Differential Roles of Key Brain Regions: Ventral Tegmental Area, Locus Coeruleus, Dorsal Raphe, Nucleus Accumbens, Caudate Nucleus, and Prefrontal Cortex in Regulating Response to Methylphenidate: Insights from Neuronal and Behavioral Studies in Freely Behaving Rats.

A total of 3102 neurons were recorded before and following acute and chronic methylphenidate (MPD) administration. Acute MPD exposure elicits mainly increases in neuronal and behavioral activity in dose-response characteristics. The response to chronic MPD exposure, as compared to acute 0.6, 2.5, or 10.0 mg/kg MPD administration, elicits electrophysiological and behavioral sensitization in some animals and electrophysiological and behavioral tolerance in others when the neuronal recording evaluations were performed based on the animals' behavioral responses, or amount of locomotor activity, to chronic MPD exposure. The majority of neurons recorded from those expressing behavioral sensitization responded to chronic MPD with further increases in firing rate as compared to the initial MPD responses. The majority of neurons recorded from animals expressing behavioral tolerance responded to chronic MPD with decreases in their firing rate as compared to the initial MPD exposures. Each of the six brain areas studied-the ventral tegmental area, locus coeruleus, dorsal raphe, nucleus accumbens, prefrontal cortex, and caudate nucleus (VTA, LC, DR, NAc, PFC, and CN)-responds significantly (p < 0.001) differently to MPD, suggesting that each one of the above brain areas exhibits different roles in the response to MPD. Moreover, this study demonstrates that it is essential to evaluate neuronal activity responses to psychostimulants based on the animals' behavioral responses to acute and chronic effects of the drug from several brain areas simultaneously to obtain accurate information on each area's role in response to the drug.

Effects of methylphenidate on mitochondrial dynamics and bioenergetics in the prefrontal cortex of juvenile rats are sex-dependent.

Methylphenidate (MPH) is a central nervous system stimulant drug and a first order prescription in the treatment of Attention Deficit Hyperactivity Disorder (ADHD). Although MPH biochemistry in neurodevelopment is not completely understood, studies showed it alters energy metabolism in rat brains. ADHD prevalence during neurodevelopment is related to males and the investigation has been mainly done in these subjects, therefore, little is known about MPH action in females and, consequently, about sexual dimorphism. In the present study we evaluated markers of mitochondrial dynamics (DRP1 and MFN2, fission and fusion, respectively), biogenesis (mtTFA) and bioenergetics (respiratory chain complexes) in prefrontal cortex of male and female juvenile rats submitted to exposure to MPH to better understand MPH effect during postnatal neurodevelopment. ATP and oxidative stress levels were also evaluated. Wistar rats received intraperitoneal injection of MPH (2.0 mg/kg) or control (saline), once a day, from 15th to 45th day of age. Results showed that MPH increased DRP1 and decreased MFN2, as well as increased mtTFA in prefrontal cortex of male rats. In female, MPH decreased NRF1 and increased Parkin, which are mitochondrial regulatory proteins. Respiratory chain complexes (complex I, SDH, complexes III and IV), ATP production and oxidative stress parameters were altered and shown to be sex-dependent. Taken together, results suggest that chronic MPH exposure at an early age in healthy animals changes mitochondrial dynamics, biogenesis and bioenergetics differently depending on the sex of the subjects.

Effects of 2 months of methylphenidate on energy expenditure in individuals with obesity: A randomized, double-blind, placebo-controlled pilot study.

Methylphenidate (MPH) has been previously shown to increase resting energy expenditure (REE) in individuals of normal weight; however, the effects on individuals living with obesity are currently unknown. Ten individuals living with obesity were randomly assigned to undergo 60 days of MPH administration with a daily dose of 0.5 mg/kg body weight or a placebo control. REE was measured before and after the 60-day intervention. There was a trend toward significance for group × time interaction on REE (p = 0.082) with a large effect size (η2 = 0.331), with MPH administration increasing REE compared to a decrease in placebo control. Preliminary findings from this pilot study show that MPH has the potential to counter the adaptive thermogenic process commonly seen in weight loss. This is a unique finding among pharmacotherapies, as no approved obesity drugs measurably impact REE.

Complex ADHD Challenging Case: Managing Co-Occurring Attention-Deficit Hyperactivity Disorder and Congenital Heart Disease with a Limited Medication Formulary: A Case from Mexico.

