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A dynamic role for dopamine receptors in the control of mammalian spinal networks. Sci Rep 2020; 10:16429. [PMID: 33009442 PMCID: PMC7532218 DOI: 10.1038/s41598-020-73230-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 09/11/2020] [Indexed: 12/21/2022] Open
Abstract
Dopamine is well known to regulate movement through the differential control of direct and indirect pathways in the striatum that express D1 and D2 receptors respectively. The spinal cord also expresses all dopamine receptors; however, how the specific receptors regulate spinal network output in mammals is poorly understood. We explore the receptor-specific mechanisms that underlie dopaminergic control of spinal network output of neonatal mice during changes in spinal network excitability. During spontaneous activity, which is a characteristic of developing spinal networks operating in a low excitability state, we found that dopamine is primarily inhibitory. We uncover an excitatory D1-mediated effect of dopamine on motoneurons and network output that also involves co-activation with D2 receptors. Critically, these excitatory actions require higher concentrations of dopamine; however, analysis of dopamine concentrations of neonates indicates that endogenous levels of spinal dopamine are low. Because endogenous levels of spinal dopamine are low, this excitatory dopaminergic pathway is likely physiologically-silent at this stage in development. In contrast, the inhibitory effect of dopamine, at low physiological concentrations is mediated by parallel activation of D2, D3, D4 and α2 receptors which is reproduced when endogenous dopamine levels are increased by blocking dopamine reuptake and metabolism. We provide evidence in support of dedicated spinal network components that are controlled by excitatory D1 and inhibitory D2 receptors that is reminiscent of the classic dopaminergic indirect and direct pathway within the striatum. These results indicate that network state is an important factor that dictates receptor-specific and therefore dose-dependent control of neuromodulators on spinal network output and advances our understanding of how neuromodulators regulate neural networks under dynamically changing excitability.
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Potter LE, Doolen S, Mifflin K, Tenorio G, Baker G, Taylor BK, Kerr BJ. Antinociceptive Effects of the Antidepressant Phenelzine are Mediated by Context-Dependent Inhibition of Neuronal Responses in the Dorsal Horn. Neuroscience 2018; 383:205-215. [PMID: 29752984 DOI: 10.1016/j.neuroscience.2018.04.047] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 04/23/2018] [Accepted: 04/28/2018] [Indexed: 02/08/2023]
Abstract
The putative strong anti-nociceptive properties of the antidepressant phenelzine (PLZ) have not been widely explored as a treatment for pain. Antinociceptive effects of PLZ were identified in the formalin model of tonic pain (Mifflin et al., 2016) and in allodynia associated with experimental autoimmune encephalomyelitis, (EAE) a mouse model of multiple sclerosis (Potter et al., 2016). Here, we further clarify the specific types of stimuli and contexts in which PLZ modulates nociceptive sensitivity. Our findings indicate that PLZ selectively inhibits ongoing inflammatory pain while sparing transient reflexive and acute nociception. We also investigated the cellular mechanisms of action of PLZ in the dorsal horn, and as expected of a monoamine-oxidase inhibitor, PLZ increased serotonin (5HT) immunoreactivity. We next used two approaches to test the hypothesis that PLZ inhibits the activation of spinal nociresponsive neurons. First, we evaluated the formalin-evoked protein expression of the immediate early gene, c-fos. PLZ reduced Fos expression in the superficial dorsal horn. Second, we evaluated the effects of PLZ on intracellular calcium responses to superfusion of glutamate (0.3-1.0 mM) in an ex vivo lumbar spinal cord slice preparation. Superfusion with PLZ (100-300 μM) reduced 1 mM glutamate-evoked calcium responses. This was blocked by pretreatment with the 5HT1A-receptor antagonist WAY-100,635, but not the alpha-2 adrenergic antagonist idazoxan. We conclude that PLZ exerts antinociceptive effects through a 5-HT/5HT1AR-dependent inhibition of neuronal responses within nociceptive circuits of the dorsal horn.
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Affiliation(s)
- Liam E Potter
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Suzanne Doolen
- Department of Physiology and the Center for Analgesia Research Excellence, University of Kentucky, Lexington, KY 40536, USA
| | - Katherine Mifflin
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Department of Psychology, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Gustavo Tenorio
- Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB T6G 2G3, Canada
| | - Glen Baker
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Department of Psychiatry (NRU), University of Alberta, Edmonton, AB T6G 2B7, Canada
| | - Bradley K Taylor
- Department of Physiology and the Center for Analgesia Research Excellence, University of Kentucky, Lexington, KY 40536, USA
| | - Bradley J Kerr
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Department of Pharmacology, University of Alberta, Edmonton, AB T6E 2H7, Canada; Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB T6G 2G3, Canada.
