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d'Angelo LSC, Savulich G, Sahakian BJ. Lifestyle use of drugs by healthy people for enhancing cognition, creativity, motivation and pleasure. Br J Pharmacol 2017; 174:3257-3267. [PMID: 28427114 DOI: 10.1111/bph.13813] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 03/22/2017] [Accepted: 03/29/2017] [Indexed: 12/24/2022] Open
Abstract
Today, there is continued, and in some cases growing, availability of not only psychoactive substances, including treatments for mental health disorders such as cognitive enhancers, which can enhance or restore brain function, but also 'recreational' drugs such as novel psychoactive substances (NPS). The use of psychoactive drugs has both benefits and risks: whilst new drugs to treat cognitive symptoms in neuropsychiatric or neurodegenerative disorders could have great benefits for many patient groups, the increasing ease of accessibility to recreational NPS and the increasing lifestyle use of cognitive enhancers by healthy people means that the effective management of psychoactive substances will be an issue of increasing importance. Clearly, the potential benefits of cognitive enhancers are large and increasingly relevant, particularly as the population ages, and for this reason, we should continue to devote resources to the development of cognitive enhancers as treatments for neurodegenerative diseases and psychiatric disorders, including Alzheimer's disease, attention deficit hyperactivity disorder and schizophrenia. However, the increasing use of cognitive enhancers by healthy individuals raises safety, ethical and regulatory concerns, which should not be ignored. Similarly, understanding the short- and long-term consequences of the use of NPS, as well as better understanding the motivations and profiles of users could promote more effective prevention and harm reduction measures. Linked Articles This article is part of a themed section on Pharmacology of Cognition: a Panacea for Neuropsychiatric Disease? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.19/issuetoc.
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Affiliation(s)
- L-S Camilla d'Angelo
- Department of Psychiatry and Behavioural and Clinical Neuroscience Institute, University of Cambridge, UK
| | - George Savulich
- Department of Psychiatry and Behavioural and Clinical Neuroscience Institute, University of Cambridge, UK
| | - Barbara J Sahakian
- Department of Psychiatry and Behavioural and Clinical Neuroscience Institute, University of Cambridge, UK
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Dissociable rate-dependent effects of oral methylphenidate on impulsivity and D2/3 receptor availability in the striatum. J Neurosci 2015; 35:3747-55. [PMID: 25740505 DOI: 10.1523/jneurosci.3890-14.2015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We have previously shown that impulsivity in rats is linked to decreased dopamine D2/3 receptor availability in the ventral striatum. In the present study, we investigated, using longitudinal positron emission tomography (PET), the effects of orally administered methylphenidate (MPH), a first-line treatment for attention deficit hyperactivity disorder, on D2/3 receptor availability in the dorsal and ventral striatum and related these changes to impulsivity. Rats were screened for impulsive behavior on a five-choice serial reaction time task. After a baseline PET scan with the D2/3 ligand [(18)F]fallypride, rats received 6 mg/kg MPH, orally, twice each day for 28 d. Rats were then reassessed for impulsivity and underwent a second [(18)F]fallypride PET scan. Before MPH treatment, we found that D2/3 receptor availability was significantly decreased in the left but not the right ventral striatum of high-impulse (HI) rats compared with low-impulse (LI) rats. MPH treatment increased impulsivity in LI rats, and modulated impulsivity and D2/3 receptor availability in the dorsal and ventral striatum of HI rats through inverse relationships with baseline levels of impulsivity and D2/3 receptor availability, respectively. However, we found no relationship between the effects of MPH on impulsivity and D2/3 receptor availability in any of the striatal subregions investigated. These findings indicate that trait-like impulsivity is associated with decreased D2/3 receptor availability in the left ventral striatum, and that stimulant drugs modulate impulsivity and striatal D2/3 receptor availability through independent mechanisms.
