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Zetterström TSC, Quansah E, Grootveld M. Effects of Methylphenidate on the Dopamine Transporter and Beyond. Curr Top Behav Neurosci 2022; 57:127-157. [PMID: 35507284 DOI: 10.1007/7854_2022_333] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The dopamine transporter (DAT) is the main target of methylphenidate (MPH), which remains the number one drug prescribed worldwide for the treatment of Attention-Deficit Hyperactivity Disorder (ADHD). In addition, abnormalities of the DAT have been widely associated with ADHD. Based on clinical and preclinical studies, the direction of DAT abnormalities in ADHD are, however, still unclear. Moreover, chronic treatment of MPH has been shown to increase brain DAT expression in both animals and ADHD patients, suggesting that findings of overexpressed levels of DAT in ADHD patients are possibly attributable to the effects of long-term MPH treatment rather than the pathology of the condition itself. In this chapter, we will discuss some of the effects exerted by MPH, which are related to its actions on catecholamine protein targets and brain metabolites, together with genes and proteins mediating neuronal plasticity. For this purpose, we present data from biochemical, proton nuclear magnetic resonance spectroscopy (1H-NMR) and gene/protein expression studies. Overall, results of the studies discussed in this chapter show that MPH has a complex biological/pharmacological action well beyond the DAT.
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Affiliation(s)
- Tyra S C Zetterström
- Pharmacology and Neuroscience Research Group, Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, Leicester, UK.
| | - Emmanuel Quansah
- Pharmacology and Neuroscience Research Group, Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, Leicester, UK
| | - Martin Grootveld
- Pharmacology and Neuroscience Research Group, Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, Leicester, UK
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Liebenberg N, Jensen E, Larsen ER, Kousholt BS, Pereira VS, Fischer CW, Wegener G. A Preclinical Study of Casein Glycomacropeptide as a Dietary Intervention for Acute Mania. Int J Neuropsychopharmacol 2018; 21:473-484. [PMID: 29726996 PMCID: PMC5932479 DOI: 10.1093/ijnp/pyy012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Accepted: 02/06/2018] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Casein glycomacropeptide is a peptide that lacks phenylalanine, tyrosine, and tryptophan. This profile may enable it to deplete phenylalanine, tyrosine, and tryptophan, and subsequently the synthesis of dopamine and serotonin in the brain. Dopamine- and serotonin-depleting amino acid mixtures have shown promise as acute antimanic treatments. In this study, we explore the depleting effects on amino acids, dopamine and serotonin as well as its actions on manic-like and other behavior in rats. METHODS Casein glycomacropeptide and a selection of amino acid mixtures were administered orally at 2, 4, or 8 h or for 1 week chronically. Amino acid and monoamine levels were measured in plasma and brain and behavior was assessed in the amphetamine-hyperlocomotion, forced swim, prepulse inhibition, and elevated plus maze tests. RESULTS Casein glycomacropeptide induced a time-dependent reduction in tyrosine, tryptophan, and phenylalanine in brain and plasma which was augmented by supplementing with leucine. Casein glycomacropeptide +leucine reduced dopamine in the frontal cortex and serotonin in the hippocampus, frontal cortex, and striatum after 2 and 4 h. Casein glycomacropeptide+leucine also had antimanic activity in the amphetamine-induced hyperlocomotion test at 2 h after a single acute treatment and after 1 week of chronic treatment. CONCLUSIONS Casein glycomacropeptide-based treatments and a branched-chain amino acid mixture affected total tissue levels of dopamine in the frontal cortex and striatum and serotonin in the frontal cortex, striatum, and hippocampus of rats in a time-dependent fashion and displayed antimanic efficacy in a behavioral assay of mania.
