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Abstract
INTRODUCTION Although there is clear evidence for the serotonergic regulation of descending control of pain in animals, little direct evidence exists in humans. The majority of our knowledge comes from the use of serotonin (5-HT)-modulating antidepressants as analgesics in the clinical management of chronic pain. OBJECTIVES Here, we have used an acute tryptophan depletion (ATD) to manipulate 5-HT function and examine its effects of ATD on heat pain threshold and tolerance, attentional manipulation of nociceptive processing and mood in human volunteers. METHODS Fifteen healthy participants received both ATD and balanced amino acid (BAL) drinks on two separate sessions in a double-blind cross-over design. Pain threshold and tolerance were determined 4 h post-drink via a heat thermode. Additional attention, distraction and temperature discrimination paradigms were completed using a laser-induced heat pain stimulus. Mood was assessed prior and throughout each session. RESULTS Our investigation reported that the ATD lowered plasma TRP levels by 65.05 ± 7.29% and significantly reduced pain threshold and tolerance in response to the heat thermode. There was a direct correlation between the reduction in total plasma TRP levels and reduction in thermode temperature. In contrast, ATD showed no effect on laser-induced pain nor significant impact of the distraction-induced analgesia on pain perception but did reduce performance of the painful temperature discrimination task. Importantly, all findings were independent of any effects of ATD on mood. CONCLUSION As far as we are aware, it is the first demonstration of 5-HT effects on pain perception which are not confounded by mood changes.
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Sadeghiyan-Rizi T, Fooladi J, Momhed Heravi M, Sadrai S. Optimization of L-Tryptophan Biosynthesis From L-Serine of Processed Iranian Beet and Cane Molasses and Indole by Induced Escherichia coli ATCC 11303 Cells. Jundishapur J Microbiol 2014; 7:e10589. [PMID: 25371801 PMCID: PMC4217663 DOI: 10.5812/jjm.10589] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 04/25/2013] [Accepted: 05/05/2013] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND L-tryptophan is an important ingredient in medicines, especially in neuromedicines such as antidepressants. Many commercial processes employ various microorganisms with high tryptophan synthase activity to produce L-tryptophan from indole and L-serine, but these processes are very costly due to the costs of precursors, especially L-serine. OBJECTIVES For this reason, we studied the ability to use processed Iranian cane and beet molasses as L-serine sources for L-tryptophan production, which enables us to reach a cost-effective process. MATERIALS AND METHODS Whole cells of Escherichia coli ATCC 11303 were induced for L-tryptophan synthase by addition of indole to the growth medium and bacterial cells harvested from the growth medium were used as biocatalysts in the production medium. Conditions of the production medium were optimized and Iranian cane and beet molasses were processed by solvent extraction with ethanol and n-butanol and used as L-serine sources of the production medium. Amount of L-tryptophan and theoretical yield of L-tryptophan production were determined by High Performance Liquid Chromatography and by a colorimetrical method on the basis of the remaining indole assay, respectively. RESULTS L-tryptophan production increased by 15 folds, when indole was used as an inducer. L-tryptophan was produced from processed Iranian beet molasses in satisfactory amounts (0.53 mM) and no exogenous pyridoxal phosphate was required as a cofactor under our experimental conditions. CONCLUSIONS The obtained results proved that Iranian beet molasses include significant amounts of L-serine that makes them a suitable substitution for L-serine. Findings of the present study give impetus to use of Iranian beet molasses for cost-effective L-Trp production in the amino acid industry.