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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
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Potter LE, Paylor JW, Suh JS, Tenorio G, Caliaperumal J, Colbourne F, Baker G, Winship I, Kerr BJ. Altered excitatory-inhibitory balance within somatosensory cortex is associated with enhanced plasticity and pain sensitivity in a mouse model of multiple sclerosis. J Neuroinflammation 2016; 13:142. [PMID: 27282914 PMCID: PMC4901403 DOI: 10.1186/s12974-016-0609-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 06/01/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Chronic neuropathic pain is a common symptom of multiple sclerosis (MS). MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) has been used as an animal model to investigate the mechanisms of pain in MS. Previous studies have implicated sensitization of spinal nociceptive networks in the pathogenesis of pain in EAE. However, the involvement of supraspinal sites of nociceptive integration, such as the primary somatosensory cortex (S1), has not been defined. We therefore examined functional, structural, and immunological alterations in S1 during the early stages of EAE, when pain behaviors first appear. We also assessed the effects of the antidepressant phenelzine (PLZ) on S1 alterations and nociceptive (mechanical) sensitivity in early EAE. PLZ has been shown to restore central nervous system (CNS) tissue concentrations of GABA and the monoamines (5-HT, NA) in EAE. We hypothesized that PLZ treatment would also normalize nociceptive sensitivity in EAE by restoring the balance of excitation and inhibition (E-I) in the CNS. METHODS We used in vivo flavoprotein autofluorescence imaging (FAI) to assess neural ensemble responses in S1 to vibrotactile stimulation of the limbs in early EAE. We also used immunohistochemistry (IHC), and Golgi-Cox staining, to examine synaptic changes and neuroinflammation in S1. Mechanical sensitivity was assessed at the clinical onset of EAE with Von Frey hairs. RESULTS Mice with early EAE exhibited significantly intensified and expanded FAI responses in S1 compared to controls. IHC revealed increased vesicular glutamate transporter (VGLUT1) expression and disrupted parvalbumin+ (PV+) interneuron connectivity in S1 of EAE mice. Furthermore, peri-neuronal nets (PNNs) were significantly reduced in S1. Morphological analysis of excitatory neurons in S1 revealed increased dendritic spine densities. Iba-1+ cortical microglia were significantly elevated early in the disease. Chronic PLZ treatment was found to normalize mechanical thresholds in EAE. PLZ also normalized S1 FAI responses, neuronal morphologies, and cortical microglia numbers and attenuated VGLUT1 reactivity-but did not significantly attenuate the loss of PNNs. CONCLUSIONS These findings implicate a pro-excitatory shift in the E-I balance of the somatosensory CNS, arising early in the pathogenesis EAE and leading to large-scale functional and structural plasticity in S1. They also suggest a novel antinociceptive effect of PLZ treatment.
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Affiliation(s)
- Liam E Potter
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Anesthesiology and Pain Medicine, University of Alberta, Clinical Sciences Building, 8-120, Edmonton, AB, T6G 2G3, Canada
| | - John W Paylor
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Psychiatry (NRU), University of Alberta, Edmonton, AB, T6G 2B7, Canada
| | - Jee Su Suh
- Department of Anesthesiology and Pain Medicine, University of Alberta, Clinical Sciences Building, 8-120, Edmonton, AB, T6G 2G3, Canada
| | - Gustavo Tenorio
- Department of Anesthesiology and Pain Medicine, University of Alberta, Clinical Sciences Building, 8-120, Edmonton, AB, T6G 2G3, Canada
| | - Jayalakshmi Caliaperumal
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Psychology, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Fred Colbourne
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Psychology, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Glen Baker
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Psychiatry (NRU), University of Alberta, Edmonton, AB, T6G 2B7, Canada
| | - Ian Winship
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Psychiatry (NRU), University of Alberta, Edmonton, AB, T6G 2B7, Canada
| | - Bradley J Kerr
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada. .,Department of Pharmacology, University of Alberta, Edmonton, AB, T6E 2H7, Canada. .,Department of Anesthesiology and Pain Medicine, University of Alberta, Clinical Sciences Building, 8-120, Edmonton, AB, T6G 2G3, Canada.
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Benson CA, Wong G, Tenorio G, Baker GB, Kerr BJ. The MAO inhibitor phenelzine can improve functional outcomes in mice with established clinical signs in experimental autoimmune encephalomyelitis (EAE). Behav Brain Res 2013; 252:302-11. [DOI: 10.1016/j.bbr.2013.06.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 06/07/2013] [Accepted: 06/11/2013] [Indexed: 12/18/2022]
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The amine oxidase inhibitor phenelzine limits lipogenesis in adipocytes without inhibiting insulin action on glucose uptake. J Neural Transm (Vienna) 2012; 120:997-1003. [DOI: 10.1007/s00702-012-0951-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Accepted: 12/04/2012] [Indexed: 12/22/2022]
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Simpson SM, Hickey AJ, Baker GB, Reynolds JN, Beninger RJ. The antidepressant phenelzine enhances memory in the double Y-maze and increases GABA levels in the hippocampus and frontal cortex of rats. Pharmacol Biochem Behav 2012; 102:109-17. [DOI: 10.1016/j.pbb.2012.03.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 03/20/2012] [Accepted: 03/28/2012] [Indexed: 11/17/2022]
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Musgrave T, Benson C, Wong G, Browne I, Tenorio G, Rauw G, Baker GB, Kerr BJ. The MAO inhibitor phenelzine improves functional outcomes in mice with experimental autoimmune encephalomyelitis (EAE). Brain Behav Immun 2011; 25:1677-88. [PMID: 21723939 DOI: 10.1016/j.bbi.2011.06.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/13/2011] [Accepted: 06/15/2011] [Indexed: 02/06/2023] Open
Abstract
Multiple sclerosis (MS) and the animal model, experimental autoimmune encephalomyelitis (EAE), are both accompanied by motor and non-motor symptoms. Pathological changes in the activities of key neurotransmitters likely underlie many of these symptoms. We have previously described disturbances in the levels of 5-hydroxytryptamine (5-HT/serotonin), noradrenaline (NE) and γ-aminobutyric acid (GABA) in a mouse model of EAE. The potential therapeutic effect of a drug that targets these three neurotransmitters, the antidepressant and anti-panic drug phenelzine (PLZ), was assessed in mice with MOG(35-55) induced EAE. The neurotransmitter content of EAE and control tissue after PLZ administration was first evaluated by HPLC. The ability of PLZ treatment to modulate EAE disease course and clinical signs was then assessed. Daily PLZ treatment, starting seven days after disease induction, delayed EAE onset, reduced disease severity in the chronic phase and was associated with substantial improvements in exploratory behavior and a novel measure of sickness and/or depression. Upon completion of the experiment, PLZ's effects on histopathological markers of the disease were examined. No differences were observed in T cell infiltration, microglia/macrophage reactivity, demyelination or axonal injury in PLZ-treated spinal cords. However, EAE mice treated with PLZ showed a normalization of 5-HT levels in the ventral horn of the spinal cord that might account for the improvements in behavioral outcomes. These results demonstrate the therapeutic potential of MAO inhibitors such as PLZ in MS. Additionally, the behavioral changes observed in EAE mice indicate that alterations in non-motor or 'affective' measures may be valuable to consider in addition to traditional measures of gross locomotor function.