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Affiliation(s)
- Nico Liebenberg
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Denmark
| | | | - Erik Roj Larsen
- Department Psychiatry Odense, Psychiatry in the Region of Southern Denmark, Denmark,Department of Psychiatry, Institute for Clinical Research, University of Southern Denmark, Denmark
| | - Birgitte Saima Kousholt
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark,Department of Clinical Medicine, AUGUST Centre, Aarhus University, Risskov, Denmark
| | - Vitor Silva Pereira
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Denmark
| | - Christina Weide Fischer
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Denmark
| | - Gregers Wegener
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Denmark,Department of Clinical Medicine, AUGUST Centre, Aarhus University, Risskov, Denmark,Centre for Pharmaceutical Excellence, School of Pharmacy, North-West University, South Africa,Correspondence: Gregers Wegener, Translational Neuropsychiatry Unit, Aarhus University Hospital, Skovagervej 2, 8240 Risskov, Denmark ()
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Quansah E, Ruiz-Rodado V, Grootveld M, Probert F, Zetterström TSC. 1H NMR-based metabolomics reveals neurochemical alterations in the brain of adolescent rats following acute methylphenidate administration. Neurochem Int 2017; 108:109-120. [PMID: 28268188 DOI: 10.1016/j.neuint.2017.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/12/2017] [Accepted: 03/03/2017] [Indexed: 12/22/2022]
Abstract
The psychostimulant methylphenidate (MPH) is increasingly used in the treatment of attention deficit hyperactivity disorder (ADHD). While there is little evidence for common brain pathology in ADHD, some studies suggest a right hemisphere dysfunction among people diagnosed with the condition. However, in spite of the high usage of MPH in children and adolescents, its mechanism of action is poorly understood. Given that MPH blocks the neuronal transporters for dopamine and noradrenaline, most research into the effects of MPH on the brain has largely focused on these two monoamine neurotransmitter systems. Interestingly, recent studies have demonstrated metabolic changes in the brain of ADHD patients, but the impact of MPH on endogenous brain metabolites remains unclear. In this study, a proton nuclear magnetic resonance (1H NMR)-based metabolomics approach was employed to investigate the effects of MPH on brain biomolecules. Adolescent male Sprague Dawley rats were injected intraperitoneally with MPH (5.0 mg/kg) or saline (1.0 ml/kg), and cerebral extracts from the left and right hemispheres were analysed. A total of 22 variables (representing 13 distinct metabolites) were significantly increased in the MPH-treated samples relative to the saline-treated controls. The upregulated metabolites included: amino acid neurotransmitters such as GABA, glutamate and aspartate; large neutral amino acids (LNAA), including the aromatic amino acids (AAA) tyrosine and phenylalanine, both of which are involved in the metabolism of dopamine and noradrenaline; and metabolites associated with energy and cell membrane dynamics, such as creatine and myo-inositol. No significant differences in metabolite concentrations were found between the left and right cerebral hemispheres. These findings provide new insights into the mechanisms of action of the anti-ADHD drug MPH.
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Affiliation(s)
- Emmanuel Quansah
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester LE1 9BH, UK
| | - Victor Ruiz-Rodado
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester LE1 9BH, UK
| | - Martin Grootveld
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester LE1 9BH, UK
| | - Fay Probert
- Department of Pharmacology, Oxford University, Mansfield Road, Oxford OX1 3QT, UK
| | - Tyra S C Zetterström
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester LE1 9BH, UK.
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Le Masurier M, Zetterström T, Cowen P, Sharp T. Tyrosine-free amino acid mixtures reduce physiologically-evoked release of dopamine in a selective and activity-dependent manner. J Psychopharmacol 2014; 28:561-9. [PMID: 24108408 DOI: 10.1177/0269881113507642] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Depletion of the catecholamine precursor tyrosine using tyrosine-free amino acid mixtures is an important tool in neuropsychological studies, and often considered dopamine selective on the basis of neuropharmacological studies. However, little is known of the effects of tyrosine depletion when catecholamine neurons are activated physiologically. Here we investigated the effect of tyrosine-free amino acid mixtures on catecholamine release evoked in vivo using a stimulation paradigm aimed to approximate the phasic firing pattern of these neurons that accompanies cognitive and behavioural change. Dopamine and noradrenaline release was monitored by microdialysis in rat medial prefrontal cortex (mPFC) and striatum (chloral hydrate anaesthesia, perfusion medium containing 1 µM cocaine). Electrical stimulation of the medial forebrain bundle (MFB) caused a short-lasting, frequency-dependent increase in dopamine and noradrenaline. A full tyrosine-free amino acid mixture reduced the release of dopamine in mPFC and striatum, across a range of stimulation frequencies, and the effect was greater as stimulation frequency increased. Similar results were obtained using a smaller tyrosine-free amino acid mixture. In the same experiments showing decreased dopamine, neither tyrosine-free mixture of amino acids significantly altered stimulation-evoked release of noradrenaline. These results show that tyrosine depletion using tyrosine-free amino acid mixtures causes a selective, activity-dependent decrease in dopamine release when dopamine neurons are driven physiologically.
