Memantine in the Treatment of Executive Function Deficits in Adults With ADHD

Current nonstimulant medications for adults with attention-deficit/hyperactivity disorder

INTRODUCTION

Stimulants, including methylphenidate and amphetamines, are the first-line pharmacological treatment of ADHD in adults. However, in patients who do not respond or poorly tolerate stimulants, non-stimulant medications are usually recommended.

AREAS COVERED

The authors provide a narrative review of the literature on non-stimulant treatments for adult ADHD, including controlled and observational clinical studies conducted on adult samples. Atomoxetine has been extensively studied and showed significant efficacy in treating adult ADHD. Issues related to dosing, treatment duration, safety, and use in the case of psychiatric comorbidity are summarized. Among other compounds indicated for ADHD in adults, antidepressants sharing at least a noradrenergic or dopaminergic component, including tricyclic compounds, bupropion, and viloxazine, have shown demonstratable efficacy. Evidence is also available for antihypertensives, particularly guanfacine, as well as memantine, metadoxine, and mood stabilizers, while negative findings have emerged for galantamine, antipsychotics, and cannabinoids.

EXPERT OPINION

While according to clinical guidelines, atomoxetine may serve as the only second-line option in adults with ADHD, several other nonstimulant compounds may be effectively used in order to personalize treatment based on comorbid conditions and ADHD features. Nevertheless, further research is needed to identify and test more personalized treatment strategies for adults with ADHD.

In Memoriam: Professor Joseph Biederman's Contributions to Child and Adolescent Psychiatry

OBJECTIVE

To provide an overview of Joe Biederman's contributions to child and adolescent psychiatry.

METHOD

Nine colleagues described his contributions to: psychopharmacology, comorbidity and genetics, pediatric bipolar disorder, autism spectrum disorders, Tourette's and tic disorders, clinical and neuro biomarkers for pediatric mood disorders, executive functioning, and adult ADHD.

RESULTS

Joe Biederman left us with many concrete indicators of his contributions to child and adolescent psychiatry. He set up the world's first pediatric psychopharmacology clinic and clinical research program in child adolescent psychiatry. As a young faculty member he began a research program that led to many awards and eventual promotion to full professor at Harvard Medical School. He was for many years the most highly cited researcher in ADHD. He achieved this while maintaining a full clinical load and was widely respected for his clinical acumen.

CONCLUSION

The world is a better place because Joe Biederman was here.

Molecular Mechanisms Underlying NMDARs Dysfunction and Their Role in ADHD Pathogenesis

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, although the aetiology of ADHD is not yet understood. One proposed theory for developing ADHD is N-methyl-D-aspartate receptors (NMDARs) dysfunction. NMDARs are involved in regulating synaptic plasticity and memory function in the brain. Abnormal expression or polymorphism of some genes associated with ADHD results in NMDAR dysfunction. Correspondingly, NMDAR malfunction in animal models results in ADHD-like symptoms, such as impulsivity and hyperactivity. Currently, there are no drugs for ADHD that specifically target NMDARs. However, NMDAR-stabilizing drugs have shown promise in improving ADHD symptoms with fewer side effects than the currently most widely used psychostimulant in ADHD treatment, methylphenidate. In this review, we outline the molecular and genetic basis of NMDAR malfunction and how it affects the course of ADHD. We also present new therapeutic options related to treating ADHD by targeting NMDAR.

Exploring the Relationship between Cardiorespiratory Fitness and Executive Functioning in Adults with ADHD

OBJECTIVE

Associations between measures of executive functioning (EF) and cardiorespiratory fitness (CRF) were examined for adults with and without ADHD.

METHOD

Measures of executive functioning including the Stroop task, Wisconsin Card Sorting task, and Operation Span Task were completed virtually (n = 36 ADHD; n = 36 Control). Participants completed the Six-Minute Walk Test to estimate CRF.

RESULTS

Mean performance measures of executive function did not differ by group. However, higher estimated CRF was associated with better Stroop task performance, and the association was strongest for individuals with ADHD.

