 13 days of age, but no further reduction between days 13 and 16. The data show that both AMPA and NMDA receptors are important for determining excitatory responses in the ICC and that both receptor types probably play a role in auditory processing after the onset of hearing.
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Affiliation(s)
- Chun Lei Ma
- Laboratory of Sensory Neuroscience, 335 Life Sciences Research Building, Institute of Neuroscience, Carleton University, 1125 Colonel By Drive, K1S 5B6, Ottawa, ON, Canada
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Yasuda S, Ishida N, Higashiyama A, Morinobu S, Kato N. Characterization of audiogenic-like seizures in naive rats evoked by activation of AMPA and NMDA receptors in the inferior colliculus. Exp Neurol 2000; 164:396-406. [PMID: 10915578 DOI: 10.1006/exnr.2000.7401] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of glutamate receptors in the inferior colliculus (IC) in audiogenic and audiogenic-like seizures was investigated in adult rats with transient neonatal hypothyroidism by 0.02% propylthiouracil (PTU) treatment through mother's milk (PTU rats) and in naive rats treated intracisternally with N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid (AMPA), or cyclothiazide, an inhibitor of rapid AMPA receptor desensitization. All rats showed audiogenic or audiogenic-like seizures characterized by running fit (RF) and generalized tonic-clonic seizures (GTCS). While systemically administered MK-801 inhibited GTCS, intracisternally administered NBQX inhibited RF and GTCS in both audiogenic and audiogenic-like seizures. Auditory stimulation shortened the latency to GTCS induced by AMPA, but not NMDA, at a subclinical dose and further elongated the shortened duration of RF, but not GTCS, induced by MK-801 pretreatment. Furthermore, Northern blot analysis was used to evaluate the expression of the immediate-early gene c-fos in the IC following induction of audiogenic or audiogenic-like seizures. The significant induction of c-fos mRNA by audiogenic seizures in PTU rats or by AMPA- or cyclothiazide-induced seizures in naive rats was prominent in the IC. MK-801 suppressed c-fos mRNA expression in the IC induced by audiogenic seizures in PTU rats or by AMPA-induced seizures in naive rats. NBQX suppressed the expression of c-fos mRNA in the IC induced by AMPA-induced seizures but did not suppress c-fos mRNA in PTU rats or rats with cyclothiazide-induced seizures. Auditory stimuli failed to affect c-fos mRNA induction by AMPA. The present study suggests that audiogenic-like seizures can be reproduced by glutamate receptor agonists in which AMPA receptors are primarily linked to the initiation of audiogenic seizures (RF) while NMDA receptors presumably located within the IC are involved in the propagation of GTCS in audiogenic seizures.
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Affiliation(s)
- S Yasuda
- Department of Psychiatry, Shiga University of Medical Science, Setatsukinowa-cho, Otsu, 520-2192, Japan
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Ross CD, Godfrey DA, Parli JA. Amino acid concentrations and selected enzyme activities in rat auditory, olfactory, and visual systems. Neurochem Res 1995; 20:1483-90. [PMID: 8789612 DOI: 10.1007/bf00970598] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Homogenates of specific brain regions of three sensory systems (auditory, olfactory, and visual) were prepared from pigmented Long-Evans Hooded rats and assayed for amino acid concentrations and activities of glutaminase, aspartate aminotransferase (total, cytosolic, and by difference, mitochondrial), malate dehydrogenase, lactate dehydrogenase, and choline acetyltransferase. Comparing the quantitative distributions among regions revealed significant correlations between AAT and aspartate, between glutaminase and glutamate, between glutamate and glutamine, and between AAT plus glutaminase, or glutaminase alone, and the sum of aspartate, glutamate, and GABA, suggesting a metabolic pathway involving the synthesis of a glutamate pool as precursor to aspartate and GABA. Of the inhibitory transmitter amino acids, GABA concentrations routinely exceeded those of glycine, but glycine concentrations were relatively high in brainstem auditory structures.