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Affiliation(s)
- Tahereh Sadeghiyan-Rizi
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Isfahan University of Medical Sciences, Isfahan, IR Iran
| | - Jamshid Fooladi
- Department of Biology, National Laboratory of Industrial Microbiology, Faculty of Science, Alzahra University, Tehran, IR Iran
| | - Majid Momhed Heravi
- Department of Chemistry, Faculty of Science, Alzahra University, Tehran, IR Iran
| | - Sima Sadrai
- Department of Pharmaceutics, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, IR Iran
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The effect of acute tryptophan depletion on mood and impulsivity in polydrug ecstasy users. Psychopharmacology (Berl) 2014; 231:707-16. [PMID: 24142202 DOI: 10.1007/s00213-013-3287-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 09/07/2013] [Indexed: 12/19/2022]
Abstract
RATIONALE Several studies suggest users of 3,4-methylenedioxymethamphetamine (ecstasy) have low levels of serotonin. Low serotonin may make them susceptible to lowered mood. OBJECTIVE This work aims to study the acute effects on mood and impulsivity of lowering serotonin levels with acute tryptophan depletion in polydrug ecstasy users and to determine whether effects were different in men and women. METHODS In a double-blind cross-over study, participants who had used ecstasy at least 25 times (n = 13) and nonuser controls (n = 17) received a tryptophan-deficient amino acid mixture and a control amino acid mixture containing tryptophan, at least 1 week apart. Mood was measured using the profile of mood states, and impulsivity was measured with the Go/No-Go task. RESULTS The main result shows that a lowering of mood after acute tryptophan depletion occurred only in female polydrug ecstasy users (n = 7), relative to controls (n = 9). Results from the Go/No-Go task suggested that impulsivity was not increased by acute tryptophan depletion in polydrug ecstasy users. LIMITATION The group sizes were small, when males and females were considered separately. CONCLUSIONS Women polydrug ecstasy users appear to be more susceptible than men to the effects of lowered serotonin levels. If use of ecstasy alone or in conjunction with other drugs causes progressive damage of serotonin neurons, women polydrug ecstasy users may become susceptible to clinical depression.
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Geurts DEM, Huys QJM, den Ouden HEM, Cools R. Serotonin and aversive Pavlovian control of instrumental behavior in humans. J Neurosci 2013; 33:18932-9. [PMID: 24285898 PMCID: PMC6618702 DOI: 10.1523/jneurosci.2749-13.2013] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 10/17/2013] [Accepted: 10/17/2013] [Indexed: 11/21/2022] Open
Abstract
Adaptive decision-making involves interaction between systems regulating Pavlovian and instrumental control of behavior. Here we investigate in humans the role of serotonin in such Pavlovian-instrumental transfer in both the aversive and the appetitive domain using acute tryptophan depletion, known to lower central serotonin levels. Acute tryptophan depletion attenuated the inhibiting effect of aversive Pavlovian cues on instrumental behavior, while leaving unaltered the activating effect of appetitive Pavlovian cues. These data suggest that serotonin is selectively involved in Pavlovian inhibition due to aversive expectations and have implications for our understanding of the mechanisms underlying a range of affective, impulsive, and aggressive neuropsychiatric disorders.
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Affiliation(s)
- Dirk E M Geurts
- Radboud University Nijmegen Medical Centre, Donders Institute for Brain, Cognition and Behavior, Centre for Cognitive Neuroimaging and Department of Psychiatry, 6500 HB, Nijmegen, The Netherlands, Gatsby Computational Neuroscience Unit and Wellcome Trust Centre for Neuroimaging, UCL, WC1N 3AR, London, United Kingdom, Translational Neuromodeling Unit, ETH, University of Zurich, CH-8032 Zurich, Switzerland, and Psychiatry, Psychotherapy and Psychosomatics, University Hospital of Psychiatry Zurich, CH-8032 Zurich, Switzerland
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Acute tryptophan depletion increases translational indices of anxiety but not fear: serotonergic modulation of the bed nucleus of the stria terminalis? Neuropsychopharmacology 2012; 37:1963-71. [PMID: 22491355 PMCID: PMC3376328 DOI: 10.1038/npp.2012.43] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Serotonin is strongly implicated in the mammalian stress response, but surprisingly little is known about its mode of action. Recent data suggest that serotonin can inhibit aversive responding in humans, but this remains underspecified. In particular, data in rodents suggest that global serotonin depletion may specifically increase long-duration bed nucleus of the stria terminalis (BNST)-mediated aversive responses (ie, anxiety), but not short-duration BNST-independent responses (ie, fear). Here, we extend these findings to humans. In a balanced, placebo-controlled crossover design, healthy volunteers (n=20) received a controlled diet with and without the serotonin precursor tryptophan (acute tryptophan depletion; ATD). Aversive states were indexed by translational acoustic startle measures. Fear and anxiety were operationally defined as the increase in startle reactivity during short- and long-duration threat periods evoked by predictable shock (fear-potentiated startle) and by the context in which the shocks were administered (anxiety-potentiated startle), respectively. ATD significantly increased long-duration anxiety-potentiated startle but had no effect on short-duration fear-potentiated startle. These results suggest that serotonin depletion in humans selectively increases anxiety but not fear. Current translational frameworks support the proposition that ATD thus disinhibits dorsal raphé-originating serotonergic control of corticotropin-releasing hormone-mediated excitation of the BNST. This generates a candidate neuropharmacological mechanism by which depleted serotonin may increase response to sustained threats, alongside clear implications for our understanding of the manifestation and treatment of mood and anxiety disorders.