CONCLUSION

In adults with ADHD, higher estimated CRF was associated with better inhibitory control, but not with other measures of executive functioning.

Do ADHD Treatments Improve Executive Behavior Beyond Core ADHD Symptoms in Adults? Evidence From Systematic Analysis of Clinical Trials

We sought to understand the effect of current treatments for attention deficit hyperactivity disorder (ADHD) on executive functioning deficits, which are often comorbid with ADHD, via a systematic analysis of adult ADHD treatment studies evaluating change in behavioral measures beyond the core symptoms of Diagnostic and Statistical Manual of Mental Disorders ADHD. The standardized mean difference for behavioral measures of executive functioning was determined from controlled trials of adults with ADHD and compared with effects on core ADHD symptoms. Several studies of atomoxetine revealed small to large standardized mean differences. Nonreplicated studies revealed small to medium effects for triple-bead mixed amphetamine salts, lisdexamfetamine, and forms of cognitive behavioral therapy. Proportional effect versus core ADHD symptoms ranged from 0.78 to 1.16 for atomoxetine, and from 0.65 to 1.44 across all the studies. ADHD treatments have effects on executive functioning behavior beyond core ADHD symptoms in adults. Clinicians can measure and treat this morbidity using available clinical tools.

Effects of methylphenidate on mismatch negativity and P3a amplitude of initially psychostimulant-naïve, adult ADHD patients

BACKGROUND

Deficient information processing in ADHD theoretically results in sensory overload and may underlie the symptoms of the disorder. Mismatch negativity (MMN) and P3a amplitude reflect an individual's detection and subsequent change in attention to stimulus change in their environment. Our primary aim was to explore MMN and P3a amplitude in adult ADHD patients and to examine the effects of methylphenidate (MPH) on these measures.

METHODS

Forty initially psychostimulant-naïve, adult ADHD patients without comorbid ASD and 42 matched healthy controls (HC) were assessed with an MMN paradigm at baseline. Both groups were retested after 6 weeks, in which patients were treated with MPH.

RESULTS

Neither significant group differences in MMN nor P3a amplitude were found at baseline. Although 6-week MPH treatment significantly reduced symptomatology and improved daily functioning of the patients, it did not significantly affect MMN amplitude; however, it did significantly reduce P3a amplitude compared to the HC. Furthermore, more severe ADHD symptoms were significantly associated with larger MMN amplitudes in the patients, both at baseline and follow-up.

CONCLUSION

We found no evidence for early information processing deficits in patients with ADHD, as measured with MMN and P3a amplitude. Six-week treatment with MPH decreased P3a but not MMN amplitude, although more severe ADHD-symptoms were associated with larger MMN amplitudes in the patients. Given that P3a amplitude represents an important attentional process and that glutamate has been linked to both ADHD and MMN amplitude, future research should investigate augmenting MPH treatment of less responsive adults with ADHD with glutamatergic antagonists.

Memantine for autism spectrum disorder

BACKGROUND

Autism spectrum disorder (ASD; also known as autism) is a developmental disability that begins in childhood and is typically seen in around 1% to 2% of children. It is characterised by social communication difficulties and repetitive and restricted behaviours and routines that can have a negative impact on a child's quality of life, achievement at school, and social interactions with others. It has been hypothesised that memantine, which is traditionally used to treat dementia, may be effective in reducing the core symptoms of autism as well as some co-occurring symptoms such as hyperactivity and language difficulties. If memantine is being used to treat the core symptoms of autism, it is important to review the evidence of its effectiveness.

OBJECTIVES

To assess the effects of memantine on the core symptoms of autism, including, but not limited to, social communication and stereotypical behaviours.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, nine other databases and three trials registers up to February 2022. We also checked reference lists of key studies and checked with experts in the field for any additional papers. We searched for retractions of the included studies in MEDLINE, Embase, and the Retraction Watch Database. No retractions or corrections were found.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of any dose of memantine compared with placebo in autistic people. We also included RCTs in which only one group received memantine, but both groups received the same additional therapy (e.g. a behaviour intervention).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were core autism symptoms and adverse effects. Secondary outcomes were language, intelligence, memory, adaptive behaviour, hyperactivity, and irritability. We used GRADE to assess certainty of evidence.