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Affiliation(s)
- C D Ross
- Department of Otorhinolaryngology, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA
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Ferraro TN, Golden GT, Smith GG, Berrettini WH. Differential susceptibility to seizures induced by systemic kainic acid treatment in mature DBA/2J and C57BL/6J mice. Epilepsia 1995; 36:301-7. [PMID: 7614915 DOI: 10.1111/j.1528-1157.1995.tb00999.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Mature DBA/2J (D2) and C57BL/6J (B6) mice aged 9-10 weeks were studied to determine susceptibility to behavioral seizures induced by kainic acid (KA) and the possible influence exerted by differences in metabolism and blood-brain barrier (BBB) transport. Mice were observed for 4 h after subcutaneous (s.c.) KA injection. Behavioral seizure parameters included latency to first seizure (clonus), latency to tonic/clonic seizure, and latency to status epilepticus (SE). At a KA dose of 25 mg/kg, 80% of D2 mice exhibited tonic/clonic seizures, whereas all B6 mice remained seizure-free. At 30 mg/kg, tonic/clonic seizures were observed in 100% of D2 mice and 25% of B6 mice. Of D2 mice exhibiting at least one clonic seizure in response to KA at a dose of 25 mg/kg, 50% entered SE and eventually died. Administration of [3H]KA (6.6 x 10(6) dpm) at doses of 25 mg/kg (convulsive) or 11.1 micrograms (nonconvulsive) to mice of both strains resulted in similar levels of radioactivity in cortex, hippocampus, and cerebellum 30 and 60 min after injection. Bioconversion of [3H]KA to a radiolabeled brain metabolite in vivo could not be documented in mice from either strain. Results confirm previously reported differences between D2 and B6 mice in their relative susceptibility to seizures induced by systemic KA administration and suggest that these differences are not related to strain-specific variation in metabolism or BBB transport of KA. Further studies of these two strains of mice may be useful for investigating genetic influences upon seizure susceptibility.
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Affiliation(s)
- T N Ferraro
- Department of Psychiatry and Pharmacology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA 19107, USA
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Goldsmith JD, Kujawa SG, McLaren JD, Bledsoe SC. In vivo release of neuroactive amino acids from the inferior colliculus of the guinea pig using brain microdialysis. Hear Res 1995; 83:80-8. [PMID: 7607993 DOI: 10.1016/0378-5955(94)00193-t] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Microdialysis techniques were used to measure in vivo release of neuroactive amino acids from the central nucleus of the inferior colliculus (ICC) in anesthetized guinea pigs. Concentric dialysis probes were implanted in the ICC and perfused with Ringer solution of various compositions at a flow rate of 2.0 microliters/min. Consecutive 10-min fractions of the dialysate were collected for up to 3 h under different experimental conditions, frozen and assayed for amino acid content by high performance liquid chromatography (HPLC). There was an initial high outflow of amino acids which declined to stable baseline levels after 2 h. Following this stabilization period, perfusion with a medium containing 100 mM KCl produced an increase in the extracellular levels of aspartate (Asp), glutamate (Glu), gamma-aminobutyric acid (GABA) and glycine (Gly). Only the increases in GABA and Gly were statistically significant. None of the increases occurred in the presence of 2.0 mM cobalt suggesting the release of amino acids is calcium dependent. Histological examination revealed that tissue damage was minimal and largely confined to the immediate vicinity of the probes. We were also able to show that the blood brain barrier (BBB) appeared to heal 2 h after probe implantation. Thus, following intravenous injection of [3H]alpha-aminoisobutyric acid (AIB), which does not cross the intact BBB, no isotope was recovered in the dialysate. These results demonstrate that microdialysis is a unique and suitable method to monitor changes in the extracellular levels of amino acid neurotransmitters in a central auditory structure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J D Goldsmith
- Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor 48109-0506, USA
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Shneiderman A, Chase MB, Rockwood JM, Benson CG, Potashner SJ. Evidence for a GABAergic projection from the dorsal nucleus of the lateral lemniscus to the inferior colliculus. J Neurochem 1993; 60:72-82. [PMID: 8380198 DOI: 10.1111/j.1471-4159.1993.tb05824.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
