Neuropharmacological mechanisms underlying the neuroprotective effects of methylphenidate

Protective effects of amphetamine and methylphenidate against dopaminergic neurotoxicants in SH-SY5Y cells

Full treatment of the second most common neurodegenerative disorder, Parkinson's disease (PD), is still considered an unmet need. As the psychostimulants, amphetamine (AMPH) and methylphenidate (MPH), were shown to be neuroprotective against stroke and other neuronal injury diseases, this study aimed to evaluate their neuroprotective potential against two dopaminergic neurotoxicants, 6-hydroxydopamine (6-OHDA) and paraquat (PQ), in differentiated human dopaminergic SH-SY5Y cells. Neither cytotoxicity nor mitochondrial membrane potential changes were seen following a 24-hour exposure to either therapeutic concentration of AMPH or MPH (0.001-10 μM). On the other hand, a 24-hour exposure to 6-OHDA (31.25-500 μM) or PQ (100-5000 μM) induced concentration-dependent mitochondrial dysfunction, assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and lysosomal damage, evaluated by the neutral red uptake assay. The lethal concentrations 25 and 50 retrieved from the concentration-toxicity curves in the MTT assay were 99.9 µM and 133.6 µM for 6-OHDA, or 422 µM and 585.8 µM for PQ. Both toxicants caused mitochondrial membrane potential depolarization, but only 6-OHDA increased reactive oxygen species (ROS). Most importantly, PQ-induced toxicity was partially prevented by 1 μM of AMPH or MPH. Nonetheless, neither AMPH nor MPH could prevent 6-OHDA toxicity in this experimental model. According to these findings, AMPH and MPH may provide some neuroprotection against PQ-induced neurotoxicity, but further investigation is required to determine the exact mechanism underlying this protection.

Chronic Methylphenidate Effects on Brain Gene Expression: An Exploratory Review

Methylphenidate (MP) is a psychostimulant commonly prescribed for individuals with attention deficit hyperactivity disorder (ADHD) but it is also taken with and without a prescription for performance enhancement. Prior research has characterized the effects of MP on behavior, cognition, and neurochemistry. This exploratory review covers the uses of MP and examined the effects of MP on gene expression in the brain following exposure. Overall, MP causes a wide-spread potentiation of genes, in a region-specific manner; consequently, inducing neuronal alterations, such as synaptic plasticity and transmission, resulting in observed behaviors and affects. Monoamine neurotransmitters and post-synaptic density protein genes generally had a potentiating effect in gene expression after exposure to MP.

Attention deficits as a key player in the symptomatology of posttraumatic stress disorder: A review

Posttraumatic stress disorder (PTSD) is a debilitating psychiatric disorder characterized by symptoms such as re-experiencing of the psychotrauma and hyperarousal. Although current literature mainly discusses the emotionally related aspects of these symptoms, studies also highlight the relation between re-experiencing, hyperarousability, and attention deficits, which are associated with poorer daily function and reduced quality of life. This review provides a comprehensive analysis of the existing research on attention deficits among adults with PTSD. A systematic search through five databases resulted in the inclusion of 48 peer-reviewed, English-language articles, describing 49 distinct studies. Using a total of 47 different attentional assessment tools, the majority of studies investigated sustained (n = 40), divided (n = 16), or selective (n = 14) attention. A total of 30 studies (61.2%) found significant correlations between PTSD symptoms and attention deficits, and 10 studies (20.4%) found that higher levels of attention deficits were predictive of worse PTSD symptoms. Moreover, neuroimaging results of six (f)MRI and three EEG studies identified various potential neurobiological pathways involved, including (pre)frontal attention networks. Together, the body of research shows that attention deficits in individuals with PTSD are common and occur in surroundings with emotionally neutral stimuli. Nonetheless, current treatment strategies do not target these attentional difficulties. We propose a novel perspective to PTSD diagnosis and treatment strategies based on attention deficits and their relation with top-down regulation of re-experiencing and subsequent other PTSD symptoms.