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Arnold LE, Gadow KD, Farmer CA, Findling RL, Bukstein O, Molina BS, Brown NV, Li X, Rundberg-Rivera EV, Bangalore S, Buchan-Page K, Hurt EA, Rice R, McNamara NK, Aman MG. Comorbid anxiety and social avoidance in treatment of severe childhood aggression: response to adding risperidone to stimulant and parent training; mediation of disruptive symptom response. J Child Adolesc Psychopharmacol 2015; 25:203-12. [PMID: 25885010 PMCID: PMC4403224 DOI: 10.1089/cap.2014.0104] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE In the four-site Treatment of Severe Childhood Aggression (TOSCA) study, addition of risperidone to stimulant and parent training moderately improved parent-rated disruptive behavior disorder (DBD) symptoms. This secondary study explores outcomes other than DBD and attention-deficit/hyperactivity disorder (ADHD) as measured by the Child and Adolescent Symptom Inventory-4R (CASI-4R). METHODS A total of 168 children ages 6-12 with severe aggression (physical harm), DBD, and ADHD were randomized to parent training plus stimulant plus placebo (basic treatment) or parent training plus stimulant plus risperidone (augmented treatment) for 9 weeks. All received only parent training plus stimulant for the first 3 weeks, then those with room for improvement received a second drug (placebo or risperidone) for 6 weeks. CASI-4R category item means at baseline and week 9 were entered into linear mixed-effects models for repeated measures to evaluate group differences in changes. Mediation of the primary DBD outcome was explored. RESULTS Parent ratings were nonsignificant with small/negligible effects, but teacher ratings (n=46 with complete data) showed significant augmented treatment advantage for symptoms of anxiety (p=0.013, d=0.71), schizophrenia spectrum (p=0.017, d=0.45), and impairment in these domains (p=0.02, d=0.26), all remaining significant after false discovery rate correction for multiple tests. Improvement in teacher-rated anxiety significantly (p=0.001) mediated the effect of risperidone augmentation on the primary outcome, the Disruptive-total of the parent-rated Nisonger Child Behavior Rating Form. CONCLUSIONS Addition of risperidone to parent training plus stimulant improves not only parent-rated DBD as previously reported, but also teacher-rated anxiety-social avoidance. Improvement in anxiety mediates improvement in DBD, suggesting anxiety-driven fight-or-flight disruptive behavior with aggression, with implications for potential treatment strategies. Clinicians should attend to possible anxiety in children presenting with aggression and DBD. CLINICAL TRIAL REGISTRY Treatment of Severe Childhood Aggression (The TOSCA Study). NCT00796302. clinicaltrials.gov.
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Affiliation(s)
| | | | | | - Robert L. Findling
- Division of Child and Adolescent Psychiatry, Johns Hopkins University, Baltimore, Maryland.,Department of Psychiatry, Kennedy Krieger Institute, Baltimore, Maryland
| | - Oscar Bukstein
- University of Texas-Houston Medical School, Houston, Texas
| | - Brooke S.G. Molina
- Department of Psychiatry and Psychology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Nicole V. Brown
- Biostastics Center, Ohio State University Medical Center, Columbus, Ohio
| | - Xiaobai Li
- Department of Psychiatry, Ohio State University, Columbus, Ohio
| | | | - Srihari Bangalore
- Department of Psychiatry and Psychology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | | | | | - Robert Rice
- Department of Psychiatry, Ohio State University, Columbus, Ohio
| | - Nora K. McNamara
- Case Western Reserve University, Department of Psychiatry, Cleveland, Ohio
| | - Michael G. Aman
- The Nisonger Center (OCEDD), Ohio State University, Columbus, Ohio
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del Campo N, Fryer TD, Hong YT, Smith R, Brichard L, Acosta-Cabronero J, Chamberlain SR, Tait R, Izquierdo D, Regenthal R, Dowson J, Suckling J, Baron JC, Aigbirhio FI, Robbins TW, Sahakian BJ, Müller U. A positron emission tomography study of nigro-striatal dopaminergic mechanisms underlying attention: implications for ADHD and its treatment. ACTA ACUST UNITED AC 2013; 136:3252-70. [PMID: 24163364 PMCID: PMC4125626 DOI: 10.1093/brain/awt263] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Through the combined use of 18F-fallypride positron emission tomography and magnetic resonance imaging this study examined the neural mechanisms underlying the attentional deficits associated with