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Affiliation(s)
- Travis Musgrave
- Centre for Neuroscience, University of Alberta, Edmonton, AB, Canada
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Del'guidice T, Lemasson M, Beaulieu JM. Role of Beta-arrestin 2 downstream of dopamine receptors in the Basal Ganglia. Front Neuroanat 2011; 5:58. [PMID: 21922001 PMCID: PMC3167352 DOI: 10.3389/fnana.2011.00058] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 08/17/2011] [Indexed: 12/26/2022] Open
Abstract
Multifunctional scaffolding protein beta-arrestins (βArr) and the G protein-receptor kinases are involved in the desensitization of several G protein-coupled receptors (GPCR). However, arrestins can also contribute to GPCR signaling independently from G proteins. In this review, we focus on the role of βArr in the regulation of dopamine receptor functions in the striatum. First, we present in vivo evidence supporting a role for these proteins in the regulation of dopamine receptor desensitization. Second, we provide an overview of the roles of βArr2 in the regulation of extracellular-signal-regulated kinases/MAP kinases and Akt/GSK3 signaling pathways downstream of the D1 and D2 dopamine receptors. Thereafter, we examine the possible involvement of βArr-mediated signaling in the action of dopaminergic drugs used for the treatment of mental disorders. Finally, we focus on different potential cellular proteins regulated by βArr-mediated signaling which could contribute to the regulation of behavioral responses to dopamine. Overall, the identification of a cell signaling function for βArr downstream of dopamine receptors underscores the intricate complexity of the intertwined mechanisms regulating and mediating cell signaling in the basal ganglia. Understanding these mechanisms may lead to a better comprehension of the several roles played by these structures in the regulation of mood and to the development of new psychoactive drugs having better therapeutic efficacy.
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Affiliation(s)
- Thomas Del'guidice
- Department of Psychiatry and Neuroscience, Faculty of Medicine, Centre de Recherche Université Laval Robert-Giffard Québec, QC, Canada
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Andrews PW, Kornstein SG, Halberstadt LJ, Gardner CO, Neale MC. Blue again: perturbational effects of antidepressants suggest monoaminergic homeostasis in major depression. Front Psychol 2011; 2:159. [PMID: 21779273 PMCID: PMC3133866 DOI: 10.3389/fpsyg.2011.00159] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 06/23/2011] [Indexed: 12/15/2022] Open
Abstract
Some evolutionary researchers have argued that current diagnostic criteria for major depressive disorder (MDD) may not accurately distinguish true instances of disorder from a normal, adaptive stress response. According to disorder advocates, neurochemicals like the monoamine neurotransmitters (serotonin, norepinephrine, and dopamine) are dysregulated in major depression. Monoamines are normally under homeostatic control, so the monoamine disorder hypothesis implies a breakdown in homeostatic mechanisms. In contrast, adaptationist hypotheses propose that homeostatic mechanisms are properly functioning in most patients meeting current criteria for MDD. If the homeostatic mechanisms regulating monoamines are functioning properly in these patients, then oppositional tolerance should develop with prolonged antidepressant medication (ADM) therapy. Oppositional tolerance refers to the forces that develop when a homeostatic mechanism has been subject to prolonged pharmacological perturbation that attempt to bring the system back to equilibrium. When pharmacological intervention is discontinued, the oppositional forces cause monoamine levels to overshoot their equilibrium levels. Since depressive symptoms are under monoaminergic control, this overshoot should cause a resurgence of depressive symptoms that is proportional to the perturbational effect of the ADM. We test this prediction by conducting a meta-analysis of ADM discontinuation studies. We find that the risk of relapse after ADM discontinuation is positively associated with the degree to which ADMs enhance serotonin and norepinephrine in prefrontal cortex, after controlling for covariates. The results are consistent with oppositional tolerance, and provide no evidence of malfunction in the monoaminergic regulatory mechanisms in patients meeting current diagnostic criteria for MDD. We discuss the evolutionary and clinical implications of our findings.