Psychostimulants for the Treatment of Comorbid Post-traumatic Stress Disorder (PTSD) in a Patient With Attention-Deficit/Hyperactivity Disorder (ADHD): A Case Report and Literature Summary

We present a case of a 35-year-old female with an extensive history of attention-deficit/hyperactivity disorder (ADHD) who experienced a traumatic sexual and physical assault and later developed post-traumatic stress disorder (PTSD). The patient disclosed that her current medication (Vyvanse) used to treat ADHD has been the only treatment modality that has helped control her intrusive thoughts and nightmares. Decreased dopaminergic receptors are associated with developing PTSD and psychostimulants are known to have an effect of increasing Dopamine release. This case report shows promising results and potential off-label use of psychostimulants for the treatment of PTSD. 

Thiols and ceruloplasmin levels in serum of children with attention deficit hyperactivity disorder: A cross-sectional study

Attention deficit hyperactivity disorder (ADHD) is a childhood onset disorder with well-known findings that include impulsivity, hyperactivity, and inattention. This study aims to explore the relationship between the levels of ceruloplasmin, native thiol, total thiol, and disulfide and ADHD by comparing case and control groups. The study case group comprised 50 children aged 6-16 years who had been diagnosed with ADHD. The control group included 47 healthy children. Clinical interviews were conducted and the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version Turkish Adaptation and the Conners Parent Rating Scale were administered. Additionally, blood samples were taken and native thiol, total thiol, disulfide, and ceruloplasmin levels measured. In the ADHD group, the mean native thiol, total thiol, and disulfide levels were significantly lower than the control group. There was no significant difference between the ADHD and control groups in ceruloplasmin levels. Total thiol and native thiol levels were inversely correlated with scores on the Conners Inattention and Hyperactivity subscales; total thiol was negatively correlated with the ADHD index. Thiol-disulfide homeostasis was impaired in ADHD children and was related to symptom severity. Oxidative stress balance may play a role in ADHD.

Methylphenidate and alcohol effects on flash-evoked potentials, body temperature, and behavior in Long-Evans rats

Methylphenidate (MPD) is a psychostimulant used to treat attention deficit hyperactivity disorder (ADHD). Most adult ADHD patients use ethanol in combination with MPD. This research examined the effects of MPD and ethanol on flash-evoked potentials (FEPs; cortical responses frequently used to assess neural activity and sensory processing) recorded from the visual cortex (VC) and superior colliculus (SC; a structure involved in attention and orientation) of chronically implanted male Long-Evans rats, and on body temperature and open field behavior. For one group of rats, either saline or ethanol (2.0 g/kg) was given 5 min prior to either saline or MPD (2.9 mg/kg). FEPs were recorded 10 and 20 min later. In the VC, ethanol decreased amplitudes of several components, but increased P2. MPD increased N3, but decreased P3 and P4. Ethanol increased the latency of several components. In the SC, ethanol decreased all three components, while MPD increased P3. Ethanol increased latency of all components. During FEP testing, ethanol decreased body movement while MPD increased movement. In the open field, line crossings were increased but rearings were decreased by ethanol. Both ethanol and MPD produced hypothermia. A second group of rats was given MPD at 11.6 mg/kg. Ethanol decreased several VC amplitudes, but increased P2. MPD increased N3 amplitude but decreased amplitude for other components. MPD also counteracted the effect of ethanol on the amplitude of P2 and N3. Both ethanol and MPD increased the latency of several components. In the SC, ethanol decreased all component amplitudes, while MPD increased P3 but decreased N4. Ethanol increased all component latencies, while MPD increased latency for two components. During FEP testing, ethanol decreased body movement while MPD increased movement. In the open field, line crossings were increased by ethanol and MPD. Rearings were eliminated by ethanol in the open field but increased by MPD, and MPD counteracted the effect of ethanol on rearings. Both ethanol and MPD produced hypothermia. Some of these results might help explain why users take MPD and ethanol in combination in order to enable consuming larger amounts of alcohol.