attention deficit/hyperactivity disorder and their potential reversal with a single therapeutic dose of methylphenidate. Sixteen adult patients with attention deficit/hyperactivity disorder and 16 matched healthy control subjects were positron emission tomography and magnetic resonance imaging scanned and tested on a computerized sustained attention task after oral methylphenidate (0.5 mg/kg) and placebo administration in a within-subject, double-blind, cross-over design. Although patients with attention deficit/hyperactivity disorder as a group showed significant attentional deficits and reduced grey matter volume in fronto-striato-cerebellar and limbic networks, they had equivalent D2/D3 receptor availability and equivalent increases in endogenous dopamine after methylphenidate treatment to that observed in healthy control subjects. However, poor attentional performers drawn from both the attention deficit/hyperactivity disorder and the control groups had significantly reduced left caudate dopamine activity. Methylphenidate significantly increased dopamine levels in all nigro-striatal regions, thereby normalizing dopamine levels in the left caudate in low performers. Behaviourally, methylphenidate improved sustained attention in a baseline performance-dependent manner, irrespective of diagnosis. This finding was accompanied by an equally performance-dependent effect of the drug on dopamine release in the midbrain, whereby low performers showed reduced dopamine release in this region. Collectively, these findings support a dimensional model of attentional deficits and underlying nigro-striatal dopaminergic mechanisms of attention deficit/hyperactivity disorder that extends into the healthy population. Moreover, they confer midbrain dopamine autoreceptors a hitherto neglected role in the therapeutic effects of oral methylphenidate in attention deficit/hyperactivity disorder. The absence of significant case–control differences in D2/D3 receptor availability (despite the observed relationships between dopamine activity and attention) suggests that dopamine dysregulation per se is unlikely to be the primary cause underlying attention deficit/hyperactivity disorder pathology in adults. This conclusion is reinforced by evidence of neuroanatomical changes in the same set of patients with attention deficit/hyperactivity disorder.
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Affiliation(s)
- Natalia del Campo
- 1 Department of Psychiatry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
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Wickens JR, Hyland BI, Tripp G. Animal models to guide clinical drug development in ADHD: lost in translation? Br J Pharmacol 2012; 164:1107-28. [PMID: 21480864 DOI: 10.1111/j.1476-5381.2011.01412.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We review strategies for developing animal models for examining and selecting compounds with potential therapeutic benefit in attention-deficit hyperactivity disorder (ADHD). ADHD is a behavioural disorder of unknown aetiology and pathophysiology. Current understanding suggests that genetic factors play an important role in the aetiology of ADHD. The involvement of dopaminergic and noradrenergic systems in the pathophysiology of ADHD is probable. We review the clinical features of ADHD including inattention, hyperactivity and impulsivity and how these are operationalized for laboratory study. Measures of temporal discounting (but not premature responding) appear to predict known drug effects well (treatment validity). Open-field measures of overactivity commonly used do not have treatment validity in human populations. A number of animal models have been proposed that simulate the symptoms of ADHD. The most commonly used are the spontaneously hypertensive rat (SHR) and the 6-hydroxydopamine-lesioned (6-OHDA) animals. To date, however, the SHR lacks treatment validity, and the effects of drugs on symptoms of impulsivity and inattention have not been studied extensively in 6-OHDA-lesioned animals. At the present stage of development, there are no in vivo models of proven effectiveness for examining and selecting compounds with potential therapeutic benefit in ADHD. However, temporal discounting is an emerging theme in theories of ADHD, and there is good evidence of increased value of delayed reward following treatment with stimulant drugs. Therefore, operant behaviour paradigms that measure the effects of drugs in situations of delayed reinforcement, whether in normal rats or selected models, show promise for the future.