CASE: DL is an 8-year-old Mexican boy with a posterior atrial septal defect and partial anomalous pulmonary venous return of the right lower pulmonary vein with resultant right heart dilation with normal right ventricular systolic and diastolic function and no arrhythmias. Surgical repair was deferred, and DL's condition was being medically managed with furosemide 0.5 mg/kg BID and spironolactone 0.5 mg/kg BID.DL presents for developmental assessment due to poor performance in school following a lifting of COVID-19 pandemic restrictions and return to in-person classes. He has been attending full-time classes for 3 months without improvements in math, reading, and writing skills. Current attentional concerns at school include an inability to complete tasks without getting distracted by minimal stimuli and highly impulsive behavior.At the first assessment, DL was performing below grade expectations (e.g., reading by syllable without text comprehension, demonstrating preoperational addition and subtraction skills, inability to take dictation)-all of which was viewed as negatively impacted by attentional deficits. DL met DSM-5 criteria for ADHD, predominantly inattentive type. He was started on 10-mg immediate-release methylphenidate PO at 8 am with breakfast and a second dose of 10-mg immediate-release methylphenidate PO 4 hours after the first dose.After a month, at the first follow-up consultation, improvement in attention span, impulsivity, and school performance were observed, including reading skills and math proficiency. However, DL's mother raised concerns about circumoral cyanosis and acrocyanosis in the fingers of both hands after playing outside. These signs were not previously observed. During physical examination at the same visit, heart rate, blood pressure, and oximetry were within baseline ranges and his cardiac examination was unchanged. DL's dosage of methylphenidate was lowered to 10-mg immediate-release methylphenidate PO QD in the mornings with breakfast (8 am).DL did not return to clinic for another 2 months, having discontinued the medication after 2 months of treatment given financial limitations. His mother reported that DL's exertional circumoral cyanosis and acrocyanosis resolved while he was off medication. However, she observed an increase in inattentive symptoms and impulsivity and decline in his academic skills. She asked if our team was able continue the treatment despite the drug side effects, since she believed the benefits outweighed the disadvantages.Given these concerns, the team requested an updated cardiology assessment. The Cardiologist recommended discontinuation of methylphenidate and recommended follow-up with cardiothoracic surgery for reassessment of the surgical timeline.Given the limited treatment options in Mexico, what would you do next as the treating developmental-behavioral clinician…?

Graph analysis uncovers an opposing impact of methylphenidate on connectivity patterns within default mode network sub-divisions.

BACKGROUND: The Default Mode Network (DMN) is a central neural network, with recent evidence indicating that it is composed of functionally distinct sub-networks. Methylphenidate (MPH) administration has been shown before to modulate impulsive behavior, though it is not yet clear whether these effects relate to MPH-induced changes in DMN connectivity. To address this gap, we assessed the impact of MPH administration on functional connectivity patterns within and between distinct DMN sub-networks and tested putative relations to variability in sub-scales of impulsivity. METHODS: Fifty-five right-handed healthy adults underwent two resting-state functional MRI (rs-fMRI) scans, following acute administration of either MPH (20 mg) or placebo, via a randomized double-blind placebo-controlled design. Graph modularity analysis was implemented to fractionate the DMN into distinct sub-networks based on the impact of MPH (vs. placebo) on DMN connectivity patterns with other neural networks. RESULTS: MPH administration led to an overall decreased DMN connectivity, particularly with the auditory, cinguloopercular, and somatomotor networks, and increased connectivity with the parietomedial network. Graph analysis revealed that the DMN could be fractionated into two distinct sub-networks, with one exhibiting MPH-induced increased connectivity and the other decreased connectivity. Decreased connectivity of the DMN sub-network with the cinguloopercular network following MPH administration was associated with elevated impulsivity and non-planning impulsiveness. CONCLUSION: Current findings highlight the intricate effects of MPH administration on DMN rs-fMRI connectivity, uncovering its opposing impact on distinct DMN sub-divisions. MPH-induced dynamics in DMN connectivity patterns with other neural networks may account for some of the effects of MPH administration on impulsive behavior.

Repetitive mild traumatic brain injury impairs norepinephrine system function and psychostimulant responsivity.