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Abstract
BACKGROUND Depression and anxiety disorders (ADs) are highly co-morbid, but the reason for this co-morbidity is unclear. One possibility is that they predispose one another. An informative way to examine interactions between disorders without the confounds present in patient populations is to manipulate the psychological processes thought to underlie the pathological states in healthy individuals. In this study we therefore asked whether a model of the sad mood in depression can enhance psychophysiological responses (startle) to a model of the anxiety in ADs. We predicted that sad mood would increase anxious anxiety-potentiated startle responses. METHOD In a between-subjects design, participants (n=36) completed either a sad mood induction procedure (MIP; n=18) or a neutral MIP (n=18). Startle responses were assessed during short-duration predictable electric shock conditions (fear-potentiated startle) or long-duration unpredictable threat of shock conditions (anxiety-potentiated startle). RESULTS Induced sadness enhanced anxiety- but not fear-potentiated startle. CONCLUSIONS This study provides support for the hypothesis that sadness can increase anxious responding measured by the affective startle response. This, taken together with prior evidence that ADs can contribute to depression, provides initial experimental support for the proposition that ADs and depression are frequently co-morbid because they may be mutually reinforcing.
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Affiliation(s)
- O J Robinson
- Section on Neurobiology of Fear and Anxiety, National Institute of Mental Health, NIH, Bethesda, MD, USA.
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Abstract
Pharmacological cognitive enhancers (PCEs) are used to improve cognitive functions, such as attention, learning, memory and planning in patients with impairments in cognition resulting from traumatic brain injury (TBI) or from neuropsychiatric disorders such as Alzheimer's disease (AD), mild cognitive impairment, schizophrenia, and attention deficit hyperactivity disorder (ADHD). Moreover, PCEs have been shown to improve cognition in healthy volunteers with no psychiatric disorders. This article describes the rationale behind the need for their use in neuropsychiatric patients and illustrates how PCEs can ameliorate cognitive impairments, improve quality of life and wellbeing, and therefore reduce the economic burden associated with these disorders. We also describe evidence that PCEs are being used as cognitive enhancers by healthy people. Crucially, as the lifestyle use of these drugs becomes very popular in the healthy population, a final aim is to present an overview of the current and future neuroethical considerations of enhancing the healthy brain. As information regarding their actual use, benefits and harms in various healthy populations is currently lacking, we propose research that aims to obtain relevant empirical data, monitor the short- and long-term effectiveness and side-effects, and initiate accurate surveys to determine current patterns and quantity of usage of PCE drugs by healthy people. Furthermore, in order to instigate a dialogue between neuroethics and neuropsychopharmacology, we urge scientists to explore and communicate the social and ethical implications of their research to the public. Finally, we discuss and highlight other means of enhancing cognition in both patients and healthy adults, including education and physical exercise.