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Affiliation(s)
| | | | - Philip Cowen
- Department of Psychiatry, Warneford Hospital, Oxford, UK
| | - Trevor Sharp
- Department of Pharmacology, University of Oxford, Oxford, UK
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Bjork JM, Grant SJ, Chen G, Hommer DW. Dietary tyrosine/phenylalanine depletion effects on behavioral and brain signatures of human motivational processing. Neuropsychopharmacology 2014; 39:595-604. [PMID: 23995581 PMCID: PMC3895237 DOI: 10.1038/npp.2013.232] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 08/26/2013] [Accepted: 08/27/2013] [Indexed: 11/09/2022]
Abstract
Dopamine (DA) neurotransmission is critical for motivational processing. We assessed whether disruption of DA synthesis in healthy controls using an amino-acid beverage devoid of catecholamine precursors (tyrosine-phenylalanine depletion (TPD)) would blunt recruitment of the nucleus accumbens (NAcc) by rewards. Sixteen controls ingested each of a tyr/phe-depleting beverage (DEP) or a tyr/phe-balanced (BAL) control beverage in two laboratory visits. Five hours after consumption of each drink, subjects underwent functional magnetic resonance imaging while they viewed anticipatory cues to respond to a target to either win money or avoid losing money. TPD did not exert main effects on mood or on task behavior, but affected brain activation. In right NAcc, TPD blunted activation by anticipation of high rewards. In left NAcc, recruitment anticipating high rewards was modulated by individual differences in mood change across the DEP drink day, where subjects whose mood worsened following TPD (relative to within-day mood change under BAL conditions) also showed lower activation under DEP conditions relative to BAL conditions. Exploratory analysis indicated that TPD qualitatively blunted the voxel-wise spatial extent of suprathreshold activation by reward anticipation. Finally, loss outcomes activated anterior insula under DEP conditions but not under BAL conditions. These data indicate that: (1) dietary depletion of catacholamine precursors will blunt dopaminergic mesolimbic activity, and (2) in controls, synthetic pathways of this neurocircuitry maintain sufficient buffering capacity to resist an effect on motivated behavior. Additional studies are needed to determine if clinical populations would show similar resistance to behavioral effects of TPD.
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Affiliation(s)
- James M Bjork
- Division of Clinical Neuroscience and Behavioral Research, National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD, USA,Division of Clinical Neuroscience and Behavioral Research, National Institute on Drug Abuse, National Institutes of Health, 6001 Executive Boulevard, Room 3163, Bethesda, MD 20892, USA, Tel: +1 301 443 3209, Fax: +1 301 443 6814, E-mail:
| | - Steven J Grant
- Division of Clinical Neuroscience and Behavioral Research, National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD, USA
| | - Gang Chen
- Scientific and Statistical Computing Core, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Daniel W Hommer
- Laboratory of Clinical and Translational Studies, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
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Leung S, Croft RJ, Guille V, Scholes K, O'Neill BV, Phan KL, Nathan PJ. Acute dopamine and/or serotonin depletion does not modulate mismatch negativity (MMN) in healthy human participants. Psychopharmacology (Berl) 2010; 208:233-44. [PMID: 20012022 DOI: 10.1007/s00213-009-1723-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Accepted: 11/02/2009] [Indexed: 01/08/2023]
Abstract
RATIONALE Schizophrenia is commonly associated with impairments in pre-attentive change detection, as represented by reduced mismatch negativity (MMN). While the neurochemical basis of MMN has been linked to N-methyl-D: -aspartic acid (NMDA) receptor function, the roles of the dopaminergic and/or the serotonergic systems are not fully explored in humans. OBJECTIVES The aim of the present study was to investigate the effects of acutely depleting dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) alone or simultaneously by depleting their amino acid precursors on MMN in healthy participants. METHODS Sixteen healthy male subjects participated in a double-blind, placebo-controlled, cross-over design in which each subject's duration MMN was assessed under four acute treatment conditions separated by a 5-day washout period: balanced amino acid control (no depletion), tyrosine/phenylalanine depletion (to reduce DA neurotransmission), tryptophan depletion (to reduce 5-HT neurotransmission) and tryptophan/tyrosine/phenylalanine depletion (to reduce DA and 5-HT neurotransmission simultaneously). RESULTS Acute depletion of either DA and 5-HT alone or simultaneously had no effect on MMN. CONCLUSIONS These findings suggest that modulation of the dopaminergic and serotonergic systems acutely does not lead to changes in MMN.