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Affiliation(s)
- Paul W. Andrews
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth UniversityRichmond, VA, USA
- Department of Psychology, Neuroscience and Behaviour, McMaster UniversityHamilton, ON, Canada
| | - Susan G. Kornstein
- Department of Psychiatry, Virginia Commonwealth UniversityRichmond, VA, USA
| | - Lisa J. Halberstadt
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth UniversityRichmond, VA, USA
| | - Charles O. Gardner
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth UniversityRichmond, VA, USA
| | - Michael C. Neale
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth UniversityRichmond, VA, USA
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Yin HS, Chen K, Shih JC, Tien TW. Down-regulated GABAergic expression in the olfactory bulb layers of the mouse deficient in monoamine oxidase B and administered with amphetamine. Cell Mol Neurobiol 2010; 30:511-9. [PMID: 19902350 PMCID: PMC2875355 DOI: 10.1007/s10571-009-9475-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 10/20/2009] [Indexed: 12/29/2022]
Abstract
This study explores primarily the role of the activity of monoamine oxidase B (MAOB) in the regulation of glutamic acid decarboxylase(67) (GAD(67)) expression in distinct layers of main olfactory bulb (OlfB), which links the limbic system. Moreover, the response of GAD(67) was investigated to amphetamine perturbation in the absence of MAOB activity. Immunocytochemical analysis was performed on OlfB sections prepared from the adult wild type (WT) and the MAOB gene-knocked-out (KO) mice after receiving repeated intraperitoneal injections (two doses per day, total seven doses) of saline or amphetamine, 5 mg/kg. The levels of the GAD(67) immunoreactivity were approximate 25 and 38% lower in respective glomerular (GloL) and mitral cell layers (ML) of saline-treated KO mice than that of WT, whereas similar in the external plexiform or granule cell layers (GraL) of the KO and WT. In the GloL, the level of tyrosine hydroxylase was 39% lower in the KO mice than WT, implicating different dopamine content in the KO from WT. The amphetamine exposure down-regulated the levels of GAD(67) in the WT layers by 46 to 52%, and in KO layers 65 to 71%, except ML. The GraL GAD(67) level may be regulated by the activation of CREB, as the phosphorylated (p) CREB coexisted with GAD(67), and the percentage of GAD(67)-expressing pCREB neurons was decreased by the amphetamine exposure. The data indicate that the activity of MAOB could modulate the regular and amphetamine-perturbed expression of GAD(67) and pCREB. Thus, interactions are suggested among the MAOB activity, GABA content of OlfB, and olfaction.
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Affiliation(s)
- Hsiang-Shu Yin
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, 100, Taiwan, ROC.
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Simultaneous determination of 5-hydroxyindoles and catechols from urine using polymer monolith microextraction coupled to high-performance liquid chromatography with fluorescence detection. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 877:1847-55. [DOI: 10.1016/j.jchromb.2009.05.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Revised: 04/30/2009] [Accepted: 05/07/2009] [Indexed: 11/24/2022]
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Elevated endogenous GABA concentration attenuates glutamate-glutamine cycling between neurons and astroglia. J Neural Transm (Vienna) 2009; 116:291-300. [PMID: 19184333 DOI: 10.1007/s00702-009-0186-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 01/13/2009] [Indexed: 10/21/2022]
Abstract
In this study, the relationship between endogenous brain GABA concentration and glutamate-glutamine cycling flux (V (cyc)) was investigated using in vivo (1)H and (1)H{(13)C} magnetic resonance spectroscopy techniques. Graded elevations of brain GABA levels were induced in rat brain after administration of the highly specific GABA-transaminase inhibitor vigabatrin (gamma-vinyl-GABA). The glial-specific substrate [2-(13)C]acetate and (1)H{(13)C} magnetic resonance spectroscopy were used to measure V (cyc) at different GABA levels. Significantly reduced V (cyc) was found in rats pretreated with vigabatrin. The reduction in group mean V (cyc) over the range of GABA concentrations investigated in this study (1.0 +/- 0.3-5.1 +/- 0.5 micromol/g) was found to be nonlinear: Delta V (cyc)/V (cyc) = [GABA (micromol/g)](-0.35 )- 1.0 (r (2) = 0.98). The results demonstrate that V (cyc) is modulated by endogenous GABA levels, and that glutamatergic and GABAergic interactions can be studied in vivo using noninvasive magnetic resonance spectroscopy techniques.
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N-Propynyl analogs of β-phenylethylidenehydrazines: Synthesis and evaluation of effects on glycine, GABA, and monoamine oxidase. Bioorg Med Chem 2008; 16:8254-63. [DOI: 10.1016/j.bmc.2008.07.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 07/14/2008] [Accepted: 07/14/2008] [Indexed: 11/17/2022]
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Pollack MH, Jensen JE, Simon NM, Kaufman RE, Renshaw PF. High-field MRS study of GABA, glutamate and glutamine in social anxiety disorder: response to treatment with levetiracetam. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:739-43. [PMID: 18206286 DOI: 10.1016/j.pnpbp.2007.11.023] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 11/14/2007] [Accepted: 11/20/2007] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Abnormalities in brain gamma-aminobutyric acid (GABA) and glutamate may be relevant to the underlying pathophysiology of anxiety disorders including social anxiety disorder (SAD). METHODS We used proton magnetic resonance spectroscopy (pMRS) to examine whole brain and regional GABA, glutamate and glutamine in patients (N=10) with SAD at baseline compared to a matched group of healthy controls (HC), and changes following 8 weeks of pharmacotherapy with levetiracetam. RESULTS For SAD subjects, there were significantly higher whole brain levels of glutamate and glutamine, though no significant differences in GABA. In the thalamus, glutamine was higher and GABA lower for SAD subjects. There was a significant reduction in thalamic glutamine with levetiracetam treatment. CONCLUSION Our findings provide preliminary support for impaired GABAergic and overactive glutamatergic function in social anxiety disorder and the potential relevance of changes in these systems for the anxiolytic response to levetiracetam.
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Affiliation(s)
- Mark H Pollack
- Psychiatry Department, Massachusetts General Hospital, Boston, MA 02114, United States.