A haplotype of the dopamine transporter gene modulates regional homogeneity, gray matter volume, and visual memory in children with attention-deficit/hyperactivity disorder

BACKGROUND

The dopamine transporter gene (DAT1) and visual memory deficits have been consistently reported to be associated with attention-deficit/hyperactivity disorder (ADHD). This study aimed to examine whether a DAT1 haplotype affected functional and structural brain alterations in children with ADHD and whether those alterations were associated with visual memory.

METHOD

We recruited a total of 37 drug-naïve children with ADHD (17 with the DAT1 rs27048 (C)/rs429699 (T) haplotype and 20 without the CT haplotype) and 37 typically developing children (17 with the CT haplotype and 20 without the CT haplotype). Visual memory was assessed by the pattern recognition memory (PRM) and spatial recognition memory (SRM) tasks. We analyzed functional and structural brain architecture with regional homogeneity (ReHo) and gray matter volume (GMV).

RESULTS

The CT haplotype was associated with decreased ReHo in the left superior occipital gyrus, cuneus, and precuneus; and decreased GMV in the left superior occipital gyrus, cuneus, and precuneus, and in the right angular gyrus. Significant interactions of ADHD and the CT haplotype were found in the right postcentral gyrus for ReHo and in the right supplementary motor area for GMV. For the ADHD-CT group, we found negative correlations of total correct responses in PRM and SRM and positive correlations of mean latency of correct responses in PRM with the GMV in the left superior occipital gyrus, cuneus, and precuneus.

CONCLUSIONS

Our findings suggest that the DAT1-related GMV alterations in the posterior cortical regions may contribute to visual memory performance in children with ADHD.

Rationale for Dietary Antioxidant Treatment of ADHD

Increasing understanding arises regarding disadvantages of stimulant medication in children with ADHD (Attention-Deficit Hyperactivity Disorder). This review presents scientific findings supporting dietary antioxidant treatment of ADHD and describes substantial alterations in the immune system, epigenetic regulation of gene expression, and oxidative stress regulation in ADHD. As a result, chronic inflammation and oxidative stress could develop, which can lead to ADHD symptoms, for example by chronic T-cell-mediated neuroinflammation, as well as by neuronal oxidative damage and loss of normal cerebral functions. Therefore, modulation of immune system activity and oxidant-antioxidant balance using nutritional approaches might have potential in ADHD treatment. The use of natural antioxidants against oxidative conditions is an emerging field in the management of neurodegenerative diseases. Dietary polyphenols, for example, have antioxidant capacities as well as immunoregulatory effects and, therefore, appear appropriate in ADHD therapy. This review can stimulate the development and investigation of dietary antioxidant treatment in ADHD, which is highly desired.

Methylphenidate clinically oral doses improved brain and heart glutathione redox status and evoked renal and cardiac tissue injury in rats

Methylphenidate (MPH) is a first-line stimulant drug to treat attention deficit hyperactivity disorder (ADHD). Overdiagnosis of ADHD and MPH abuse lead to serious concerns about the possible long-term adverse consequences of MPH in healthy children and adolescents. We aimed to evaluate MPH effects in adolescent male Wistar rats (postnatal day 40) using an oral dose scheme (2 daily MPH doses 5 mg/kg in a 5% sucrose solution, 5 h apart, for 7 days) that mimics the therapeutic doses given to human adolescents. Twenty-four hours after the last MPH administration, rats were sacrificed and brain areas [cerebellum, prefrontal cortex (PFC), hippocampus, and striatum], peripheral organs (liver, heart, and kidneys), and blood were collected for biochemical and histological analysis. MPH treatment did not alter rats' body temperature or weight, neither food or water intake throughout the experiment. The ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) significantly increased in the PFC and hippocampus of MPH-treated rats, meanwhile protein carbonylation remained unchanged in the brain. In the heart, the GSH/GSSG ratio and GSH levels were significantly increased, with decreased GSSG, while histology revealed significant damage, namely interstitial edema, vascular congestion, and presence of a fibrin-like material in the interstitial space. In the kidneys, MPH treatment resulted in extensive necrotic areas with cellular disorganization and cell infiltration, and immunohistochemistry analysis revealed a marked activation of nuclear factor-ĸB. This study showed that clinically relevant oral MPH doses improve the GSH redox status in the brain and heart, but evoke heart and kidney tissue damage to adolescent rats.