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Affiliation(s)
- Sumie Leung
- Brain Sciences Institute, Faculty of Life and Social Sciences, Swinburne University of Technology, P.O. Box 218, John Street Hawthorn, 3122, Melbourne, VIC, Australia.
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Mann C, Croft RJ, Scholes KE, Dunne A, O'Neill BV, Leung S, Copolov D, Phan KL, Nathan PJ. Differential effects of acute serotonin and dopamine depletion on prepulse inhibition and p50 suppression measures of sensorimotor and sensory gating in humans. Neuropsychopharmacology 2008; 33:1653-66. [PMID: 17895917 DOI: 10.1038/sj.npp.1301556] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Schizophrenia is associated with impairments of sensorimotor and sensory gating as measured by prepulse inhibition (PPI) of the acoustic startle response and P50 suppression of the auditory event-related potential respectively. While serotonin and dopamine play an important role in the pathophysiology and treatment of schizophrenia, their role in modulating PPI and P50 suppression in humans is yet to be fully clarified. To further explore the role of serotonin and dopamine in PPI and P50 suppression, we examined the effects of acute tryptophan depletion (to decrease serotonin) and acute tyrosine/phenylalanine depletion (to decrease dopamine) on PPI and P50 suppression in healthy human participants. In addition, we also examined for the first time, the effects of simultaneous serotonin and dopamine depletion (ie combined monoamine depletion) on PPI and P50 suppression. The study was a double-blind, placebo-controlled cross-over design in which 16 healthy male participants completed the PPI and P50 paradigms under four acute treatment conditions: (a) balanced/placebo control, (b) acute tryptophan depletion, (c) acute tyrosine/phenylalanine depletion, and (d) acute tyrosine/phenylalanine/tryptophan depletion (combined monoamine depletion). Selective depletion of dopamine had no significant effect on either PPI or P50 suppression, whereas selective serotonin depletion significantly disrupted PPI, but not P50 suppression. Finally, the simultaneous depletion of both serotonin and dopamine resulted in significant reduction of both PPI and P50 suppression. We suggest these results can be explained by theories relating to optimal levels of monoaminergic neurotransmission and synergistic interactions between serotonergic and dopaminergic systems for normal 'gating' function. These findings suggest that a dysfunction in both serotonin and dopamine neurotransmission may, in part, be responsible for the gating deficits observed in schizophrenia, and their normalization following administration of atypical antipsychotic drugs.
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Affiliation(s)
- Collette Mann
- Behavioural Neuroscience Laboratory, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Melbourne, VIC, Australia
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8
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Preece MA, Sibson NR, Raley JM, Blamire A, Styles P, Sharp T. Region-specific effects of a tyrosine-free amino acid mixture on amphetamine-induced changes in BOLD fMRI signal in the rat brain. Synapse 2007; 61:925-32. [PMID: 17701967 DOI: 10.1002/syn.20442] [Citation(s) in RCA: 15] [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
BACKGROUND Acute depletion of tyrosine using a tyrosine-free amino acid mixture offers a novel dietary approach to inhibit activated dopamine pathways in the brain. This study investigated the potential of in vivo functional magnetic resonance imaging (fMRI) methods as a noninvasive means to detect effects of tyrosine depletion on dopamine function. METHODS Changes in blood-oxgenation level dependent (BOLD) contrast induced by administration of the dopamine-releasing agent, amphetamine (3 mg/kg i.v.), were measured in halothane-anaesthetised rats. RESULTS Amphetamine evoked changes in BOLD signal intensity with the greatest effects observed in the nucleus accumbens (-7.7%), prefrontal cortex (-13.6%), and motor cortex (+12.5%). Pretreatment with a tyrosine-free amino acid mixture attenuated the response to amphetamine in some regions (nucleus accumbens and prefrontal cortex), but not others (motor cortex). Amphetamine itself had no effect in thalamus and hippocampus but, surprisingly, increased the BOLD signal after the amino acid mixture. CONCLUSION These experiments demonstrate that amphetamine evokes region-specific changes in the BOLD signal in rats, and that this effect is attenuated in some but not all regions by tyrosine depletion. The data support the application of fMRI techniques for studying the effects of tyrosine depletion on dopamine function in animals and also humans.