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MacKenzie EM, Grant SL, Baker GB, Wood PL. Phenelzine causes an increase in brain ornithine that is prevented by prior monoamine oxidase inhibition. Neurochem Res 2007; 33:430-6. [PMID: 17768678 DOI: 10.1007/s11064-007-9448-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Accepted: 07/17/2007] [Indexed: 11/30/2022]
Abstract
Phenelzine (PLZ), a nonselective irreversible inhibitor of monoamine oxidase (MAO), also inhibits GABA-transaminase (GABA-T), markedly increasing brain GABA levels. PLZ is also a substrate for MAO, and studies suggest that a metabolite formed by the action of this enzyme on PLZ may be responsible for the increase in GABA observed. We have recently found that PLZ also elevates brain ornithine (ORN), an amino acid precursor to both glutamate (and GABA) and the polyamines, and have conducted dose- and time-response studies on this effect. Rats were treated with vehicle or PLZ doses (7.5, 15 or 30 mg/kg i.p.), and brains were collected 3 h later. In the time-response study, animals were treated with vehicle or PLZ (15 mg/kg i.p.) and brains were collected 1-24 h later. To determine whether a metabolite formed by the action of MAO on PLZ may be responsible for the elevation in brain ORN observed, animals were pretreated with vehicle or the MAO inhibitor tranylcypromine (TCP) before vehicle or PLZ (15 mg/kg), and brains collected 3 h later. ORN levels (measured by an HPLC procedure) were dose- and time-dependently increased in PLZ-treated animals, with levels reaching approximately 650% of control at 6 and 12 h. Pretreatment with TCP completely abolished the PLZ-induced increase in brain ORN, suggesting, as with GABA, that a metabolite of PLZ formed by the action of MAO is responsible for the elevation of brain ORN observed. The possible contribution of increased ORN to therapeutic and/or neuroprotective properties of PLZ is discussed.
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Affiliation(s)
- Erin M MacKenzie
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, 1E7.31 Walter MacKenzie Centre, Edmonton, AB, Canada T6G 2R7
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Yin HS, Chen K, Kalpana S, Shih JC. Differential effects of chronic amphetamine and baclofen administration on cAMP levels and phosphorylation of CREB in distinct brain regions of wild type and monoamine oxidase B-deficient mice. Synapse 2007; 60:573-84. [PMID: 16983645 DOI: 10.1002/syn.20334] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Roles of GABA(B) transmission were explored in the action of amphetamine (Amph) on the brain. Adult male wild type (WT) and monoamine oxidase B-knocked out (MAOBKO) mice received i.p. injections of saline, d-Amph (5 mg/kg), plus baclofen (GABA(B) receptor agonist, 10 mg/kg), or baclofen and Amph, twice daily for 3 days and single treatments on day 4, followed by immuno-cyclic-AMP (cAMP) and immunoblotting assays on the brain tissue. The WT mice responded with higher levels of behavioral responses than the KO to the daily Amph injection; however, baclofen blocked the Amph-induced behavioral hyperactivity of both WT and KO mice. After the last treatment, levels of cAMP and phosphorylated (p) cyclic-AMP response element binding protein (CREB) were up-regulated in the striatum and somatosensory cortex of Amph-treated WT mice, while similar to the saline-controls in the baclofen+Amph-treated group, indicating the blockade by baclofen to Amph. Baclofen similarly suppressed the Amph-induced increases in pCREB levels of WT hippocampus and amygdala, and decreases of olfactory bulb and thalamus. For MAOBKO mice, baclofen hindered the Amph-generated increases in motor cortical cAMP and pCREB, and amygdaloid pCREB, and the decrease in olfactory bulb pCREB, whereas did not affect the Amph-raised hippocampal pCREB. Furthermore, the levels of CREB were variably modified in distinct regions by the drug exposures. The data reveal that the GABA(B)-mediated intracellular signaling differentially participates in mechanisms underlying Amph perturbation to various regions, and may thereby contribute explanations to the behavioral consequences. Moreover, MAOB is region-dependently involved in responses of the brain to Amph and baclofen, supporting interactions between GABA and monoamines.
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Affiliation(s)
- Hsiang-Shu Yin
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan.
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19
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Kalueff AV. Neurobiology of memory and anxiety: from genes to behavior. Neural Plast 2007; 2007:78171. [PMID: 17502911 PMCID: PMC1847471 DOI: 10.1155/2007/78171] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 11/15/2006] [Accepted: 11/16/2006] [Indexed: 01/18/2023] Open
Abstract
Interaction of anxiety and memory represents an essential feature of CNS functioning. This paper reviews experimental data coming from neurogenetics, neurochemistry, and behavioral pharmacology (as well as parallel clinical findings) reflecting different mechanisms of memory-anxiety interplay, including brain neurochemistry, circuitry, pharmacology, neuroplasticity, genes, and gene-environment interactions. It emphasizes the complexity and nonlinearity of such interplay, illustrated by a survey of anxiety and learning/memory phenotypes in various genetically modified mouse models that exhibit either synergistic or reciprocal effects of the mutation on anxiety levels and memory performance. The paper also assesses the putative role of different neurotransmitter systems and neuropeptides in the regulation of memory processes and anxiety, and discusses the role of neural plasticity in these mechanisms.
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Affiliation(s)
- Allan V Kalueff
- Laboratory of Clinical Science, Division of Intramural Research Program, National Institute of Mental Health , Bethesda, MD 20892-1264, USA.