Methylphenidate effects in the young brain: friend or foe?

Attention deficit hyperactivity disorder (ADHD) is one of the most prevalent neuropsychiatry disorders in children and adolescents, and methylphenidate (MPH) is a first-line stimulant drug available worldwide for its treatment. Despite the proven therapeutic efficacy, concerns have been raised regarding the possible consequences of chronic MPH exposure during childhood and adolescence. Disturbances in the neurodevelopment at these crucial stages are major concerns given the unknown future life consequences. This review is focused on the long-term adverse effects of MPH to the brain biochemistry. Reports conducted with young and/or adolescent animals and studies with humans are reviewed in the context of long-term consequences after early life-exposure. MPH pharmacokinetics is also reviewed as there are differences among laboratory animals and humans that may be relevant to extrapolate the findings. Studies reveal that exposure to MPH in laboratory animals during young and/or adolescent ages can impact the brain, but the outcomes are dependent on MPH dose, treatment period, and animal's age. Importantly, the female sex is largely overlooked in both animal and human studies. Unfortunately, human reports that evaluate adults following adolescent or child exposure to MPH are very scarce. In general, human data indicates that MPH is generally safe, although it can promote several brain changes in early ages. Even so, there is a lack of long course patient evaluation to clearly establish whether MPH-induced changes are friendly or foe to the brain and more human studies are needed to assess the adult brain changes that arise from early MPH treatment.

ADHD-associated dopamine transporter, latrophilin and neurofibromin share a dopamine-related locomotor signature in Drosophila

Attention-deficit/hyperactivity disorder (ADHD) is a common, highly heritable neuropsychiatric disorder with hyperactivity as one of the hallmarks. Aberrant dopamine signaling is thought to be a major theme in ADHD, but how this relates to the vast majority of ADHD candidate genes is illusive. Here we report a Drosophila dopamine-related locomotor endophenotype that is shared by pan-neuronal knockdown of orthologs of the ADHD-associated genes Dopamine transporter (DAT1) and Latrophilin (LPHN3), and of a gene causing a monogenic disorder with frequent ADHD comorbidity: Neurofibromin (NF1). The locomotor signature was not found in control models and could be ameliorated by methylphenidate, validating its relevance to symptoms of the disorder. The Drosophila ADHD endophenotype can be further exploited in high throughput to characterize the growing number of candidate genes. It represents an equally useful outcome measure for testing chemical compounds to define novel treatment options.

Catecholaminergic based therapies for functional recovery after TBI

Among the many pathophysiologic consequences of traumatic brain injury are changes in catecholamines, including dopamine, epinephrine, and norepinephrine. In the context of TBI, dopamine is the one most extensively studied, though some research exploring epinephrine and norepinephrine have also been published. The purpose of this review is to summarize the evidence surrounding use of drugs that target the catecholaminergic system on pathophysiological and functional outcomes of TBI using published evidence from pre-clinical and clinical brain injury studies. Evidence of the effects of specific drugs that target catecholamines as agonists or antagonists will be discussed. Taken together, available evidence suggests that therapies targeting the catecholaminergic system may attenuate functional deficits after TBI. Notably, it is fairly common for TBI patients to be treated with catecholamine agonists for either physiological symptoms of TBI (e.g. altered cerebral perfusion pressures) or a co-occuring condition (e.g. shock), or cognitive symptoms (e.g. attentional and arousal deficits). Previous clinical trials are limited by methodological limitations, failure to replicate findings, challenges translating therapies to clinical practice, the complexity or lack of specificity of catecholamine receptors, as well as potentially counfounding effects of personal and genetic factors. Overall, there is a need for additional research evidence, along with a need for systematic dissemination of important study details and results as outlined in the common data elements published by the National Institute of Neurological Diseases and Stroke. Ultimately, a better understanding of catecholamines in the context of TBI may lead to therapeutic advancements. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Oxidative Stress and ADHD: A Meta-Analysis

OBJECTIVE

To clarify the role of oxidative stress and antioxidant activity in ADHD.