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Affiliation(s)
- Mark A Preece
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
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Scholes KE, Harrison BJ, O'Neill BV, Leung S, Croft RJ, Pipingas A, Phan KL, Nathan PJ. Acute serotonin and dopamine depletion improves attentional control: findings from the stroop task. Neuropsychopharmacology 2007; 32:1600-10. [PMID: 17151596 DOI: 10.1038/sj.npp.1301262] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Schizophrenia is associated with impairments of attentional control on classic experimental paradigms such as the Stroop task. However, at a basic level the neurochemical mechanisms that may be responsible for such impairments are poorly understood. In this study, we sought to investigate the influence of brain monoamine function on Stroop task performance in healthy participants using the established methods of acute dietary serotonin, dopamine, and combined monoamine depletion. The study was a double-blind placebo controlled design in which 12 healthy male participants completed the Stroop task under four acute treatment conditions: (a) balanced/placebo control, (b) acute tryptophan depletion, (c) acute tyrosine/phenylalanine depletion, and (d) acute tyrosine/phenylalanine/tryptophan depletion (combined monoamine depletion). Decreased Stroop interference indicating improved attentional control was observed after both tryptophan depletion and tyrosine/phenylalanine depletion, while there was no significant change in interference after combined monoamine depletion. Findings suggest that reduced tonic dopamine or serotonin activity within specific neural circuits (such as the striatum, anterior cingulate, or prefrontal cortex) may play a critical role in attentional control, possibly by improving gating of information via reducing noise in monoaminergic systems. These findings enhance our understanding of the neurochemical basis of attentional control and the possible cause of attentional control deficits in schizophrenia.
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Affiliation(s)
- Kirsty E Scholes
- Behavioural Neuroscience Laboratory, Department of Physiology, Monash Centre for Brain and Behavior, Monash University, Melbourne, VIC, Australia
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Fernstrom JD, Fernstrom MH. Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. J Nutr 2007; 137:1539S-1547S; discussion 1548S. [PMID: 17513421 DOI: 10.1093/jn/137.6.1539s] [Citation(s) in RCA: 394] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Aromatic amino acids in the brain function as precursors for the monoamine neurotransmitters serotonin (substrate tryptophan) and the catecholamines [dopamine, norepinephrine, epinephrine; substrate tyrosine (Tyr)]. Unlike almost all other neurotransmitter biosynthetic pathways, the rates of synthesis of serotonin and catecholamines in the brain are sensitive to local substrate concentrations, particularly in the ranges normally found in vivo. As a consequence, physiologic factors that influence brain pools of these amino acids, notably diet, influence their rates of conversion to neurotransmitter products, with functional consequences. This review focuses on Tyr and phenylalanine (Phe). Elevating brain Tyr concentrations stimulates catecholamine production, an effect exclusive to actively firing neurons. Increasing the amount of protein ingested, acutely (single meal) or chronically (intake over several days), raises brain Tyr concentrations and stimulates catecholamine synthesis. Phe, like Tyr, is a substrate for Tyr hydroxylase, the enzyme catalyzing the rate-limiting step in catecholamine synthesis. Tyr is the preferred substrate; consequently, unless Tyr concentrations are abnormally low, variations in Phe concentration do not affect catecholamine synthesis. Unlike Tyr, Phe does not demonstrate substrate inhibition. Hence, high concentrations of Phe do not inhibit catecholamine synthesis and probably are not responsible for the low production of catecholamines in subjects with phenylketonuria. Whereas neuronal catecholamine release varies directly with Tyr-induced changes in catecholamine synthesis, and brain functions linked pharmacologically to catecholamine neurons are predictably altered, the physiologic functions that utilize the link between Tyr supply and catecholamine synthesis/release are presently unknown. An attractive candidate is the passive monitoring of protein intake to influence protein-seeking behavior.
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Affiliation(s)
- John D Fernstrom
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
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Vrshek-Schallhorn S, Wahlstrom D, Benolkin K, White T, Luciana M. Affective bias and response modulation following tyrosine depletion in healthy adults. Neuropsychopharmacology 2006; 31:2523-36. [PMID: 16880769 DOI: 10.1038/sj.npp.1301172] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Acute phenylalanine/tyrosine depletion (ATPD) has been used to transiently lower central nervous system dopamine activity in animals and humans. Findings suggest that ATPD may impact dopamine transmission in limbic and striatal regions. Impact on cognitive functions has varied across studies, although several recent reports suggest that affective processing in the context of a go/no-go response control task may be impaired during ATPD. In this study, response control under affective vs nonaffective conditions was examined in healthy individuals who underwent either ATPD or a balanced condition in a between-subjects design. Effects of ATPD were validated through its effects on serum prolactin secretion. ATPD resulted in significantly increased prolactin levels relative to the balanced mixture. Although there were no differences in self-reported mood between the groups, individuals in the ATPD condition demonstrated diminished sensitivity to positively valenced words and seemingly enhanced sensitivity to negatively valenced words in an affective go/no-go task. They also showed difficulties in modulating ongoing behavior in a nonaffective go/no-go task when responses had to be intermittently inhibited then immediately restarted. Basic motor functions were not impacted. Findings are discussed in relation to dopamine's role in switching signals within neural networks that are important for response modulation and affective control.