Traumatic brain injury (TBI) is a complex pathophysiological process that results in a variety of neurotransmitter, behavioral, and cognitive deficits. The locus coeruleus-norepinephrine (LC-NE) system is a critical regulator of arousal levels and higher executive processes affected by TBI including attention, working memory, and decision making. LC-NE axon injury and impaired signaling within the prefrontal cortex (PFC) is a potential contributor to the neuropsychiatric symptoms after single, moderate to severe TBI. The majority of TBIs are mild, yet long-term cognitive deficits and increased susceptibility for further injury can accumulate after each repetitive mild TBI. As a potential treatment for restoring cognitive function and daytime sleepiness after injury psychostimulants, including methylphenidate (MPH) that increase levels of NE within the PFC, are being prescribed "off-label". The impact of mild and repetitive mild TBI on the LC-NE system remains limited. Therefore, we determined the extent of LC-NE and arousal dysfunction and response to therapeutic doses of MPH in rats following experimentally induced single and repetitive mild TBI. Microdialysis measures of basal NE efflux from the medial PFC and arousal measures were significantly lower after repetitive mild TBI. Females showed higher baseline PFC-NE efflux than males following single and repetitive mild TBI. In response to MPH challenge, males exhibited a blunted PFC-NE response and persistent arousal levels following repetitive mild TBI. These results provide critical insight into the role of catecholamine system dysfunction associated with cognitive deficits following repeated injury, outcome differences between sex/gender, and lack of success of MPH as an adjunctive therapy to improve cognitive function following injury.

The effects of chronic administration of stimulant and non-stimulant medications on executive functions in ADHD: A systematic review and meta-analysis.

Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with executive function deficits that are improved with medications. However, meta-analyses of stimulant effects on cognition have mostly tested single-dose effects, and there is no meta-analysis of non-stimulant effects. This systematic review and meta-analysis tested the clinically more relevant longer-term effects of Methylphenidate (20 studies; minimum 1 week) and Atomoxetine (8 studies; minimum 3 weeks) on reaction time, attention, inhibition, and working memory, searching papers on PubMed, Embase, Ovid MEDLINE, and PsycINFO. The meta-analysis of 18 studies in 1667 subjects showed that methylphenidate was superior to placebo in all cognitive domains with small to medium effect sizes (Hedges g of 0.34-0.59). The meta-analysis of atomoxetine included 7 studies in 829 subjects and showed no effects in working memory, but superior effects in the other domains with medium to large effect sizes (Hedge's g of 0.36-0.64). Meta-regression analysis showed no drug differences on cognitive effects. The meta-analyses show for the first time that chronic Methylphenidate and Atomoxetine have comparable effects of improving executive functions in people with ADHD.

The effect of methylphenidate on the dopamine and growth hormone response to exercise in children with attention-deficit hyperactivity disorder.

PURPOSE: To assess the growth hormone (GH) and Dopamine (DA) response to exercise in children with attention-deficit hyperactivity disorder (ADHD) with and without methylphenidate (MP). We hypothesized that the GH and DA response to the exercise with MP would be siginicantly lower. METHODS: Twenty children participated in the study (12 males and 8 females, age range 9-13 years). Ten with ADHD and 10 controls. Participants with ADHD performed an exercise test twice, with and without MP while controls performed one exercise test. Blood samples for GH and DA were collected before, at peak, 30 and 60 min after the end of exercise. RESULTS: Compared to controls, children with ADHD with and without MP, had a significantly lower GH (P < .002) and DA (P < .01) responses to exercise. In participants with ADHD, a significantly greater GH response (p < .04) to exercise was found when MP administered to the children before exercise, yet this response was still significantly lower than controls. CONCLUSIONS: GH and DA excretion after an exercise challenge in children with ADHD is impaired. MP slightly attenuates the GH blunted response. This may link ADHD with growth impairment in some children and explain previous findings indicating that the final adult height is usually not compromised in children with ADHD treated with MP. The combined exercise and stimulant treatment therapeutic effects needs to be further explored. TRIAL REGISTRATION NUMBER: NCT00945971.

Effects of Catecholaminergic and Transcranial Direct Current Stimulation on Response Inhibition.