MAIN RESULTS

We included three RCTs (two double-blind and one single-blind) with 204 participants that examined the short-term effect (immediately postintervention) of memantine in autistic people. Two studies took place in the USA and the other in Iran. All three studies focused on children and adolescents, with a mean age of 9.40 (standard deviation (SD) 2.26) years. Most participants were male (range across studies 73% to 87%). The diagnosis of ASD was based on the Diagnostic and Statistical Manual of Mental Disorders (4th edition; 4th edition, text revision; or 5th edition). To confirm the diagnosis, one study used the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised (ADI-R); one used ADOS, ADI-R or the Autism Diagnostic Interview Screener; and one used the Gilliam Autism Rating Scale. Dosage of memantine was based on the child's weight and ranged from 3 mg to 15 mg per day.  Comparisons  Two studies examined memantine compared with placebo; in the other study, both groups had a behavioural intervention while only one group was given memantine.  Risk of bias All studies were rated at high risk of bias overall, as they were at high or unclear risk of bias across all but four domains in one study, and all but two domains in the other two studies. One study was funded by Forest Laboratories, LLC, (Jersey City, New Jersey), Allergan. The study sponsor was involved in the study design, data collection (via contracted clinical investigator sites), analysis and interpretation of data, and the decision to present these results. The other two studies reported no financial support or sponsorship; though in one of the two, the study medication was an in-kind contribution from Forest Pharmaceuticals. Primary outcomes There was no clear evidence of a difference between memantine and placebo with respect to severity of core symptoms of autism, although we are very uncertain about the evidence. The standardised mean difference in autism symptoms score in the intervention group versus the control group was -0.74 standard deviations (95% confidence interval (CI) -2.07 to 0.58; 2 studies, 181 participants; very low-certainty evidence; medium effect size); lower scores indicate less severe autistic symptoms. Two studies (144 participants) recorded adverse effects that the authors deemed related to the study and found there may be no difference between memantine and placebo (odds ratio (OR) 0.64, 95% CI 0.17 to 2.39; low-certainty evidence). Secondary outcomes There may be no difference between memantine and placebo on language (2 studies, 144 participants; low-certainty evidence); memory or adaptive behaviour (1 study, 23 participants; both low-certainty evidence); or hyperactivity or irritability (1 study, 121 participants; both low-certainty evidence).

AUTHORS' CONCLUSIONS

It is unclear whether memantine is an effective treatment for autistic children. None of the three included trials reported on the effectiveness of memantine in adults. Further studies using rigorous designs, larger samples, longer follow-up and clinically meaningful outcome measures that are important to autistic people and their families will strengthen our knowledge of the effects of memantine in autism.

Nonstimulant Treatments for ADHD

Nonstimulants have an important role when response or tolerability to psychostimulants is poor, when certain comorbid disorders are present, or if patients prefer nonstimulants. Here, we discuss monotherapy and combined treatment of ADHD and review mechanism of action, pharmacokinetics, efficacy, tolerability, and safety of approved, off-label, and pipeline nonstimulants. We present detailed information regarding the 4 FDA-approved nonstimulant medications-the norepinephrine reuptake inhibitors, atomoxetine and viloxazine extended release, and the α-2 adrenergic agonists, clonidine XR and guanfacine XR. We additionally review evidence regarding the off-label use of a variety of other medications. Variability across and within drug classes in nature of response, approach to titration, and temporal characteristics of treatment allow a nuanced treatment approach for individuals with comorbid disorders and complicated clinical presentations. Availability of nonstimulant medications enhances our opportunity to offer personalized treatment of ADHD across the lifespan.