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Lange KW, Mecklinger L, Walitza S, Becker G, Gerlach M, Naumann M, Tucha O. Brain dopamine and kinematics of graphomotor functions. Hum Mov Sci 2006; 25:492-509. [PMID: 16859791 DOI: 10.1016/j.humov.2006.05.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Three experiments were performed in an attempt to achieve a better understanding of the effect of dopamine on handwriting. In the first experiment, kinematic aspects of handwriting movements were compared between healthy participants and patients with Parkinson's disease (PD) on their usual dopaminergic treatment and following withdrawal of dopaminergic medication. In the second experiment, the writing performance of healthy participants with a hyperechogenicity of the substantia nigra as detected by transcranial sonography (TCS) was compared with the performance of healthy participants with low echogenicity of the substantia nigra. The third experiment examined the effect of central dopamine reduction on kinematic aspects of handwriting movements in healthy adults using acute phenylalanine and tyrosine depletion (APTD). A digitising tablet was used for the assessment of handwriting movements. Participants were asked to perform a simple writing task. Movement time, distance, velocity, acceleration and measures of fluency of handwriting movements were measured. The kinematic analysis of handwriting movements revealed that alterations of central dopaminergic neurotransmission adversely affect movement execution during handwriting. In comparison to the automatic processing of handwriting movements displayed by control participants, participants with an altered dopaminergic neurotransmission shifted from an automatic to a controlled processing of movement execution. Central dopamine appears to be of particular importance with regard to the automatic execution of well-learned movements.
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Affiliation(s)
- Klaus W Lange
- Department of Experimental Psychology, University of Regensburg, 93040 Regensburg, Germany.
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13
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Casey KF, Benkelfat C, Young SN, Leyton M. Lack of effect of acute dopamine precursor depletion in nicotine-dependent smokers. Eur Neuropsychopharmacol 2006; 16:512-20. [PMID: 16545549 DOI: 10.1016/j.euroneuro.2006.02.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 01/26/2006] [Accepted: 02/02/2006] [Indexed: 11/18/2022]
Abstract
RATIONALE Nicotine increases dopamine (DA) release but its role in nicotine dependence remains unclear. OBJECTIVE To assess the role of DA in nicotine craving and self-administration using acute phenylalanine/tyrosine depletion (APTD). METHODS Fifteen nicotine-dependent men ingested, a minimum of 3days apart, a nutritionally balanced amino acid (AA) mixture (BAL), a mixture deficient in the catecholamine precursors, phenylalanine and tyrosine, and APTD followed by the immediate DA precursor, L-DOPA. Beginning 3h after ingestion of the AA mixture, subjects smoked 4 cigarettes. Craving, mood, and other aspects of subjective state were assessed with self-report scales. Smoking puff topography was measured with a computerized flowmeter. RESULTS APTD did not change smoking puff topography, cigarette craving, or subjective effects of smoking. CONCLUSIONS The findings suggest that in nicotine-dependent smokers craving for cigarettes, subjective effects of nicotine, and the self-administration of freely available cigarettes are largely unrelated to acute changes in DA neurotransmission.
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Affiliation(s)
- Kevin F Casey
- Department of Psychiatry, McGill University, 1033 Pine Avenue West, Montreal, Quebec, Canada H3A 1A1
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14
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Leyton M, Casey KF, Delaney JS, Kolivakis T, Benkelfat C. Cocaine craving, euphoria, and self-administration: a preliminary study of the effect of catecholamine precursor depletion. Behav Neurosci 2006; 119:1619-27. [PMID: 16420164 DOI: 10.1037/0735-7044.119.6.1619] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The authors used the acute phenylalanine-tyrosine depletion (APTD) method to test the effect of transient catecholamine precursor depletion on cocaine craving, euphoria, and self-administration. Eight nondependent, nontreatment-seeking cocaine users self-administered 3 doses of cocaine (0.6, 1.5, 3.0 mg/kg, taken intranasally) following ingestion of (a) a nutritionally balanced amino acid mixture, (b) APTD, and (c) APTD followed by L-dopa/carbidopa (2x100 mg/25 mg). APTD decreased both cue and cocaine-induced drug craving but not euphoria or self-administration. APTD+L-dopa also decreased drug craving, possibly reflecting the ability of L-dopa to transiently decrease dopamine cell firing. Together, these preliminary results suggest that the craving elicited by cocaine and cocaine cues is related to changes in catecholamine neurotransmission. Euphoria and the self-administration of freely available drugs by regular users, in comparison, might be better accounted for by other mechanisms.