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Abstract
In recent years, descriptive symptom-based approaches of attention deficit hyperactivity disorder (ADHD) have been increasingly replaced by more sophisticated endophenotype-based strategies, better suited to investigate its pathophysiological basis, which is inherently heterogeneous. Measurements derived from neuroimaging techniques such as positron emission tomography (PET) and magnetic resonance imaging (MRI) constitute endophenotypes of growing interest, capable of providing unprecedented windows on neurochemical and neuroanatomical components of psychiatric conditions. This chapter reviews the current state of knowledge regarding putative neural and behavioral endophenotypes of ADHD, across the lifespan. To this end, recent evidence drawn from molecular and structural neuroimaging studies are discussed in the light of widely accepted neuropsychological and pharmacological models of ADHD.
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Affiliation(s)
- Natalia del Campo
- Department of Psychiatry, and Behavioral and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK,
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Swanson J, Baler RD, Volkow ND. Understanding the effects of stimulant medications on cognition in individuals with attention-deficit hyperactivity disorder: a decade of progress. Neuropsychopharmacology 2011; 36:207-26. [PMID: 20881946 PMCID: PMC3055506 DOI: 10.1038/npp.2010.160] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 08/08/2010] [Accepted: 08/09/2010] [Indexed: 11/09/2022]
Abstract
The use of stimulant drugs for the treatment of children with attention-deficit hyperactivity disorder (ADHD) is one of the most widespread pharmacological interventions in child psychiatry and behavioral pediatrics. This treatment is well grounded on controlled studies showing efficacy of low oral doses of methylphenidate and amphetamine in reducing the behavioral symptoms of the disorder as reported by parents and teachers, both for the cognitive (inattention and impulsivity) and non-cognitive (hyperactivity) domains. Our main aim is to review the objectively measured cognitive effects that accompany the subjectively assessed clinical responses to stimulant medications. Recently, methods from the cognitive neurosciences have been used to provide information about brain processes that underlie the cognitive deficits of ADHD and the cognitive effects of stimulant medications. We will review some key findings from the recent literature, and then offer interpretations of the progress that has been made over the past decade in understanding the cognitive effects of stimulant medication on individuals with ADHD.
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Affiliation(s)
- James Swanson
- Department of Pediatrics, University of California, Irvine, CA, USA
| | - Ruben D Baler
- National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD, USA
| | - Nora D Volkow
- National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD, USA
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Arnold LE, Farmer C, Kraemer HC, Davies M, Witwer A, Chuang S, DiSilvestro R, McDougle CJ, McCracken J, Vitiello B, Aman MG, Scahill L, Posey DJ, Swiezy NB. Moderators, mediators, and other predictors of risperidone response in children with autistic disorder and irritability. J Child Adolesc Psychopharmacol 2010; 20:83-93. [PMID: 20415603 PMCID: PMC2865212 DOI: 10.1089/cap.2009.0022] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE/BACKGROUND The National Institute of Mental Health (NIMH) Research Units on Pediatric Psychopharmacology (RUPP) Autism Network found an effect size of d = 1.2 in favor of risperidone on the main outcome measure in an 8-week double-blind, placebo-controlled trial for irritability in autistic disorder. This paper explores moderators and mediators of this effect. METHOD Intention-to-treat (ITT) analyses were conducted with suspected moderators and mediators entered into the regression equations. MacArthur Foundation Network subgroup guidelines were followed in the evaluation of the results. RESULTS Only baseline severity moderated treatment response: Higher severity showed greater improvement for risperidone but not for placebo. Weight gain mediated treatment response negatively: those who gained more weight improved less with risperidone and more with placebo. Compliance correlated with outcome for risperidone but not placebo. Higher dose correlated with worse outcome for placebo, but not risperidone. Of nonspecific predictors, parent education, family income, and low baseline prolactin positively predicted outcome; anxiety, bipolar symptoms, oppositional-defiant symptoms, stereotypy, and hyperactivity negatively predicted outcome. Risperidone moderated the effect of change in 5'-nucleotidase, a marker of zinc status, for which decrease was associated with improvement only with risperidone, not with placebo. CONCLUSION The benefit-risk ratio of risperidone is better with greater symptom severity. Risperidone can be individually titrated to optimal dosage for excellent response in the majority of children. Weight gain is not necessary for risperidone benefit and may even detract from it. Socioeconomic advantage, low prolactin, and absence of co-morbid problems nonspecifically predict better outcome. Mineral interactions with risperidone deserve further study.