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20
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Gatch MB, Taylor CM, Flores E, Selvig M, Forster MJ. Effects of monoamine oxidase inhibitors on cocaine discrimination in rats. Behav Pharmacol 2006; 17:151-9. [PMID: 16495723 PMCID: PMC3867205 DOI: 10.1097/01.fbp.0000197459.08892.b5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This study tested the time course of the discriminative stimulus effects of inhibitors of monoamine oxidase alone or in combination with cocaine. Male Sprague-Dawley rats were trained to discriminate cocaine (10 mg/kg, intraperitoneal) from saline using a two-lever choice methodology. The nonselective monoamine oxidase inhibitors tranylcypromine (0.01-5 mg/kg) and phenelzine (1-25 mg/kg), the monoamine oxidase-A selective compound clorgyline (1-25 mg/kg), and the monoamine oxidase-B selective compounds pargyline (0.005-50 mg/kg) and selegiline (1-25 mg/kg) were tested for substitution 15 min or 24 h following administration, and in combination with 10 mg/kg of cocaine 24 and 48 h after administration. At 15 min, selegiline fully substituted for the discriminative stimulus effects of cocaine, whereas all other compounds partially substituted. At 24 h, substitution of cocaine was diminished for all compounds except phenelzine, which produced a greater amount of substitution at 24 h than at 15 min. When cocaine was administered 24 h after clorgyline, selegiline, pargyline, and phenelzine, cocaine-appropriate responding was attenuated at intermediate doses of these drugs, whereas the highest doses did not alter cocaine-lever responding. All compounds except selegiline substantially decreased response rate and produced various adverse effects. At 48 h, the effects of all compounds except phenelzine were markedly reduced. Selectivity for monoamine oxidase-A or monoamine oxidase-B did not predict the ability to substitute for or attenuate the subjective effects of cocaine. These findings suggest that monoamine oxidase inhibitors can modulate the discriminative stimulus effects of cocaine for at least 24 h, and may be useful for treatment of cocaine abuse.
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Affiliation(s)
- Michael B Gatch
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas 76107-2699, USA.
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21
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Guillem K, Vouillac C, Azar MR, Parsons LH, Koob GF, Cador M, Stinus L. Monoamine oxidase inhibition dramatically increases the motivation to self-administer nicotine in rats. J Neurosci 2006; 25:8593-600. [PMID: 16177026 PMCID: PMC6725504 DOI: 10.1523/jneurosci.2139-05.2005] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nicotine is the major neuroactive compound of tobacco, which has, by itself, weak reinforcing properties. It is known that levels of the enzymes monoamine oxidase A (MAO-A) and MAO-B are reduced in the platelets and brains of smokers and that substances, other than nicotine, present in tobacco smoke have MAO-inhibitory activities. Here, we report that inhibition of MAO dramatically and specifically increases the motivation to self-administer nicotine in rats. These effects were more prominent in rats selected for high responsiveness to novelty than in rats with low responsiveness to novelty. The results suggest that the inhibition of MAO activity by compounds present in tobacco smoke may combine with nicotine to produce the intense reinforcing properties of cigarette smoking that lead to addiction.
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Affiliation(s)
- Karine Guillem
- Laboratoire de Neuropsychobiologie des Désadaptations, Unité Mixte de Recherche 5541, Centre National de la Recherche Scientifique, Université de Bordeaux 2, 33076 Bordeaux Cedex, France
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22
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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.
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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
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23
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Yoshitake T, Kehr J, Yoshitake S, Fujino K, Nohta H, Yamaguchi M. Determination of serotonin, noradrenaline, dopamine and their metabolites in rat brain extracts and microdialysis samples by column liquid chromatography with fluorescence detection following derivatization with benzylamine and 1,2-diphenylethylenediamine. J Chromatogr B Analyt Technol Biomed Life Sci 2004; 807:177-83. [PMID: 15203027 DOI: 10.1016/j.jchromb.2004.03.069] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2004] [Revised: 03/24/2004] [Accepted: 03/25/2004] [Indexed: 11/24/2022]
Abstract
A highly selective and sensitive column liquid chromatographic method for fluorescence determination of serotonin (5-HT), dopamine (DA), noradrenaline (NA) and their related metabolites 5-hydroxyindole-3-acetic acid (5-HIAA) and 3,4-dihydroxyphenylacetic acid (DOPAC) following derivatization with benzylamine and 1,2-diphenylethylenediamine (DPE) is described. The monoamines and the metabolites (20 microl samples) were derivatized in a two-step reaction, initiated with 20 microl of 0.3M benzylamine in 0.3M 3-cyclohexylaminopropanesulfonic acid (CAPS) buffer (pH 10.0), (for 5-HT, 5-HIAA, 2 min, 24 degrees C) and followed by 20 microl of 0.1M DPE in 0.3M glycine buffer (pH 10.0), (for DA, NA, DOPAC, 20 min, 50 degrees C). Both reagents contained 0.02 M potassium hexacyanoferrate(III) and 50% (v/v) methanol. The resulting highly fluorescent and stable benzoxazole derivatives were isocratically separated on a reversed-phase column (150 mm x 1.5 mm i.d., packed with C18 silica, 5 microm) within 45 min. Using fluorescence detection at ex. and em. wavelengths of 345 and 480 nm, respectively, the detection limit (signal-to-noise ratio of 3) for 5-HT, DA, NA, 5-HIAA, L-DOPA and DOPAC ranged between 0.08 and 5.65 fmol per 20-microl injection (12-847.5 pM in standard solution). The concentrations of monoamines (expressed in microg/g wet weight, mean +/- S.E.M., n=5) in tissue extracts from the rat striatum were: 0.45+/-0.05 (5-HT), 4.27+/-0.08 (DA), 0.27+/-0.04 (NA), 0.55+/-0.06 (5-HIAA), 1.26+/-0.16 (L-DOPA) and 1.62+/-0.11 (DOPAC). Microdialysis samples were collected in 20 min intervals from the probes implanted in the striatum of awake rats. The basal monoamine levels (in fmol/20 microl, mean +/- S.E.M., n=5) in the dialysates were: 4.0+/-0.7 (5-HT), 78.4+/-9.1 (DA), 6.4+/-0.8 (NA), 785.5+/-64.5 (5-HIAA) and 5504.5+/-136.5 (DOPAC). It is concluded that the new fluorescence derivatization protocol provides an excellent means for simultaneous determination of all three monoamines both in the complex samples (e.g. brain homogenates) and also at trace levels, such as those found in the microdialysis samples.