BACKGROUND: The principle of gain control determines the efficiency of neuronal processing and can be enhanced with pharmacological or brain stimulation methods. It is a key factor for cognitive control, but the degree of how much gain control may be enhanced underlies a physical limit. METHODS: To investigate whether methylphenidate (MPH) and transcranial direct current stimulation (tDCS) share common underlying mechanisms and cognitive effects, we administered MPH and anodal tDCS (atDCS) over the right inferior frontal gyrus both separately and combined, while healthy adult participants (n = 104) performed a response selection and inhibition task. The recorded EEG data were analyzed with a focus on theta band activity, and source estimation analyses were conducted. RESULTS: The behavioral data show that MPH and atDCS revealed interactive effects on the ability to inhibit responses. Both MPH and atDCS modulated task-related theta oscillations in the supplementary motor area when applied separately, making a common underlying mechanism likely. When both stimulation methods were combined, there was no doubling of effects in the supplementary motor area but a shift to inferior frontal areas in the cortical network responsible for theta-driven processing. CONCLUSIONS: The results indicate that both MPH and atDCS likely share a common underlying neuronal mechanism, and interestingly, they demonstrate interactive effects when combined, which are most likely due to the physical limitations of gain control increases. The current study provides critical groundwork for future combined applications of MPH and non-invasive brain stimulation.

Interactions of catecholamines and GABA+ in cognitive control: Insights from EEG and 1H-MRS.

Catecholamines and amino acid transmitter systems are known to interact, the exact links and their impact on cognitive control functions have however remained unclear. Using a multi-modal imaging approach combining EEG and proton-magnetic resonance spectroscopy (1H-MRS), we investigated the effect of different degrees of pharmacological catecholaminergic enhancement onto theta band activity (TBA) as a measure of interference control during response inhibition and execution. It was central to our study to evaluate the predictive impact of in-vivo baseline GABA+ concentrations in the striatum, the anterior cingulate cortex (ACC) and the supplemental motor area (SMA) of healthy adults under varying degrees of methylphenidate (MPH) stimulation. We provide evidence for a predictive interrelation of baseline GABA+ concentrations in cognitive control relevant brain areas onto task-induced TBA during response control stimulated with MPH. Baseline GABA+ concentrations in the ACC, the striatum, and the SMA had a differential impact on predicting interference control-related TBA in response execution trials. GABA+ concentrations in the ACC appeared to be specifically important for TBA modulations when the cognitive effort needed for interference control was high - that is when no prior task experience exists, or in the absence of catecholaminergic enhancement with MPH. The study highlights the predictive role of baseline GABA+ concentrations in key brain areas influencing cognitive control and responsiveness to catecholaminergic enhancement, particularly in high-effort scenarios.

The effect of methylphenidate on anaesthesia recovery: An experimental study in pigs.

INTRODUCTION: Due to the lack of specific antagonists for general anaesthetics, the pharmacological stimulation of the arousal pathways might contribute to reduce recovery time. We aimed at assessing the effect of methylphenidate on physiological parameters, nociceptive withdrawal reflex thresholds, electroencephalographic variables and time of reappearance of reflexes in pigs undergoing propofol anaesthesia. MATERIALS AND METHODS: Two experiments have been performed. Five (experiment 1) and sixteen (experiment 2) healthy juvenile pigs were anaesthetised with propofol. In experiment 1, saline, methylphenidate 10 mg/kg or methylphenidate 20 mg/kg was administered intravenously at the end of propofol administration, using a cross-over design. In experiment 2, saline (n = 8) or methylphenidate 20 mg/kg (n = 8) was administered immediately after extubation. In both experiments, physiological parameters, nociceptive withdrawal reflex thresholds, electroencephalographic variables and time of reappearance of reflexes were assessed. Comparison among groups was performed using either the two-way repeated measures ANOVA followed by Bonferroni-Test or the t-test in case of parametric data, and either the Kruskal-Wallis test or the Mann-Whitney Rank Sum test in case of non-parametric data. A p value < 0.05 was considered statistically significant. RESULTS: No clinically relevant changes were observed in both experiments for physiological parameters, nociceptive withdrawal reflex thresholds and electroencephalographic variables. CONCLUSIONS: Methylphenidate does not shorten or modify anaesthesia recovery in pigs, when the sole propofol is administered.

A Post-Hoc Analysis of Emotional Lability With Delayed-Release/Extended-Release Methylphenidate in Children Aged 6 to 12 Years of Age Participating in Two Phase 3 Clinical Trials.