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Affiliation(s)
- L. Eugene Arnold
- Department of Psychiatry, Ohio State University, Columbus, Ohio.,The Nisonger Center, Ohio State University, Columbus, Ohio
| | - Cristan Farmer
- The Nisonger Center, Ohio State University, Columbus, Ohio
| | - Helena Chmura Kraemer
- Department of Psychiatry and Behavioral Sciences (Emerita), Stanford University, Palo Alton, California; Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | - Andrea Witwer
- The Nisonger Center, Ohio State University, Columbus, Ohio
| | | | | | | | - James McCracken
- Department of Psychiatry and Behavioral Sciences, University of California Semel Institute, Los Angeles, California
| | - Benedetto Vitiello
- Child and Adolescent Treatment and Preventive Intervention Research Branch, National Institute of Mental Health, Rockville, Maryland
| | | | - Lawrence Scahill
- Yale Child Study Center, Yale University, New Haven, Connecticut
| | - David J. Posey
- Department of Psychiatry, Indiana University, Indianapolis, Indiana
| | - Naomi B. Swiezy
- Department of Psychiatry, Indiana University, Indianapolis, Indiana
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Fan X, Hess EJ. D2-like dopamine receptors mediate the response to amphetamine in a mouse model of ADHD. Neurobiol Dis 2006; 26:201-11. [PMID: 17291774 PMCID: PMC1876677 DOI: 10.1016/j.nbd.2006.12.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 12/05/2006] [Accepted: 12/20/2006] [Indexed: 11/16/2022] Open
Abstract
The mechanisms underlying the effects of psychostimulants in attention deficit hyperactivity disorder (ADHD) are not well understood, but indirect evidence implicates D2 dopamine receptors. Here we dissect the components of dopaminergic neurotransmission in the hyperactive mouse mutant coloboma to identify pre- and postsynaptic elements essential for the effects of amphetamine in these mice. Amphetamine treatment reduced locomotor activity in coloboma mice, but induced a robust increase in dopamine overflow suggesting that abnormal regulation of dopamine efflux does not account for the behavioral effect. However, the D2-like dopamine receptor antagonists haloperidol and raclopride, but not the D1-like dopamine receptor antagonist SCH23390, blocked the amphetamine-induced reduction in locomotor activity in coloboma mice, providing direct evidence that D2-like dopamine receptors mediate the effect of amphetamine in these mice. With the precedent established that it is possible to directly antagonize this response, this strategy should prove useful for identifying novel therapeutics in ADHD.