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Affiliation(s)
- Takashi Yoshitake
- Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden
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24
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Damberg M, Berggård C, Oreland L. Phenelzine treatment increases transcription factor AP-2 levels in rat brain. BMC Pharmacol 2003; 3:10. [PMID: 12943557 PMCID: PMC194722 DOI: 10.1186/1471-2210-3-10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Accepted: 08/28/2003] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The elevations of noradrenaline (NA) and serotonin (5-HT) levels in response to acute serotonin reuptake inhibitor (SSRI) or tricyclic antidepressant (TCA) exposure are not consistent with the time course for the therapeutic action of these antidepressants. Thus, neuronal adaptations are needed for the therapeutic effect to arise. Transcription factor Activating Protein -2 (AP-2) is critical for mammalian neural gene expression. Several genes involved in brainstem CNS transmitter systems, especially the monoamines, have AP-2 binding sites in their regulatory regions. We have previously shown that treatment with citalopram and imipramin resulted in a decrease in AP-2alpha and AP-2beta levels in rat brain. We have also reported an association between a specific genotype of AP-2beta to personality traits, binge-eating disorder and platelet monoamine oxidase (MAO) activity. RESULTS Subchronic administration (10 days) of phenelzine (PLZ) increased the levels of AP-2alpha, AP-2beta and the DNA binding activity of AP-2 in nuclear extracts prepared from rat whole brain when compared with sham treated animals. CONCLUSION These data suggest that AP-2 is not involved in the therapeutic effect of antidepressants. Rather, the effects of antidepressants seen on the levels of AP-2 might be involved in the expression of side-effects during the lag-period.
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Affiliation(s)
- Mattias Damberg
- Department of Neuroscience, Section of Pharmacology, Uppsala University, Uppsala, Sweden
| | - Cecilia Berggård
- Department of Neuroscience, Section of Pharmacology, Uppsala University, Uppsala, Sweden
| | - Lars Oreland
- Department of Neuroscience, Section of Pharmacology, Uppsala University, Uppsala, Sweden
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25
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Abstract
The authors review the available literature on the preclinical and clinical studies involving GABAergic neurotransmission in mood disorders. Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter present almost exclusively in the central nervous system (CNS), distributed across almost all brain regions, and expressed in interneurons modulating local circuits. The role of GABAergic dysfunction in mood disorders was first proposed 20 years ago. Preclinical studies have suggested that GABA levels may be decreased in animal models of depression, and clinical studies reported low plasma and CSF GABA levels in mood disorder patients. Also, antidepressants, mood stabilizers, electroconvulsive therapy, and GABA agonists have been shown to reverse the depression-like behavior in animal models and to be effective in unipolar and bipolar patients by increasing brain GABAergic activity. The hypothesis of reduced GABAergic activity in mood disorders may complement the monoaminergic and serotonergic theories, proposing that the balance between multiple neurotransmitter systems may be altered in these disorders. However, low GABAergic cortical function may probably be a feature of a subset of mood disorder patients, representing a genetic susceptibility. In this paper, we discuss the status of GABAergic hypothesis of mood disorders and suggest possible directions for future preclinical and clinical research in this area.
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Affiliation(s)
- P Brambilla
- Biological Psychiatry Unit, IRCCS S Giovanni di Dio, Fatebenefratelli, Brescia, Italy.
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26
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Pizzinat N, Marchal-Victorion S, Maurel A, Ordener C, Bompart G, Parini A. Substrate-dependent regulation of MAO-A in rat mesangial cells: involvement of dopamine D2-like receptors. Am J Physiol Renal Physiol 2003; 284:F167-74. [PMID: 12388421 DOI: 10.1152/ajprenal.00113.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we investigated the existence of a back-regulation of the catecholamine-degrading enzyme monoamine oxidase (MAO)-A by dopamine in rat renal cells. In proximal tubule cells, MAO-A expression was not modified after dopamine receptor stimulation. In contrast, in mesangial cells, enzyme assay and Western blots showed that MAO activity and protein increased by approximately 80% after 48-h incubation with the D(2)-like receptor agonist bromocriptine and quinpirole but not with the D(1)-like receptor agonist SKF-38393. This effect was prevented by the D(2)-receptor antagonist sulpiride and domperidone. The increase in MAO-A protein was preceded by an augmentation of MAO-A mRNA that was prevented by the transcriptional inhibitor actinomycin D. Bromocriptine effect was mimicked by the PKA inhibitor H89 and inhibited by the PKA activator 8-bromo-cAMP. These results show for the first time the existence of a dopamine-dependent MAO-A regulation involving D(2)-like receptors, inhibition of the cAMP-PKA pathway, and an ex novo enzyme synthesis.