Neurocognitive Outcomes from Memantine: A Pilot, Double-Blind, Placebo-Controlled Trial in Children with Autism Spectrum Disorder

Objective: Studies interrogating therapeutics which alter the excitation-inhibition balance in the treatment of autism spectrum disorder (ASD) have reported mixed results on social and behavioral outcomes. Methods: The aim of this randomized, double-blind placebo-controlled pilot trial was to evaluate neurocognitive effects of memantine over a 24-week trial. Twenty-three children ages 6-12 years old with ASD were randomized to memantine or placebo. Primary outcomes included measures of apraxia and expressive language with evaluations at midpoint (week 12) and endpoint (week 24). Secondary outcomes included memory and adaptive behavior measures. Exploratory outcomes included changes in overall cognitive functioning and behavior (e.g., Aberrant Behavior Checklist). Results: Results suggest that memantine was well-tolerated. Dropout rates were high across groups with only 14 participants completing the 6-month trial. Memantine was not associated with improvements in apraxia and expressive language. Treatment with memantine was associated with improvements in verbal recognition memory as measured by the Narrative Memory-Recognition (NEPSY-II) (F = 5.05, p = .03). In addition, exploratory analyses of changes in Intelligence quotient (IQ) suggest improvements on verbal IQ (d = 1.8). Conclusions: Results suggest future studies of memantine in ASD may benefit from shifting treatment targets from social and behavioral outcomes to exploration of effects of memantine on cognition, potentially as an adjunct to learning and educational interventions. ClinicalTrials.gov: NCT01372449.

Alcohol use disorders and ADHD

Despite a growing literature on the complex bidirectional relationship of ADHD and substance use, reviews specifically focusing on alcohol are scarce. ADHD and AUD show a significant genetic overlap, including genes involved in gluatamatergic and catecholaminergic neurotransmission. ADHD drives risky behavior and negative experiences throughout the lifespan that subsequently enhance a genetically increased risk for Alcohol Use Disorders (AUD). Impulsive decisions and a maladaptive reward system make individuals with ADHD vulnerable for alcohol use and up to 43 % develop an AUD; in adults with AUD, ADHD occurs in about 20 %, but is vastly under-recognized and under-treated. Thus, routine screening and treatment procedures need to be implemented in AUD treatment. Long-acting stimulants or non-stimulants can be used to treat ADHD in individuals with AUD. However, it is crucial to combine medical treatment for ADHD with pharmacotherapy and psychotherapy for AUD, and other comorbid disorders. Identification of individuals at risk for AUD, especially those with ADHD and conduct disorder or oppositional defiant disorder, is a key factor to prevent negative outcomes.

Emerging drugs for the treatment of attention-deficit hyperactivity disorder (ADHD)

INTRODUCTION

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder affecting up to 5.3% of children and 2.5% of adults depending on the country considered. Current pharmacological treatments for ADHD are based on stimulant or non-stimulant medications, targeting dopaminergic and noradrenergic systems in the frontal cortex and dopaminergic system in the basal ganglia. These drugs are effective and safe for the majority of patients, whereas about 20% of treated patients do not tolerate current therapies or experience insufficient efficacy. The adequate treatment of ADHD is necessary to allow a proper social placement and prevent the acquisition of additional, more severe, comorbidities.

AREAS COVERED

We conducted a review of the scientific literature and of unpublished/ongoing clinical trials to summarize the advances made in the last 10 years (2010-2020) for the pharmacological treatment of ADHD. We found many pharmacological mechanisms beyond dopaminergic and noradrenergic ones have been investigated in patients.

EXPERT OPINION

Some emerging drugs for ADHD may be promising as add-on treatment especially in children, amantadine to enhance cognitive functions and tipepidine for hyperactivity/impulsivity. Stand-alone emerging treatments for ADHD include viloxazine and dasotraline, which will soon have more clinical data available to support market access requests.