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Robinson OJ, Cools R, Sahakian BJ. Tryptophan depletion disinhibits punishment but not reward prediction: implications for resilience. Psychopharmacology (Berl) 2012; 219:599-605. [PMID: 21769566 PMCID: PMC3249152 DOI: 10.1007/s00213-011-2410-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 06/17/2011] [Indexed: 11/30/2022]
Abstract
RATIONALE We have previously shown that tryptophan depletion enhances punishment but not reward prediction (Cools et al. in Neuropsychopharmacology 33:2291-2299, 2008b). This provided evidence for a valence-specific role of serotonin (which declines under depleted tryptophan) in aversive processing. Recent theoretical (Dayan and Huys in PLoS Comput Biol 4:e4, 2008) and experimental (Crockett et al. in J Neurosci 29:11993-11999, 2009) approaches have, however, further specified this role by showing that serotonin is critical for punishment-induced inhibition. OBJECTIVES We sought to examine the role of serotonin in punishment-induced inhibition. We also examined the impact of induced mood on this effect to assess whether effects of tryptophan depletion on affective inhibition are moderated by mood. METHODS Healthy females consumed a balanced amino acid mixture with (N = 20) or without (N = 21) the serotonin precursor tryptophan. Each subject completed either negative or neutral mood induction. All subjects completed the reward and punishment reversal learning task adopted in the previous study. RESULTS We demonstrate a punishment prediction impairment in individuals who consumed tryptophan which was absent in individuals who were depleted of tryptophan. This effect was impervious to mood state. CONCLUSIONS Our results suggest that serotonin promotes the inhibition of responses to punishing outcomes. This may lead to reduced punishment prediction accuracy in the presence of tryptophan and may contribute to resilience to affective disorders. Reduction of serotonin via tryptophan depletion then removes this inhibition. As such, we highlight a mechanism by which reduced serotonin can contribute to disorders of impulsivity and compulsivity as well as disorders of emotion.
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Affiliation(s)
- Oliver J. Robinson
- Department of Psychiatry and MRC/Wellcome Trust Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, Addenbrooke’s Hospital, P.O. Box 189, Level E4, Hills Road, Cambridge, CB2 2QQ UK ,National Institute of Mental Health, National Institutes of Health, Bethesda, MD USA
| | - Roshan Cools
- Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, Department of Psychiatry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Barbara J. Sahakian
- Department of Psychiatry and MRC/Wellcome Trust Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, Addenbrooke’s Hospital, P.O. Box 189, Level E4, Hills Road, Cambridge, CB2 2QQ UK
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Badawy AAB, Dougherty DM, Richard DM. Specificity of the acute tryptophan and tyrosine plus phenylalanine depletion and loading tests I. Review of biochemical aspects and poor specificity of current amino Acid formulations. Int J Tryptophan Res 2011; 2010:23-34. [PMID: 20676231 PMCID: PMC2911801 DOI: 10.4137/ijtr.s5134] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The acute tryptophan or tyrosine plus phenylalanine depletion and loading tests are powerful tools for studying the roles of serotonin, dopamine and noradrenaline in normal subjects and those with behavioural disorders. The current amino acid formulations for these tests, however, are associated with undesirable decreases in ratios of tryptophan or tyrosine plus phenylalanine to competing amino acids resulting in loss of specificity. This could confound biochemical and behavioural findings. Compositions of current formulations are reviewed, the biochemical principles underpinning the tests are revisited and examples of unintended changes in the above ratios and their impact on monoamine function and behaviour will be demonstrated from data in the literature. The presence of excessive amounts of the 3 branched-chain amino acids Leu, Ile and Val is responsible for these unintended decreases and the consequent loss of specificity. Strategies for enhancing the specificity of the different formulations are proposed.
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Badawy AAB, Dougherty DM, Richard DM. Specificity of the Acute Tryptophan and Tyrosine Plus Phenylalanine Depletion and Loading Tests Part II: Normalisation of the Tryptophan and the Tyrosine Plus Phenylalanine to Competing Amino Acid Ratios in a New Control Formulation. Int J Tryptophan Res 2011; 3:35-47. [PMID: 20725610 PMCID: PMC2923411 DOI: 10.4137/ijtr.s5169] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Current formulations for acute tryptophan (Trp) or tyrosine (Tyr) plus phenylalanine (Phe) depletion and loading cause undesirable decreases in ratios of Trp or Tyr + Phe to competing amino acids (CAA), thus undermining the specificities of these tests. Branched-chain amino acids (BCAA) cause these unintended decreases, and lowering their content in a new balanced control formulation in the present study led to normalization of all ratios. Four groups (n = 12 each) of adults each received one of four 50 g control formulations, with 0% (traditional), 20%, 30%, or 40% less of the BCAA. The free and total [Trp]/[CAA] and [Phe + Tyr]/[BCAA + Trp] ratios all decreased significantly during the first 5 h following the traditional formulation, but were fully normalized by the formulation containing 40% less of the BCAA. We recommend the latter as a balanced control formulation and propose adjustments in the depletion and loading formulations to enhance their specificities for 5-HT and the catecholamines.