This study attempts to determine whether the pathways from the guinea pig dorsal nucleus of the lateral lemniscus (DNLL) to the inferior colliculus (IC) use gamma-aminobutyric acid (GABA) as a transmitter. Injections of kainic acid (KA) were used to destroy neurons in the left DNLL. Two to 4 days after the injection, Nissl-stained sections through the lesion site showed destruction of the DNLL neurons. The lesions varied in size; 12-100% of the DNLL neurons were destroyed on the injected side without damage to the ipsilateral IC. Two to 4 days after the injection, the electrically evoked, Ca(2+)-dependent release and high-affinity uptake of [3H]GABA were measured in dissected pieces of the left and right IC. These activities were compared with those in the IC taken from unlesioned controls and from sham controls, which received injections of saline instead of KA. Each IC was divided into a dorsal piece, which contained the dorsal cortex and dorsomedial nucleus, and a ventral piece, which contained the central and lateral nuclei. Lesions of the left DNLL depressed the release and uptake of [3H]GABA in the ventral pieces of the IC, but there was a greater depression in the ventral IC contralateral to the lesioned DNLL. There were good correlations between the percentage of neuronal loss in the left DNLL and deficits in [3H]GABA release and uptake activities in the ipsi- and contralateral ventral IC. By contrast, there was no depression of [3H]GABA release and uptake in the dorsal pieces of the IC. The localization of the deficits in release and uptake appears to match the distribution of the synaptic endings of the DNLL pathways in the IC. This correspondence associates GABA release and uptake activities with the DNLL projections to the IC and, therefore, suggests that GABA may be a transmitter of these pathways. The release and uptake of [14C]glycine was also measured to determine whether glycine might be a transmitter of the DNLL pathways to the IC. Lesions of the left DNLL failed to alter the Ca(2+)-dependent release or the uptake of [14C]-glycine, suggesting that DNLL neurons are unlikely to use this compound as a transmitter.
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Affiliation(s)
- A Shneiderman
- Department of Anatomy, University of Connecticut Health Center, Farmington 06030
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Vizuete ML, Steffen V, Machado A, Cano J. Effects of neonatal enucleation on catecholamine and serotonin turnover and amino acid levels in lateral geniculate nucleus and visual cortex of the adult rat. Brain Res 1992; 575:231-7. [PMID: 1373983 DOI: 10.1016/0006-8993(92)90084-m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Changes in turnover of dopamine (DA), noradrenaline (NA) and serotonin (5-hydroxytryptamine (5-HT)) and their metabolites, together with amino acid content, have been studied in dorsal lateral geniculate nucleus (LGNd) and visual cortex (VC) of neonatal enucleated rats. Enucleation increases the 5-HT turnover in LGNd and catecholamine turnover in VC. In contrast, enucleation decreases glutamate (and/or aspartate) content in LGNd and gamma-aminobutyric acid (GABA) in VC. These changes suggest an increase of the inhibitory action of the biogenic amines in LGNd after neonatal enucleation. The decrease of GABA in VC may reflect the importance of GABA in intracortical circuitry.
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Affiliation(s)
- M L Vizuete
- Departamento de Bioquimica, Bromatologia y Toxicologia, Universidad de Sevilla, Spain
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Strolin Benedetti M, Kettler R, Marrari P, Cini M, Da Prada M, Dostert P. The effects of lifelong treatment with MAO inhibitors on amino acid levels in rat brain. JOURNAL OF NEURAL TRANSMISSION. PARKINSON'S DISEASE AND DEMENTIA SECTION 1990; 2:239-48. [PMID: 2078306 DOI: 10.1007/bf02252919] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In a previous paper a possible relationship had been suggested to exist between age-induced changes in total MAO activity and amino acid levels in some rat brain areas. To further investigate the possible involvement of MAO activity in changes of brain amino acid levels with aging, moclobemide and Ro 19-6327, short acting MAO-A and MAO-B inhibitors, respectively, were administered to female Wistar rats for their whole life-span. Brain amino acid levels in animals treated with MAO inhibitors were compared to those of young and old nontreated rats. The age-induced changes in brain amino acid concentrations found in the present study were in good agreement with those previously reported. Treatment with both moclobemide and Ro 19-6327 was found to restore taurine and serine concentrations in cortex and glutamine concentrations in cerebellum, to the same values as in young rats, to decrease cerebellum concentrations of serine and to increase taurine concentrations in hypothalamus. Administration of moclobemide brought aspartate concentrations in accumbens and cortex back to the same values as in young rats. A similar effect was observed on hypothalamus glutamate concentrations in rats treated with Ro 19-6327. Some possible causes and consequences of the correction of age-induced brain amino acid levels by chronic administration of MAO inhibitors are discussed.
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