METHOD

We examined the association of ADHD and oxidative stress by applying random effects meta-analysis to studies of oxidative stress and antioxidant status in medication naive patients with ADHD and controls.

RESULTS

Six studies of a total of 231 ADHD patients and 207 controls met our selection criteria. The association between ADHD and antioxidant status was not significant. We found a significant association between ADHD and oxidative stress that could not be accounted for by publication bias. The significant association lost significance after correcting for intrastudy clustering. No one observation accounted for the positive result.

CONCLUSION

These results are preliminary given the small number of studies. They suggest that patients with ADHD have normal levels of antioxidant production, but that their response to oxidative stress is insufficient, leading to oxidative damage.

Methylphenidate and desipramine combined treatment improves PTSD symptomatology in a rat model

Antidepressant medication constitutes the first line pharmacological treatment for posttraumatic stress disorder (PTSD), however, because many patients display no beneficial drug effects it has been suggested that combinations of antidepressants with additional drugs may be necessary. The defining symptoms of PTSD include re-experiencing, avoidance and hyperarousal. In addition, PTSD patients were shown to become easily distracted and often suffer from poor concentration together with indications of comorbidity with attention-deficit hyperactivity disorder (ADHD). Methylphenidate (MPH) is the most common and effective drug treatment for ADHD, thus we aimed to investigate the effects of MPH treatment, by itself or in combination with the antidepressants fluoxetine (FLU) or desipramine (DES). We modified an animal model of PTSD by exposing rats to chronic stress and evaluating the subsequent development of behavioral PTSD-like symptoms, as well as the effects on proinflammatory cytokines, which were implicated in PTSD. We report that while FLU or DES had a beneficial effect on avoidance and hyperarousal symptoms, MPH improved all three symptoms. Moreover, the combination of MPH with DES produced the most dramatic beneficial effects. Serum levels of interleukin-1β (IL-1β) and IL-6 were elevated in the PTSD-like group compared with the control group, and were decreased by MPH, FLU, DES or the combination drug treatments, with the combination of DES+MPH producing the most complete rescue of the inflammatory response. Considering the versatile symptoms of PTSD, our results suggest a new combined treatment for PTSD comprising the antidepressant DES and the psychostimulant MPH.

Coping strategies and interventions for cognitive changes in patients with cancer

OBJECTIVES

To provide a comprehensive summary of the coping strategies and evidence-based interventions used to address cognitive impairment following cancer and cancer treatment.

DATA SOURCES

Review and synthesis of empirical articles.

CONCLUSION

Survivors identified a structured environment and validation of their cognitive concerns as essential to adjustment. Although interventional research is still limited, non-pharmacological approaches such as cognitive training programs show the greatest promise.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses must understand the available evidence and provide information and guidance to cancer survivors to address cognitive changes after cancer.

Acute administration of methylphenidate alters the prefrontal cortex neuronal activity in a dose-response characteristic

The prefrontal cortex (PFC) is part of the collective structures known as the motive circuit. The PFC acts to enhance higher cognitive functions as well as mediate the effects of psychostimulants. Previous literature shows the importance of PFC neuronal adaptation in response to acute and chronic psychostimulant exposure. The PFC receives input from other motive circuit structures, including the ventral tegmental area, which mediates and facilitates the rewarding effects of psychostimulant exposure. PFC neuronal and locomotor activity from freely behaving rats previously implanted with permanent semimicroelectrodes were recorded concomitantly using a telemetric (wireless) recording system. Methylphenidate (MPD) is used as a leading treatment for behavioral disorders and more recently as a cognitive enhancer. Therefore, the property of MPD dose response on PFC neuronal activity was investigated. The results indicate that MPD modulates PFC neuronal activity and behavioral activity in a dose-dependent manner. PFC neuronal responses to 0.6 mg/kg elicited mainly a decrease in PFC neuronal activity, while higher MPD doses (2.5 and 10.0 mg/kg) elicited mainly increased neuronal activity in response to MPD. The correlation between MPD effects on PFC neuronal activity and animal behavior is discussed.