Effectiveness of a Tailored Intervention for Women With Attention Deficit Hyperactivity Disorder (ADHD) and ADHD Symptoms: A Randomized Controlled Study

IMPORTANCE

Women with attention deficit hyperactivity disorder (ADHD) and ADHD symptoms may experience difficulty carrying out desired life roles and activities.

OBJECTIVE

To determine whether a 7-wk tailored occupation-based intervention can reduce perceived stress and ADHD symptoms and enhance perceived performance of and satisfaction with daily roles and activities among women with ADHD.

DESIGN

Randomization to intervention (n = 11) and control (n = 12) groups.

SETTING

Home and community.

PARTICIPANTS

Twenty-three participants ages 20-55 yr, English speaking, and with a self-reported diagnosis of ADHD.

INTERVENTION

The intervention was administered for 7 wk in individual 1-hr sessions and addressed routine establishment, organization, time management, stress management, and sensory regulation in the home and community.

OUTCOMES AND MEASURES

Adult Attention Deficit Hyperactivity Disorder Self-Report Scale, Perceived Stress Scale, and Canadian Occupational Performance Measure.

RESULTS

At 1-wk postintervention, statistically significant differences were found between intervention and control groups in perceived stress (Z = -3.838, p < .000, d = -2.66), ADHD symptoms (Z = -3.605, p < .000, d = -2.17), and COPM Performance (Z = -4.074, p < .000, d = 3.04) and Satisfaction change scores (Z = -3.759, p < .000, d = 2.82).

CONCLUSION AND RELEVANCE

A 7-wk tailored intervention reduced perceived stress and ADHD symptoms and enhanced perceived performance of and satisfaction with desired occupational roles and activities in a sample of women with ADHD. Further research is warranted to determine whether the intervention can be useful to women with ADHD beyond the present sample.

WHAT THIS ARTICLE ADDS

This intervention may offer an effective nonpharmacological option for women with ADHD symptoms.

The Relationship Between Executive Function Deficits and DSM-5-Defined ADHD Symptoms

Objectives: To identify the relationship between the core Diagnostic and Statistical Manual of Mental Disorders (5th ed.) ADHD symptoms and executive function deficits (EFDs), to evaluate ADHD characteristics of those with executive dysfunction (ED), and to examine the predictive utility of the Adult ADHD Investigator Symptom Rating Scale (AISRS) in identifying those with adult ADHD and ED. Method: Two samples (referred and primary care practice) were pooled together for present analysis. Results: Final analysis included 297 respondents, 171 with adult ADHD. Spearman correlation coefficients and binary logistic regressions demonstrated that ADHD inattentive (IA) and hyperactive-impulsive (H-I) symptoms were moderately to strongly correlated with and highly predictive of EFDs. Receiver operating characteristic curve analysis showed that an AISRS DSM 18-item score of ⩾ 28 was most predictive of clinical ED. Conclusion: ADHD symptoms were strongly correlated with and predictive of EFDs, clinicians should screen adults with ADHD for EFDs and ADHD treatment providers should track EFD improvement in addition to DSM-5 ADHD symptoms.

Validation of the Expanded Versions of the Adult ADHD Self-Report Scale v1.1 Symptom Checklist and the Adult ADHD Investigator Symptom Rating Scale

Objective: The aim of this study is to validate the Adult ADHD Self-Report Scale (ASRS) and Adult ADHD Investigator Symptom Rating Scale (AISRS) expanded versions, including executive function deficits (EFDs) and emotional dyscontrol (EC) items, and to present ASRS and AISRS pilot normative data. Method: Two patient samples (referred and primary care physician [PCP] controls) were pooled together for these analyses. Results: Final analysis included 297 respondents, 171 with adult ADHD. Cronbach's alphas were high for all sections of the scales. Examining histograms of ASRS 31-item and AISRS 18-item total scores for ADHD controls, 95% cutoff scores were 70 and 23, respectively; histograms for pilot normative sample suggest cutoffs of 82 and 26, respectively. Conclusion: (a) ASRS- and AISRS-expanded versions have high validity in assessment of core 18 adult ADHD Diagnostic and Statistical Manual of Mental Disorders (DSM) symptoms and EFD and EC symptoms. (b) ASRS (31-item) scores 70 to 82 and AISRS (18-item) scores from 23 to 26 suggest a high likelihood of adult ADHD.