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Robinson OJ, Letkiewicz AM, Overstreet C, Ernst M, Grillon C. The effect of induced anxiety on cognition: threat of shock enhances aversive processing in healthy individuals. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2011; 11:217-27. [PMID: 21484411 PMCID: PMC3169349 DOI: 10.3758/s13415-011-0030-5] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Individuals with anxiety disorders demonstrate altered cognitive performance including (1) cognitive biases towards negative stimuli (affective biases) and (2) increased cognitive rigidity (e.g., impaired conflict adaptation) on affective Stroop tasks. Threat of electric shock is frequently used to induce anxiety in healthy individuals, but the extent to which this manipulation mimics the cognitive impairment seen in anxiety disorders is unclear. In this study, 31 healthy individuals completed an affective Stroop task under safe and threat-of-shock conditions. We showed that threat (1) enhanced aversive processing and abolished a positive affective bias but (2) had no effect on conflict adaptation. Threat of shock thus partially models the effects of anxiety disorders on affective Stroop tasks. We suggest that the affective state of anxiety-which is common to both threat and anxiety disorders-modulates the neural inhibition of subcortical aversive processing, whilst pathologies unique to anxiety disorders modulate conflict adaptation.
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Affiliation(s)
- Oliver J Robinson
- Mood and Anxiety Disorders Program, NIMH, 15K North Drive, MSC 2670, Bethesda, MD 20892, USA.
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van der Plasse G, Feenstra MGP. WITHDRAWN: Is acute tryptophan depletion a valid method to assess central serotonergic function? Neurosci Biobehav Rev 2011:S0149-7634(11)00053-4. [PMID: 21435352 DOI: 10.1016/j.neubiorev.2011.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/16/2011] [Accepted: 03/15/2011] [Indexed: 10/18/2022]
Abstract
This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Geoffrey van der Plasse
- Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Department of Psychiatry, PO Box 85500, 3508 GAUtrecht,The Netherlands
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Psychological stress-induced, IDO1-dependent tryptophan catabolism: implications on immunosuppression in mice and humans. PLoS One 2010; 5:e11825. [PMID: 20689575 PMCID: PMC2911374 DOI: 10.1371/journal.pone.0011825] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 07/01/2010] [Indexed: 12/17/2022] Open
Abstract
It is increasingly recognized that psychological stress influences inflammatory responses and mood. Here, we investigated whether psychological stress (combined acoustic and restraint stress) activates the tryptophan (Trp) catabolizing enzyme indoleamine 2,3-dioxygenase 1(IDO1) and thereby alters the immune homeostasis and behavior in mice. We measured IDO1 mRNA expression and plasma levels of Trp catabolites after a single 2-h stress session and in repeatedly stressed (4.5-days stress, 2-h twice a day) naïve BALB/c mice. A role of cytokines in acute stress-induced IDO1 activation was studied after IFNγ and TNFα blockade and in IDO1−/− mice. RU486 and 1-Methyl-L-tryptophan (1-MT) were used to study role of glucocorticoids and IDO1 on Trp depletion in altering the immune and behavioral response in repeatedly stressed animals. Clinical relevance was addressed by analyzing IDO1 activity in patients expecting abdominal surgery. Acute stress increased the IDO1 mRNA expression in brain, lung, spleen and Peyer's patches (max. 14.1±4.9-fold in brain 6-h after stress) and resulted in a transient depletion of Trp (−25.2±6.6%) and serotonin (−27.3±4.6%) from the plasma measured 6-h after stress while kynurenine levels increased 6-h later (11.2±9.3%). IDO1 mRNA up-regulation was blocked by anti-TNFα and anti-IFNγ treatment. Continuous IDO1 blockade by 1-MT but not RU486 treatment normalized the anti-bacterial defense and attenuated increased IL-10 inducibility in splenocytes after repeated stress as it reduced the loss of body weight and behavioral alterations. Moreover, kynurenic acid which remained increased in 1-MT treated repeatedly stressed mice was identified to reduce the TNFα inducibility of splenocytes in vitro and in vivo. Thus, psychological stress stimulates cytokine-driven IDO1 activation and Trp depletion which seems to have a central role for developing stress-induced immunosuppression and behavioral alteration. Since patients showed Trp catabolism already prior to surgery, IDO is also a possible target enzyme for humans modulating immune homeostasis and mood.
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