The effect of systemic chemotherapy on neurogenesis, plasticity and memory

Chemotherapy has been enormously successful in treating many forms of cancer and improving patient survival rates. With the increasing numbers of survivors, a number of cognitive side effects have become apparent. These have been called "chemobrain" or "chemofog" among patient groups, who describe the symptoms as a decline in memory, concentration and executive functions. Changes which, although subtle, can cause significant distress among patients and prevent a return to the quality of life experienced before treatment. This cognitive side effect of chemotherapy was not anticipated as it had been assumed that chemotherapy agents, administered systematically, could not cross the blood-brain barrier and that the brain was therefore protected from their action. It is now realised that low concentrations of many chemotherapy agents cross the blood-brain barrier and even those that are completely prevented from doing so, can induce the production of inflammatory cytokines in peripheral tissues which in turn can cross the blood-brain barrier and impact on the brain. A large number of patient studies have shown that cognitive decline is found in a proportion of patients treated with a variety of chemotherapy agents for different types of cancer. The deficits experienced by these patients can last for up to several years and have a deleterious effect on educational attainment and ability to return to work. Imaging studies of patients after systemic chemotherapy show that this treatment produces structural and functional changes in the brain some of which seem to persist even when the cognitive deficits have ceased. This suggests that, with time, brain plasticity may be able to compensate for the deleterious effects of chemotherapy treatment. A number of mechanisms have been suggested for the changes in brain structure and function found after chemotherapy. These include both central and peripheral inflammatory changes, demyelination of white matter tracts, a reduction in stem cell proliferation in both the hippocampal neurogenic region and by oligodendrocyte precursors as well as changes in hormonal or growth factor levels. A number of possible treatments have been suggested which range from pharmacological interventions to cognitive behavioural therapies. Some of these have only been tested in animal models while others have produced varying degrees of improvement in patient populations. Currently, there is no recognised treatment and a greater understanding of the causes of the cognitive decline experienced after chemotherapy will be key to finding ways of preventing or treating the effects of chemobrain.

Nomifensine alters sex differences in striatal dopaminergic function

A series of three experiments are presented in which the acute effects of the catecholamine reuptake inhibitor, nomifensine, upon striatal dopaminergic function are compared in female and male mice. In Experiment 1, treatment with nomifensine (5 mg kg⁻¹), at 30 min prior to injection of methamphetamine (40 mg kg⁻¹) significantly decreased the amount of striatal dopamine depletion in male, but not female, mice, thereby abolishing the sex difference in methamphetamine-induced neurotoxicity (males > females). In Experiment 2, the methamphetamine-evoked sex differences in dopamine and DOPAC output from superfused striatal tissue (males > females) were abolished in mice treated with nomifensine at 30 min prior to tissue removal. In Experiment 3, the potassium chloride-evoked sex differences in dopamine and DOPAC output from superfused striatal tissue (females > males) were reversed in mice treated with nomifensine at 30 min prior to tissue removal. Taken together these results demonstrate the critical role played by catecholamine transporters in sex differences of dopaminergic function and suggest that this may involve the dopamine transporter, due to its high concentrations within the striatum. Such findings highlight the need for gender-specific considerations in use of treatments that target reuptake transporters function.

Effects of long-acting methylphenidate in adults with attention deficit hyperactivity disorder: a study with paired-pulse transcranial magnetic stimulation

BACKGROUND

Methylphenidate improves attention deficits, hyperactivity and impulsivity in attention deficit hyperactivity disorder (ADHD). Recent investigations into motor cortex excitability with paired-pulse transcranial magnetic stimulation (ppTMS) technique have shown inhibition deficits in ADHD which correlate with clinical symptomatology. Therefore, we investigated the neurophysiological effects of long-acting methylphenidate (LA-Mph) with the ppTMS technique in adult patients with ADHD.

METHODS

Thirteen right-handed adult ADHD patients who were first diagnosed with ADHD were included in this ppTMS study. Measurements took place before and during treatment with LA-Mph (30-54 mg/day). Statistical analyses were performed to investigate treatment effects and correlations with clinical symptomatology.