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Affiliation(s)
- Xueliang Fan
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Ellen J. Hess
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21287
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Winstanley CA, Dalley JW, Theobald DEH, Robbins TW. Global 5-HT depletion attenuates the ability of amphetamine to decrease impulsive choice on a delay-discounting task in rats. Psychopharmacology (Berl) 2003; 170:320-331. [PMID: 12955303 DOI: 10.1007/s00213-003-1546-3] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2003] [Accepted: 05/20/2003] [Indexed: 11/28/2022]
Abstract
RATIONALE Psychomotor stimulant drugs such as methylphenidate and amphetamine decrease impulsive behaviour in attention deficit hyperactivity disorder patients by unknown mechanisms. Although most behavioural effects of amphetamine are attributed to the dopaminergic system, some recent evidence suggests a role for serotonin in this paradoxical "calming" effect. OBJECTIVES To investigate whether forebrain serotonin depletion affects the action of amphetamine in the rat on a delayed reward task where impulsive choice is measured as the selection of a smaller immediate over a larger delayed reward. METHODS . Following behavioural training, rats received i.c.v. infusions of either vehicle (n=10) or the serotonergic neurotoxin 5,7-DHT (n=10). Post-operatively, animals received i.p. d-amphetamine (0.3,1.0,1.5, and 2.3 mg/kg/ml), and d-amphetamine co-administered with the dopamine antagonist cis-z-flupenthixol. RESULTS 5,7-DHT (i.c.v.) itself did not affect choice behaviour, despite depleting forebrain serotonin levels by over 85%. Amphetamine increased choice for the large reward, i.e. decreased impulsivity. This effect was attenuated by 5-HT depletion, particularly in animals showing a high level of impulsive choice. Co-administration of cis-z-flupenthixol (0.125 mg/kg) with d-amphetamine abolished the effect of amphetamine in the lesioned group, whereas this was only partially attenuated in the vehicle control group. CONCLUSIONS These data suggest that the ability of amphetamine to decrease impulsivity is not solely due to its effects on dopaminergic systems, but may also depend on serotonergic neurotransmission.
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Affiliation(s)
- Catharine A Winstanley
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK
| | - Jeffrey W Dalley
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK
| | - David E H Theobald
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK
| | - Trevor W Robbins
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK
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Wigal T, Swanson JM, Regino R, Lerner MA, Soliman I, Steinhoff K, Gurbani S, Wigal SB. Stimulant medications for the treatment of ADHD: Efficacy and limitations. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1098-2779(1999)5:3<215::aid-mrdd8>3.0.co;2-k] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abstract
Although hyperkinesis is expressed in several neurological disorders, the biological basis of this phenotype is unknown. The mouse mutant coloboma (Cml+) exhibits profound spontaneous locomotor hyperactivity resulting from a deletion mutation. This deletion encompasses several genes including Snap, which encodes SNAP-25, a nerve terminal protein involved in neurotransmitter release. Administration of amphetamine, a drug that acts presynaptically, markedly reduced the locomotor activity in coloboma mice but increased the activity of control mice implicating presynaptic function in the behavioral abnormality. In contrast, the psychostimulant methylphenidate increased locomotor activity in both coloboma and control mice. When a transgene encoding SNAP-25 was bred into the coloboma strain to complement the Snap deletion, the hyperactivity expressed by these mice was rescued, returning these corrected mice to normal levels of locomotor activity. These results demonstrate that the hyperactivity exhibited by these mice is the result of abnormalities in presynaptic function specifically attributable to deficits in SNAP-25 expression.
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Abstract
Clinical, animal and neuroanatomical studies of differential isomer and dosage effects of CNS stimulant medications on behaviour are reviewed. Wender's hypothesis that an underlying biochemical abnormality and a disorder of reinforcement was the primary deficit in "MBD" children is restated in terms of a disorder of polysynaptic dopaminergic circuits, between prefrontal and striate centres. Wender's notion of a disorder of reinforcement is broadened to include a disorder of planning and correction of behaviour, including capacity for cortical control of automatic instinctual motor programmes. The dopamine hypothesis of Attention Deficit Hyperactivity Disorder (ADHD) is examined from the point of view of differential dose effects of CNS stimulant medications, and theories of neural control. Clinical, animal and neuropharmacological studies are reviewed. Implications of the findings for understanding clinical and side effects in ADHD children of stimulants are discussed.