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Affiliation(s)
- Marco Leyton
- McGill University, Department of Psychiatry, Montreal, PQ, Canada.
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Le Masurier M, Oldenzeil W, Lehman C, Cowen P, Sharp T. Effect of acute tyrosine depletion in using a branched chain amino-acid mixture on dopamine neurotransmission in the rat brain. Neuropsychopharmacology 2006; 31:310-7. [PMID: 16034439 DOI: 10.1038/sj.npp.1300835] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Central dopamine function is reduced by decreasing the availability of the catecholamine precursor, tyrosine, using a tyrosine-free amino acid mixture containing multiple large neutral as well as branched chain amino-acids, which compete with tyrosine for uptake into the brain. Current mixtures are cumbersome to make and administer, and unpalatable to patients and volunteers. Here, we investigate whether individual or limited amino-acid combinations could reduce brain tyrosine levels and hence dopamine function. Measurements of regional brain tyrosine levels, catecholamine and indoleamine synthesis (L-DOPA and 5-HTP accumulation, respectively) were used to identify an effective paradigm to test in neurochemical, behavioral and fos immunocytochemical models. Administration of leucine or isoleucine, or a mixture of leucine, isoleucine, and valine reduced tyrosine and 5-HTP, but not L-DOPA accumulation. A mixture of leucine, valine, and isoleucine supplemented with tryptophan reduced brain tyrosine and L-DOPA, but not 5-HTP. In microdialysis experiments this amino-acid mixture reduced basal and amphetamine-evoked striatal dopamine release, as well as amphetamine-induced hyperactivity. This mixture also reduced amphetamine-induced fos expression in striatal areas. In conclusion, the present study identified a small combination of amino acids that reduces brain tyrosine and dopamine function in a manner similar to mixtures of multiple amino acids. This minimal mixture may have use as a dopamine reducing paradigm in patient and volunteer studies.
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Mehta MA, Gumaste D, Montgomery AJ, McTavish SFB, Grasby PM. The effects of acute tyrosine and phenylalanine depletion on spatial working memory and planning in healthy volunteers are predicted by changes in striatal dopamine levels. Psychopharmacology (Berl) 2005; 180:654-63. [PMID: 16163534 DOI: 10.1007/s00213-004-2128-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Accepted: 12/02/2004] [Indexed: 11/30/2022]
Abstract
RATIONALE Dopamine (DA) is considered important in the modulation of tasks of spatial working memory. However, the findings from studies in humans to date are mixed. While this may be due to the characteristics of the tasks used, it is also possible that these findings are explained by variable central effects of the manipulations used. OBJECTIVE To test the effects of acute tyrosine and phenylalanine depletion (TPD, which reduces synthesis and release of brain DA) on cognitive function and relate changes in performance accuracy to the central effects of TPD measured with [11C]raclopride positron emission tomography (PET). METHODS Fourteen participants were given tests of spatial working memory, planning, verbal memory span and trial-and-error learning after acute TPD, seven of whom also received PET scans to measure changes in striatal DA levels. RESULTS Although TPD produced a clear reduction in tyrosine and phenylalanine availability to the brain, no impairments on any of the cognitive tests were observed. However, changes in spatial working memory and planning accuracy after TPD showed a highly significant relationship with the changes in striatal DA levels. CONCLUSIONS Our findings suggest that the effects of TPD on spatial working memory and planning may be unreliable due to the variability of the changes in brain DA levels achieved with this manipulation.
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Affiliation(s)
- Mitul A Mehta
- PET Psychiatry, Cyclotron Building, MRC Clinical Sciences Centre, Imperial College, Hammersmith Hospital, London, W12 0NN, UK.