RESULTS

LA-Mph significantly decreased the relative short intracortical motor inhibition (SICI) magnetically evoked potential (MEP) amplitude at 3-ms interstimulus interval (conditioned/unconditioned MEP amplitude: 0.83 ± 0.76 drug-free vs. 0.29 ± 0.19 with LA-Mph; p=0.020). The relative intracortical facilitation MEP amplitude at 11 ms interstimulus interval (conditioned/unconditioned MEP amplitude: 1.51 ± 0.92 drug-free vs. 1.79 ± 0.95 with LA-Mph) was not significantly increased. The reduced relative SICI MEP amplitude with LA-Mph correlated significantly with the improvement of the psychopathological ADHD self-rating total scores (p=0.046).

CONCLUSION

These results show that in adult patients with ADHD, LA-Mph significantly improves motor disinhibition and might have differential stabilizing effects on motor hyperexcitability.

Psychostimulant treatment of combat-related posttraumatic stress disorder

The objective of this paper is to describe three cases of combat-related posttraumatic stress disorder (PTSD), largely refractory to standard medication treatment who responded well to psychostimulant treatment. Symptoms of PTSD potentially result from chronic, stress-induced dopaminergic dysfunction in the prefrontal cortex/basal ganglia system. Psychostimulants, by their relative propensity to enhance dopamine (DA) activity within these brain regions, may have particular value in targeting this dysfunction. Evidence of dopaminergic dysfunction following chronic stress is reviewed and possible mechanism of action of psychostimulants is explored. Psychostimulants appeared to be well tolerated and beneficial in the treatment of the cases of combat-related PTSD reported. General applicability of the use of psychostimulants in combat- and non-combat-related PTSD awaits further study. The potential implications of these findings in further delineating pathophysiology and treatment in PTSD deserve further exploration.

Chemotherapy and cognitive impairment: treatment options

Chemotherapy has improved survival rates in patients with many of the common cancers. However, there is reliable evidence that, as a result of treatment, a subset of cancer survivors experience cognitive problems that can last for many years after the completion of chemotherapy. The etiology of this phenomenon is largely unknown, and currently there are no proven treatments. This article explores the clinical and preclinical literature on potential therapies for chemotherapy-induced cognitive impairments. Emerging results suggest that both pharmacological and behavioral approaches may offer patients some benefits. However, research in this area has been limited and is sometimes fraught with methodological flaws. As a result, it is difficult to draw definite conclusions regarding treatment efficacy. These issues, along with predictors of cognitive decline, are discussed in the light of possible interventions.

Association between the dopamine transporter gene and the inattentive subtype of attention deficit hyperactivity disorder in Taiwan

Attention deficit hyperactivity disorder (ADHD) is a common heritable childhood psychiatric disorder. Since methylphenidate, one of the main drugs used to treat ADHD, targets the dopamine transporter, this study examined the linkage disequilibrium (LD) structure of the dopamine transporter gene (DAT1) and investigated whether the DAT1 gene was associated with ADHD. This Chinese family-based association sample consisted of 273 DSM-IV diagnosed ADHD probands and their family members (n=906). We screened 15 polymorphisms across the DAT1 gene, including 14 single nucleotide polymorphism (SNP) markers and the variable number of tandem repeat (VNTR) polymorphism in 3'-untranslated region (3'UTR). Calculations of pairwise LD revealed three main haplotype blocks (HBs): HB1 (intron 2 through intron 6), HB2 (intron 8 through intron 11), and HB3 (3'UTR). Family-Based Association Tests showed that no allele was significantly more transmitted than expected to the ADHD children for these 15 markers. Haplotype-Based Association Tests showed that a haplotype rs27048 (C)/rs429699 (T) was significantly associated with the inattentive subtype (P=0.008). In quantitative analyses, this haplotype also demonstrated significant association with the inattention severity (P=0.012). Our finding of the haplotype rs27048 (C)/rs429699 (T) as a novel genetic marker in the inattentive ADHD subtype suggests that variation in the DAT1 gene may primarily affect the inattentive subtype of ADHD.