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Affiliation(s)
- F Levy
- Department of Child and Adolescent Psychiatry, University of New South Wales, Randwick
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Douglas VI, Barr RG, O'Neill ME, Britton BG. Short term effects of methylphenidate on the cognitive, learning and academic performance of children with attention deficit disorder in the laboratory and the classroom. J Child Psychol Psychiatry 1986; 27:191-211. [PMID: 3514644 DOI: 10.1111/j.1469-7610.1986.tb02330.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Sixteen children meeting diagnostic criteria for Attention Deficit Disorder with Hyperactivity (ADD-H) were tested on methylphenidate (0.3 mg/kg) and placebo on cognitive, learning, academic and behavioral measures in a double-blind study. Assessments were carried out in the laboratory and in the children's regular classrooms. Results indicate methylphenidate-induced improvements on a majority of the measures. Drug-induced changes reflected increased output, accuracy and efficiency and improved learning acquisition. There was also evidence of increased effort and self-correcting behaviours. It is argued that reviewers have underestimated the potential of stimulants to improve the performance of ADD-H children on academic, learning and cognitive tasks.
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Raskin LA. The influence of environmental variables on amphetamine-induced activity in the preweanling rat. Pharmacol Biochem Behav 1983; 19:187-91. [PMID: 6634870 DOI: 10.1016/0091-3057(83)90037-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The present experiments investigated how environmental stimuli influence a behavioral response to amphetamine treatment in preweanling rats. In the first experiment, 15-day-old rats received either 1 mg/kg d-amphetamine or saline and were observed in the presence of their home shavings or in a novel cage. Results showed that although familiar cues from the home bedding decreased activity of the saline treated pups, these cues did not influence the activity-enhancing effect of amphetamine. In Experiment 2, 15-day-old pups were placed in a cage with an anesthetized adult conspecific and non-directed activity, around the cage, as well as directed activity on top of the adult were recorded. Following amphetamine treatment, animals tested with a conspecific showed no increase in non-directed activity, a finding which replicates previous observations. In the present experiment, however, a significant increase was seen in the activity directed towards or on top of the anesthetized adult. These experiments reveal that familiar cues per se are not sufficient to influence amphetamine-induced activity in young rats. Activity is influenced, specifically if familiar cues are associated with a discrete object. In the presence of a familiar stimulus, non-directed activity is decreased and directed activity is enhanced. These data are discussed in terms of clinical findings which show that amphetamine acts to focus, or direct activity of the hyperactive child, and further underlines the importance of environmental variables in influencing the amphetamine response.
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Abstract
Stereotyped movements are described in monkeys and humans and are classified as arising from constraint, sensory deprivation in infancy, amphetamine treatment or psychotic states. It is argued that, with the exception of cage stereotypies, stereotyped behaviour is evidence of abnormality in the nervous system consequent upon distorted maturational processes, organic defect or biochemical disturbance. Stereotypy is associated with a state of cognitive inflexibility and social and sensory isolation in humans and monkeys. It is suggested that, while no simple biochemical disturbance in the brain can describe these various occurrences of stereotypy, the cross-species occurrence of a syndrome of isolation, cognitive inflexibility and stereotypy implies a related mechanism mediating these divergent effects. If stereotypy is regarded as a consequence of failure to use sensory input to direct behaviour, therapeutic regimes designed to stimulate responsive behaviours and social interactions are more likely to be effective in the long run than direct attempts to suppress stereotypy.
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Dyme IZ, Sahakian BJ, Golinko BE, Rabe EF. Perseveration induced by methylphenidate in children: preliminary findings. Prog Neuropsychopharmacol Biol Psychiatry 1982; 6:269-73. [PMID: 6890702 DOI: 10.1016/s0278-5846(82)80177-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Robbins TW, Sahakian BJ. "Paradoxical" effects of psychomotor stimulant drugs in hyperactive children from the standpoint of behavioural pharmacology. Neuropharmacology 1979; 18:931-50. [PMID: 43484 DOI: 10.1016/0028-3908(79)90157-6] [Citation(s) in RCA: 130] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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