OBJECTIVE: DR/ER-MPH (formerly HLD200) is an evening-dosed delayed-release and extended-release methylphenidate approved for the treatment of ADHD in patients ≥6 years. Post hoc analyses of two pivotal Phase 3 trials: HLD200-107 (NCT02493777) and HLD200-108 (NCT02520388) evaluated emotional lability (EL) with DR/ER-MPH treatment. METHODS: Differences in Conners Global Index-Parent (CGI-P) EL subscale scores and age- and gender-adjusted T-scores over an open-label titration phase (HLD200-107) and between treatment and placebo groups at endpoint (HLD200-108) were evaluated. RESULTS: In HLD200-107 (N = 117) mean CGI-P EL subscale scores improved from 5.3 to 1.3 (p < .0001) after 6 weeks; in HLD200-108 significant improvements were observed in the treatment group (n = 81) versus placebo (n = 80; 3.11 vs. 4.08; p = .0053). T-scores showed an improvement with DR/ER-MPH treatment in both trials. Few emotional adverse events (AEs) were reported. CONCLUSION: DR/ER-MPH treatment resulted in statistically significant improvements in EL to the level of non-ADHD peers as contextualized by T-scores.

Effects of acute and chronic methylphenidate on prepulse inhibition: A sex difference study in Wistar rats.

BACKGROUND: The utilization of methylphenidate (MPH) is experiencing a notable surge within the adult population. This growth can be attributed to two key factors: its recreational and cognitive enhancement purposes, as well as the rising prevalence of ADHD diagnoses within this population. This study examined acute and chronic oral MPH effects on attention in male and female Wistar rats. To this end, we used a prepulse inhibition (PPI) task, which is widely used to assess psychoactive drug effects in both humans and rodents. This task allowed us to evaluate changes in attention by analyzing sensorimotor gating associated with stimulus selection process. METHODS: Animals were administered a clinically relevant dose of MPH (5 mg/kg) daily for seven days. The estrous cycle phases of the female rats were measured during behavioral sessions. The PPI task was conducted 20 min after drug administration on day 1 (acute), day 7 (chronic), and 48 h post-treatment. RESULTS: Results indicated that both acute and chronic MPH treatment impaired PPI expression in male rats, but not in female rats, regardless of their estrous cycle phase. Furthermore, a differential effect of chronic MPH treatment on the PPI task was found in male rats. Specifically, on the seventh treatment day, the PPI effect was observed when animals undertook the PPI task for the first time but was impaired in those animals in which the initial PPI session occurred under the acute influence of the drug (day 1). CONCLUSIONS: These findings suggest that the impact of MPH on sensorimotor gating responses may vary based on sex and task experience, possibly leading to state-dependent effects in healthy individuals.

AACAP Endorses the Inclusion of Methylphenidate in the WHO Model Lists of Essential Medicines.

Despite decades of clinical use and a large body of evidence, the WHO continues to exclude methylphenidate for attention-deficit/hyperactivity disorder (ADHD) from its EML.1 The exclusion of methylphenidate has dire implications for millions of individuals with ADHD worldwide, especially those living in low and low-middle income countries (LMIC), where governmental decisions to make medicines available are contingent on EML listing.

Brain connectivity changes to fast versus slow dopamine increases.

The rewarding effects of stimulant drugs such as methylphenidate (MP) depend crucially on how fast they raise dopamine in the brain. Yet how the rate of drug-induced dopamine increases impacts brain network communication remains unresolved. We manipulated route of MP administration to generate fast versus slow dopamine increases. We hypothesized that fast versus slow dopamine increases would result in a differential pattern of global brain connectivity (GBC) in association with regional levels of dopamine D1 receptors, which are critical for drug reward. Twenty healthy adults received MP intravenously (0.5 mg/kg; fast dopamine increases) and orally (60 mg; slow dopamine increases) during simultaneous [11C]raclopride PET-fMRI scans (double-blind, placebo-controlled). We tested how GBC was temporally associated with slow and fast dopamine increases on a minute-to-minute basis. Connectivity patterns were strikingly different for slow versus fast dopamine increases, and whole-brain spatial patterns were negatively correlated with one another (rho = -0.54, pspin < 0.001). GBC showed "fast>slow" associations in dorsal prefrontal cortex, insula, posterior thalamus and brainstem, caudate and precuneus; and "slow>fast" associations in ventral striatum, orbitofrontal cortex, and frontopolar cortex (pFDR < 0.05). "Fast>slow" GBC patterns showed significant spatial correspondence with D1 receptor availability (estimated via normative maps of [11C]SCH23390 binding; rho = 0.22, pspin < 0.05). Further, hippocampal GBC to fast dopamine increases was significantly negatively correlated with self-reported 'high' ratings to intravenous MP across individuals (r(19) = -0.68, pbonferroni = 0.015). Different routes of MP administration produce divergent patterns of brain connectivity. Fast dopamine increases are uniquely associated with connectivity patterns that have relevance for the subjective experience of drug reward.