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Affiliation(s)
- Nathalie Pizzinat
- Institut National de la Santé et de la Recherche Médicale U388, Institut Louis Bugnard, Centre Hospitalier Universitaire Rangueil, 31403 Toulouse Cedex 04, France
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27
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Parent MB, Master S, Kashlub S, Baker GB. Effects of the antidepressant/antipanic drug phenelzine and its putative metabolite phenylethylidenehydrazine on extracellular gamma-aminobutyric acid levels in the striatum. Biochem Pharmacol 2002; 63:57-64. [PMID: 11754874 DOI: 10.1016/s0006-2952(01)00856-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Phenelzine (PLZ) is a non-selective monoamine oxidase inhibitor (MAOI) commonly used to treat depression and panic disorder. As expected, PLZ increases brain levels of dopamine, norepinephrine, and serotonin. Interestingly, PLZ also elevates brain levels of gamma-aminobutyric acid (GABA), and previous studies have suggested that these increases may also contribute to the anxiolytic effects of PLZ. Using in vivo microdialysis in conscious, freely moving rats, combined with high performance liquid chromatography, the present experiments determined that PLZ (15 or 30 mg/kg, free base weight) increases extracellular levels of GABA in the caudate-putamen and nucleus accumbens. The results also indicated that phenylethylidenehydrazine (PEH; 29.6 mg/kg, free base weight), a putative intermediate metabolite of PLZ that is not an MAOI, also significantly increases extracellular GABA levels in the caudate-putamen. These findings provide further evidence that GABA may play an important role in the actions of PLZ and suggest that PEH should be pursued further as a GABAergic drug in its own right.
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Affiliation(s)
- Marise B Parent
- Department of Psychology, University of Alberta, Edmonton, Canada.
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28
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Lee MH, Lin RD, Shen LY, Yang LL, Yen KY, Hou WC. Monoamine oxidase B and free radical scavenging activities of natural flavonoids in Melastoma candidum D. Don. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2001; 49:5551-5555. [PMID: 11714358 DOI: 10.1021/jf010622j] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Monoamine oxidase type B (MAO-B) activity and free radicals are elevated in certain neurological diseases. Four natural flavonoids, quercitrin, isoquercitrin, rutin, and quercetin, were isolated for the first time from the leaves of Melastoma candidum D. Don. They exhibited an inhibitory effect on MAO-B. These potent flavonoids were purified using bioassay-guided fractionation and were separated by Diaion, Sephadex LH-20, and MCI CHP20P columns. The IC(50) values of the four potent flavonoids, quercitrin, isoquercitrin, rutin, and quercetin on monoamine oxidase were 19.06, 11.64, 3.89, and 10.89 microM and enzyme kinetics analysis revealed apparent inhibition constants (K(i)) of 21.01, 2.72, 1.83, and 7.95 microM, respectively, on the substrate, benzylamine. The four potent compounds also exhibited hydroxyl radical scavenging activity as determined using a spin trapping electron spin resonance method. This suggests that the four flavonoids from M. candidum possess both MAO-B inhibitory and free radical scavenging activities. These important properties may be used for preventing some neurodegenerative diseases in the future.
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Affiliation(s)
- M H Lee
- Graduate Institute of Pharmacognosy Science, Taipei Medical University, Taipei 110, Taiwan.
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29
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Tanay VA, Parent MB, Wong JT, Paslawski T, Martin IL, Baker GB. Effects of the antidepressant/antipanic drug phenelzine on alanine and alanine transaminase in rat brain. Cell Mol Neurobiol 2001; 21:325-39. [PMID: 11775064 DOI: 10.1023/a:1012697904299] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
1. Phenelzine (PLZ) is an antidepressant with anxiolytic properties. Acute and chronic PLZ administration increase brain GABA levels, an effect due, at least in part, to an inhibition of the activity of the GABA metabolizing enzyme, GABA transaminase (GABA-T). 2. Previous preliminary reports have indicated that acute PLZ treatment also elevates brain alanine levels. As with GABA, the metabolism of alanine involves a pyridoxal phosphate-dependent transaminase. 3. In the study reported here, the effects of acute PLZ treatment on the levels of various amino acids, some of which are also metabolized by pyridoxal phosphate-dependent transaminases were compared in rat whole brain. Of the 6 amino acids investigated, only GABA and alanine levels were elevated (in a time- and dose-dependent manner). 4. The elevation in brain alanine levels could be explained, at least in part, by a time- and dose-dependent inhibitory effect of PLZ on alanine transaminase (ALA-T), although as with GABA the increases are higher than expected from the degree of enzyme inhibition produced. In addition, we also showed that the elevation in alanine levels and the inhibition of alanine transaminase in the brain are retained after 14 days of PLZ treatment, and that PLZ produces a marked increase in extracellular levels of alanine. 5. These results are discussed in terms of their relevance to synaptic function and to the pharmacological profile of PLZ.
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Affiliation(s)
- V A Tanay
- Department of Psychiatry, University of Alberta, Edmonton, Canada
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30
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Chen Z, Wu J, Baker GB, Parent M, Dovichi NJ. Application of capillary electrophoresis with laser-induced fluorescence detection to the determination of biogenic amines and amino acids in brain microdialysate and homogenate samples. J Chromatogr A 2001; 914:293-8. [PMID: 11358224 DOI: 10.1016/s0021-9673(01)00539-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A procedure is described to derivatize 16 primary-amine-containing biogenic amines and amino acids in brain mixtures with the fluorogenic reagent 5-furoylquinoline-3-carboxaldehyde (FQ). These FQ-tagged compounds in the brain sample were resolved in less than 16 min based on micellar electrokinetic chromatography and laser-induced fluorescence. There was a linear relationship between the concentration of analyte and the fluorescence intensity, with correlation coefficients in the range of 0.96-1.00. The utility of this method for the quantification of the important inhibitory neurotransmitter gamma-aminobutyric acid in microdialysates and brain homogenates from rats is illustrated.
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Affiliation(s)
- Z Chen
- Department of Chemistry, University of Alberta, Edmonton, Canada
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31
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Paslawski T, Knaus E, Iqbal N, Coutts R, Baker G. ?-phenylethylidenehydrazine, a novel inhibitor of GABA transaminase. Drug Dev Res 2001. [DOI: 10.1002/ddr.1202] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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