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Harrison BJ, Olver JS, Norman TR, Burrows GD, Wesnes KA, Nathan PJ. Selective effects of acute serotonin and catecholamine depletion on memory in healthy women. J Psychopharmacol 2004; 18:32-40. [PMID: 15107182 DOI: 10.1177/0269881104040225] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
There is converging evidence that brain serotonin and dopamine may selectively modulate learning and memory in humans. However, this has not been directly demonstrated. In the current study, we used the method of amino acid precursor depletion to explore the effects of low serotonin and catecholamine function on memory in healthy female volunteers. Participants completed three experimental sessions: (i) tryptophan depletion (TD to lower 5-HT); (ii) tyrosine and phenylalanine depletion (TPD to lower catecholamines); and (iii) a balanced control condition (Bal). All testing was conducted in a double-blind, placebo-controlled, crossover design. Cognitive and mood assessments were performed at baseline and 5 h after ingesting the amino acid mixture. Consistent with previous studies, TD impaired declarative memory consolidation on a structured word-learning task, while TPD, acting to lower brain dopamine availability, impaired spatial working memory. No secondary deficits were observed on measures of attention, short-term memory or subjective mood state. These findings suggest that low brain serotonin versus dopamine selectively impairs memory performance in humans. This may shed light on the role of these neurotransmitters in disorders that are characterized by significant memory impairment.
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Affiliation(s)
- Ben J Harrison
- Neuropsychopharmacology Laboratory, Brain Sciences Institute, Swinburne University of Technology, Melbourne Australia
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Abstract
A number of techniques temporarily lower the functioning of monoamines: acute tryptophan depletion (ATD), alpha-methyl-para-tyrosine (AMPT) and acute phenylalanine/tyrosine depletion (APTD). This paper reviews the results of monoamine depletion studies in humans for the period 1966 until December 2002. The evidence suggests that all three interventions are specific, in terms of their short-term effects on one or two neurotransmitter systems, rather than on brain protein metabolism in general. The AMPT procedure is somewhat less specific, affecting both the dopamine and norepinephrine systems. The behavioral effects of ATD and AMPT are remarkably similar. Neither procedure has an immediate effect on the symptoms of depressed patients; however, both induce transient depressive symptoms in some remitted depressed patients. The magnitude of the effects, response rate and quality of response are also comparable. APTD has not been studied in recovered major depressive patients. Despite the similarities, the effects are distinctive in that ATD affects a subgroup of recently remitted patients treated with serotonergic medications, whereas AMPT affects recently remitted patients treated with noradrenergic medications. The evidence also suggests that ATD and APTD affect different cognitive functions, in particular different memory systems. Few studies investigated cognitive effects of the procedures in patients. Patients who are in remission for longer may also be vulnerable to ATD and AMPT, but the relationship with prior treatment is much weaker. For these patients, individual vulnerability markers are the more important determinants of depressive response, making these techniques potentially useful models of vulnerability to depression.
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Affiliation(s)
- L Booij
- Department of Psychology, Leiden University, Leiden 2333 AK, The Netherlands.
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Le Masurier M, Houston G, Cowen P, Grasby P, Sharp T, Hume S. Tyrosine-free amino acid mixture attenuates amphetamine-induced displacement of [11C]raclopride in striatum in vivo: A rat PET study. Synapse 2003; 51:151-7. [PMID: 14618682 DOI: 10.1002/syn.10285] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Previous neurochemical and behavioural studies show that tyrosine depletion using a nutritionally balanced tyrosine-free amino acid mixture attenuates the dopamine-releasing and psychostimulant properties of amphetamine. Here we investigate the effect of a tyrosine-free amino acid mixture on striatal binding of [(11)C]raclopride, and amphetamine-induced [(11)C]raclopride displacement, using positron emission tomography in the rat. Rats were scanned for 60 min after an i.v. injection of approximately 11 MBq [(11)C]raclopride using a quad-HIDAC system. Amphetamine (2 mg/kg i.p., 30 min prior to scan) caused a 12% reduction in [(11)C]raclopride distribution volume ratio (DVR) compared to saline-injected controls. The tyrosine-free amino acid mixture (1 g/kg i.p.) caused a small (+7%) but statistically insignificant increase in [(11)C]raclopride DVR and attenuated, although it did not fully block, the amphetamine-induced reduction. These data are in keeping with previous neurochemical, immunocytochemical, and behavioural studies showing that tyrosine-free amino acid mixtures reduce dopamine function and offer promise for future PET studies testing the effect of tyrosine-depleting paradigms on dopamine release in humans.
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Affiliation(s)
- Marisa Le Masurier
- University Department of Pharmacology, Mansfield Road, Oxford OX1 3QT, UK
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