The effect of memantine in adult patients with attention deficit hyperactivity disorder

BACKGROUND

Hyperactivity disorder and attention deficit are common neurological disorders in children and adolescents. The symptoms of hyperactivity are decreased in adults, and attention deficit is more noticeable. This study was carried out to evaluate the effect of memantine on adult patients with attention deficit hyperactivity disorder (ADHD).

MATERIALS AND METHODS

In a double-blind clinical trial study, 40 patients aged 18 to 45 years with ADHD were selected on the basis on the Diagnosis and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria, and randomly assigned memantine or placebo. Before starting the treatment, Conners' screening questionnaire was completed for each patient, and the subjects were entered the study after acquiring minimum acceptable score in the questionnaire.

RESULTS

The mean age of patients who were receiving memantine and placebo was about 34.7 ± 4.48 and 31.5 ± 7.4 years, respectively. The results have shown a significant difference in the behavior and attention deficit between the two groups treated with memantine and placebo during 6 weeks (p < 0.001). Also, there was a significant difference in the third and sixth weeks between treatment groups in hyperactivity and attention deficit index (p = 0.001).

CONCLUSION

The results of this study indicated that memantine was effective in reducing symptoms of Inattention/Memory Problems, Hyperactivity/Restlessness, Impulsivity/Emotional Lability.

Hyperactivity and impulsivity in adult attention-deficit/hyperactivity disorder is related to glutamatergic dysfunction in the anterior cingulate cortex

OBJECTIVES

Attention-deficit/hyperactivity disorder (ADHD) is closely linked to the dysregulation of dopaminergic and noradrenergic neurotransmission in the fronto-striatal neural network, including the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC). Additionally, increasing evidence supports the involvement of the glutamatergic system in the pathophysiology of ADHD. Impulsivity, a core symptom in patients with ADHD, has been repeatedly associated with glutamatergic neurotransmission, and pharmacological treatment of ADHD has been shown to reduce glutamate levels in the prefrontal cortex.

METHODS

We investigated glutamate levels in the ACC and the DLPFC in 30 adults with ADHD and 30 healthy controls using single-voxel proton magnetic resonance spectroscopy on a 3T scanner.

RESULTS

The ADHD group showed a significant increase in glutamate in the ACC compared to controls, no significant differences in metabolites were observed in the DLPFC. Overall, glutamate levels in the ACC were positively correlated with ADHD symptomatology, especially hyperactivity and impulsivity symptoms.

CONCLUSIONS

Increased levels of glutamate in the ACC, which were positively correlated with hyperactivity and impulsivity, support the hypothesis that dysfunctional glutamatergic neurotransmission is at least partially responsible for ADHD symptomatology. Modulation of glutamatergic neurotransmission might therefore be a promising avenue for future pharmacological interventions.

Efficacy of Memantine as Adjunct Therapy for Autism Spectrum Disorder in Children Aged <14 Years

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a recent increase in prevalence. A timely appropriate treatment for the disorder may play a crucial role in improvements in behaviors, interactions, and communications in an individual's life. It appears that evaluation of therapeutic approaches to the patients is essential and of importance. Thus, the aim of this study was to evaluate the efficacy of memantine as adjunct therapy in children with ASD.

MATERIALS AND METHODS

This randomized single-blind clinical trial included 60 children with ASD aged <14. The children undergoing applied behavior analysis (ABA) were divided into two groups of placebo and memantine (5 mg/day: a half of tablet in the morning and a half in the evening). After a 3-month course, improvements in symptoms of ASD were evaluated in both groups based on Gilliam autism rating scale. The collected data were analyzed with SPSS (version 20) using independent samples t-test, paired samples t-test, Chi-squared test and Fisher's exact test.