Phasic dopamine signals are reduced in the spontaneously hypertensive rat and increased by methylphenidate.

The spontaneously hypertensive rat (SHR) is a selectively bred animal strain that is frequently used to model attention-deficit hyperactivity disorder (ADHD) because of certain genetically determined behavioural characteristics. To test the hypothesis that the characteristically altered response to positive reinforcement in SHRs may be due to altered phasic dopamine response to reward, we measured phasic dopamine signals in the SHRs and Sprague Dawley (SD) rats using in vivo fast-scan cyclic voltammetry. The effects of the dopamine reuptake inhibitor, methylphenidate, on these signals were also studied. Phasic dopamine signals during the pairing of a sensory cue with electrical stimulation of midbrain dopamine neurons were significantly smaller in the SHRs than in the SD rats. Over repeated pairings, the dopamine response to the sensory cue increased, whereas the response to the electrical stimulation of dopamine neurons decreased, similarly in both strains. However, the final amplitude of the response to the sensory cue after pairing was significantly smaller in SHRs than in the SD rats. Methylphenidate increased responses to sensory cues to a significantly greater extent in the SHRs than in the SD rats, due largely to differences in the low dose effect. At a higher dose, methylphenidate increased responses to sensory cues and electrical stimulation similarly in SHRs and SD rats. The smaller dopamine responses may explain the reduced salience of reward-predicting cues previously reported in the SHR, whereas the action of methylphenidate on the cue response suggests a potential mechanism for the therapeutic effects of low-dose methylphenidate in ADHD.

Neural and Cognitive Predictors of Stimulant Treatment Efficacy in Medication-Naïve ADHD Adults: A Pilot Diffusion Tensor Imaging Study.

OBJECTIVE: Stimulant medications are the main treatment for Attention Deficit Hyperactivity Disorder (ADHD), but overall treatment efficacy in adults has less than a 60% response rate. This study aimed to identify neural and cognitive markers predictive of longitudinal improvement in response to stimulant treatment in drug-naïve adults with ADHD. METHOD: We used diffusion tensor imaging (DTI) and executive function measures with 36 drug-naïve adult ADHD patients in a prospective study design. RESULTS: Structural connectivity (measured by fractional anisotropy, FA) in striatal regions correlated with ADHD clinical symptom improvement following stimulant treatment (amphetamine or methylphenidate) in better medication responders. A significant positive correlation was also found between working memory performance and stimulant-related symptom improvement. Higher pre-treatment working memory scores correlated with greater response. CONCLUSION: These findings provide evidence of pre-treatment neural and behavioral markers predictive of longitudinal treatment response to stimulant medications in adults with ADHD.

Sensorimotor dysfunction due to developmental manganese exposure is less severe in adult female than male rats and partially improved by acute methylphenidate treatment.

Epidemiological studies have reported associations between elevated manganese (Mn) exposure and poorer psychomotor performance in children. Our studies in adult male rats have established that this relationship is causal and that prolonged methylphenidate (MPH) treatment is efficacious in treating this area of dysfunction. However, it is unclear if sensitivity to these Mn deficits differs between females and males, and whether existing pharmacological therapies are efficacious in improving sensorimotor dysfunction in females. To address these questions, we used our rat model of childhood environmental Mn exposure and the Montoya staircase test to determine whether 1) there are sex differences in the lasting sensorimotor dysfunction caused by developmental Mn exposure, and 2) MPH treatment is efficacious in ameliorating the sensorimotor deficits in females. Female and male neonates were treated orally with Mn (50 mg Mn/kg/d) from postnatal day 1 to 21 and evaluated for skilled forelimb sensorimotor performance as adults. Subsequently, the efficacy of acute oral MPH treatment (doses of 0, 0.5, and 3.0 mg MPH/kg/d) was assessed in females using a within-subject MPH treatment design. Developmental postnatal Mn exposure produced lasting sensorimotor reaching and grasping deficits that were milder in females than in males. Acute MPH treatment of Mn-exposed females with the 0.5 mg/kg/d dose attenuated the reaching dysfunction without alleviating grasping dysfunction. These findings show sex-based variations in sensitivity to the sensorimotor impairment caused by developmental Mn exposure, and they are consistent with prior studies showing less vulnerability of females to Mn-induced dysfunction in other functional domains, possibly due to the protective effects of estrogen. Given our previous work showing the efficacy of MPH treatment to alleviate Mn-induced inattention, impulsiveness, and sensorimotor dysfunctions in adult male rats, they also highlight the need for further research into sex-based differences in cognitive and behavioral areas of brain function, and the efficacy of therapeutics in treating behavioral dysfunction in females. Supported by NIEHS R01ES028369.