RESULTS

Both groups were similar in baseline characteristics including age, gender, and ASD symptoms (P > 0.05) but post intervention, total scores of ASD symptoms in both groups of memantine (mean score1 =95.20 ± 14.49; mean score2=73.50 ± 9.81) and control group (mean scorebefore = 91.50 ± 14.35; mean scoreafter = 89.63 ± 13.95) showed a decrease which was only significant in intervention group (P < 0.001).

CONCLUSION

Accordingly, memantine administration as adjunct therapy can be more effective in improvement of ASD symptoms in children than ABA alone. Thus, it can be considered as a new selective adjunct therapy.

l-Carnosine as Adjunctive Therapy in Children and Adolescents with Attention-Deficit/Hyperactivity Disorder: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

OBJECTIVES

This study aimed to investigate the efficacy and tolerability of l-carnosine as an add-on to methylphenidate in management of children with attention-deficit/hyperactivity disorder (ADHD).

METHODS

This was an 8-week, randomized, double-blind placebo-controlled study. Fifty-six drug-free children and adolescents aged 6-17 years old with a diagnosis of ADHD entered the study. The patients were randomly assigned to l-carnosine (800 mg/d in two divided doses) or placebo plus methylphenidate (0.5-1.5 mg/kg/d) for 8 weeks. Children were assessed using the Teacher and Parent ADHD Rating Scale-IV (ADHD-RS-IV) at baseline and at weeks 4 and 8 postbaseline.

RESULTS

Fifty patients completed the study, and all had two postbaseline measurements. Using the general linear model repeated measures, significant effect was observed for time × treatment interaction on total and inattention subscales of the Parent ADHD-RS (Greenhouse-Geisser corrected: F = 3.783, df = 1.444, p = 0.041 and F = 4.032, df = 1.600, p = 0.030). Improvements in the Teacher ADHD-RS were not significantly different between the two groups in total (Greenhouse-Geisser corrected: F = 0.200, df = 1.218, p = 0.705), as well as inattention and hyperactivity subscale scores (p = 0.956 and 0.281, respectively). The frequency of side effects was not significantly different between the two treatment arms.

CONCLUSIONS

l-carnosine, as a supplementary medication, might be beneficial in treatment of children with ADHD. However, further investigations and different doses of l-carnosine are required to replicate these findings in children with ADHD.

Adolescent social defeat alters N-methyl-D-aspartic acid receptor expression and impairs fear learning in adulthood

Repeated social defeat of adolescent male rats results in adult mesocortical dopamine hypofunction, impaired working memory, and increased contextual anxiety-like behavior. Given the role of glutamate in dopamine regulation, cognition, and fear and anxiety, we investigated potential changes to N-methyl-D-aspartic acid (NMDA) receptors following adolescent social defeat. As both NMDA receptors and mesocortical dopamine are implicated in the expression and extinction of conditioned fear, a separate cohort of rats was challenged with a classical fear conditioning paradigm to investigate whether fear learning is altered by adolescent defeat. Quantitative autoradiography was used to measure 3H-MK-801 binding to NMDA receptors in regions of the medial prefrontal cortex, caudate putamen, nucleus accumbens, amygdala and hippocampus. Assessment of fear learning was achieved using an auditory fear conditioning paradigm, with freezing toward the auditory tone used as a measure of conditioned fear. Compared to controls, adolescent social defeat decreased adult NMDA receptor expression in the infralimbic region of the prefrontal cortex and central amygdala, while increasing expression in the CA3 region of the hippocampus. Previously defeated rats also displayed decreased conditioned freezing during the recall and first extinction periods, which may be related to the observed decreases and increases in NMDA receptors within the central amygdala and CA3, respectively. The alteration in NMDA receptors seen following adolescent social defeat suggests that dysfunction of glutamatergic systems, combined with mesocortical dopamine deficits, likely plays a role in the some of the long-term behavioral consequences of social stressors in adolescence seen in both preclinical and clinical studies.