Long-term medication for ADHD (LMA) trial: 2-year prospective observational study in children and adolescents. Core symptoms, daily functioning, and comorbidity outcomes.

More knowledge is needed about long-term ADHD medication and symptom, daily functioning, comorbidity, and tolerability outcomes. This "Long-term Medication for ADHD (LMA) trial" was a prospective observational 2-year trial in children and adolescents aged 6-18 years (extension of 1-year trial). Participants met criteria for DSM-5 ADHD (inattentive or combined), with complex comorbidities; autism spectrum disorder (31%), autistic traits (24%), oppositional symptoms (59%), anxiety (32%), dyslexia/language disorder (16%), borderline intellectual functioning (17%). Medication was individually tailored and followed-up at clinical visits (1, 2, 3, 6, 12, 18, 24 months). Primary outcome: Clinical Global Impression-Severity and Improvement scales (CGI-S, CGI-I). Secondary outcomes: Investigator-rated ADHD-Rating Scale, Weiss Functional Impairment Rating Scale-Parent report (WFIRS-P; Family, School Learning and Behavior, Life Skills, Self-Concept, Social Activities, and Risky Activities domains), comorbidity symptoms and adverse events (AEs). One hundred twenty-eight participants were enrolled (1-year trial only n = 27, LMA trial n = 101). Of these 29 (23%) discontinued, mainly due to AEs (n = 7), moving (n = 7), or no longer needing medication (n = 6). Main AEs were poor appetite, low mood, anxiety, irritability, fatigue. Improvements from baseline to 2 years were large in CGI-S (effect size (ES) 2.28), ADHD-RS (ES 2.06), and moderate to large in WFIRS-P (ES total 0.73, learning 0.4, family 0.67). Overall, the trial showed robust and sustained improvements in ADHD symptom severity and daily functioning over a period of 2 years of ADHD medication in children and adolescents with ADHD and complex comorbidities. Most AEs were mild. Comorbidity symptoms were improved after 1 year, particularly oppositional symptoms, depression, and anxiety.

Development of a novel rodent rapid serial visual presentation task reveals dissociable effects of stimulant versus nonstimulant treatments on attentional processes.

The rapid serial visual presentation (RSVP) task and continuous performance tasks (CPT) are used to assess attentional impairments in patients with psychiatric and neurological conditions. This study developed a novel touchscreen task for rats based on the structure of a human RSVP task and used pharmacological manipulations to investigate their effects on different performance measures. Normal animals were trained to respond to a target image and withhold responding to distractor images presented within a continuous sequence. In a second version of the task, a false-alarm image was included, so performance could be assessed relative to two types of nontarget distractors. The effects of acute administration of stimulant and nonstimulant treatments for ADHD (amphetamine and atomoxetine) were tested in both tasks. Methylphenidate, ketamine, and nicotine were tested in the first task only. Amphetamine made animals more impulsive and decreased overall accuracy but increased accuracy when the target was presented early in the image sequence. Atomoxetine improved accuracy overall with a specific reduction in false-alarm responses and a shift in the attentional curve reflecting improved accuracy for targets later in the image sequence. However, atomoxetine also slowed responding and increased omissions. Ketamine, nicotine, and methylphenidate had no specific effects at the doses tested. These results suggest that stimulant versus nonstimulant treatments have different effects on attention and impulsive behaviour in this rat version of an RSVP task. These results also suggest that RSVP-like tasks have the potential to be used to study attention in rodents.