Methylphenidate Dose-Dependently Affects Aggression and Improves Fear Extinction and Anxiety in BALB/cJ Mice

Psychostimulants and social behaviors

Mounting evidence from animal models and human studies indicates that psychostimulants can significantly affect social behaviors. This is not surprising considering that the neural circuits underlying the regulation and expression of social behaviors are highly overlapped with those targeted by psychostimulants, which in most cases have strong rewarding and, consequently, addictive properties. In the present work, we provide an overview regarding the effects of illicit and prescription psychostimulants, such as cocaine, amphetamine-type stimulants, methylphenidate or modafinil, upon social behaviors such as social play, maternal behavior, aggression, pair bonding and social cognition and how psychostimulants in both animals and humans alter them. Finally, we discuss why these effects can vary depending on numerous variables such as the type of drug considered, acute versus long-term use, clinical versus recreational consumption, or the presence or absence of concomitant risk factors.

Effects of the interaction between PTSD and ADHD symptoms on the level of reporting psychotic-like experiences: findings from a non-clinical population

Objective

Psychotic-like experiences (PLEs) are increasingly being recognized as subclinical phenomena that might predict the development of various mental disorders that are not limited to the psychosis spectrum. Accumulating evidence suggests that attention-deficit/hyperactivity disorder (ADHD) and post-traumatic stress disorder (PTSD) are highly comorbid mental disorders. However, their interactive effect on the occurrence of PLEs has not been investigated so far. Therefore, in the present study we aimed to investigate the effect of interaction between ADHD and PTSD symptoms on the level of psychotic-like experiences (PLEs) in the non-clinical sample.

Methods

The study included 3,000 individuals aged 18-35 years with a negative history of psychiatric treatment. The symptoms of ADHD and PTSD were assessed using self-reports.

Results

There was a significant association of the interaction between ADHD and PTSD with the level of reporting PLEs. This association remained significant after adjustment for age, gender, the level of education, the current vocational situation, lifetime history of problematic substance use, and depressive symptoms. Post-hoc tests demonstrated significantly higher levels of reporting PLEs in participants with positive screening for both ADHD and PTSD compared to other subgroups of participants. Also, individuals with positive screening for one vulnerability (either ADHD or PTSD) reported significantly higher levels of reporting PLEs compared to those with a negative screening for ADHD and PTSD. In turn, no significant differences between individuals reporting one vulnerability, i.e., between those with positive screening for ADHD and those with positive screening for PTSD, were observed.

Conclusion

Findings from the present study imply that both PTSD and ADHD symptoms the interaction effect on the level of reporting PLEs that might be of importance for early intervention strategies. However, observed associations require replication in clinical samples.

Behavioral, Neurochemical and Developmental Effects of Chronic Oral Methylphenidate: A Review

The majority of animal studies on methylphenidate (MP) use intraperitoneal (IP) injections, subcutaneous (SC) injections, or the oral gavage route of administration. While all these methods allow for delivery of MP, it is the oral route that is clinically relevant. IP injections commonly deliver an immediate and maximum dose of MP due to their quick absorption. This quick-localized effect can give timely results but will only display a small window of the psychostimulant's effects on the animal model. On the opposite side of the spectrum, a SC injection does not accurately represent the pathophysiology of an oral exposure because the metabolic rate of the drug would be much slower. The oral-gavage method, while providing an oral route, possesses some adverse effects such as potential animal injury and can be stressful to the animal compared to voluntary drinking. It is thus important to allow the animal to have free consumption of MP, and drinking it to more accurately mirror human treatment. The use of a two-bottle drinking method allows for this. Rodents typically have a faster metabolism than humans, which means this needs to be considered when administering MP orally while reaching target pharmacokinetic levels in plasma. With this oral two-bottle approach, the pathophysiological effects of MP on development, behavior, neurochemistry and brain function can be studied. The present review summarizes these effects of oral MP which have important implications in medicine.

Breviscapine Ameliorates Fear Extinction and Anxiety in BALB/cJ Mice

OBJECTIVE

In this research, the influence of breviscapine on anxiety, fear elimination, and aggression and the potential mechanism was investigated.

METHODS

Anxiety and locomotion were analyzed by elevated plus maze and open field test in mice. Bussey-Saksida Mouse Touch Screen Chambers were used to perform fear conditioning. Territorial aggression was assessed by resident intruder test. Protein levels were evaluated by Western blot. Breviscapine improved fear-extinction learning in BALB/cJ mice.

RESULTS

Breviscapine at 20-100 mg/kg increased center cross number, total distance traveled, and velocity in a dose-dependent manner. On the other hand, breviscapine at 20-100 mg/kg decreased the immobility time in open field test. In addition, breviscapine at 20-100 mg/kg increased the ratio of time on the open arm, time on the distal parts of the open arm, and total distance traveled in elevated plus maze. Breviscapine at 100 mg/kg increased the average attack latency and decreased the number of attacks over the last 3 days of resident intruder test. In hippocampus, protein levels of postsynaptic density protein-95 and synaptophysin were elevated by breviscapine at these three doses.

CONCLUSION

The administration of breviscapine alleviates fear extinction, anxiety, and aggression, while increases locomotor in a dose-dependent manner, which might be associated with its influence on synaptic function.

The Relationship of Attention-Deficit/Hyperactivity Disorder With Posttraumatic Stress Disorder: A Two-Sample Mendelian Randomization and Population-Based Sibling Comparison Study

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) and posttraumatic stress disorder (PTSD) are associated, but it is unclear if this is a causal relationship or confounding. We used genetic analyses and sibling comparisons to clarify the direction of this relationship.

METHODS

Linkage disequilibrium score regression and 2-sample Mendelian randomization were used to test for genetic correlation (rg) and bidirectional causal effects using European ancestry genome-wide association studies of ADHD (20,183 cases and 35,191 controls) and 6 PTSD definitions (up to 320,369 individuals). Several additional variables were included in the analysis to verify the independence of the ADHD-PTSD relationship. In a population-based sibling comparison (N = 2,082,118 individuals), Cox regression models were fitted to account for time at risk, a range of sociodemographic factors, and unmeasured familial confounders (via sibling comparisons).

RESULTS

ADHD and PTSD had consistent rg (rg range, 0.43-0.52; p <  .001). ADHD genetic liability was causally linked with increased risk for PTSD (β = 0.367; 95% CI, 0.186-0.552; p = 7.68 × 10-5). This result was not affected by heterogeneity, horizontal pleiotropy (Mendelian randomization Egger intercept = 4.34 × 10-4, p = .961), or other phenotypes and was consistent across PTSD datasets. However, we found no consistent associations between PTSD genetic liability and ADHD risk. Individuals diagnosed with ADHD were at a higher risk for developing PTSD than their undiagnosed sibling (hazard ratio = 2.37; 95% CI, 1.98-3.53).

CONCLUSIONS

Our findings add novel evidence supporting the need for early and effective treatment of ADHD, as patients with this diagnosis are at significantly higher risk to develop PTSD later in life.

Emotional and sensory dysregulation as a possible missing link in attention deficit hyperactivity disorder: A review

Attention Deficit Hyperactivity Disorder (ADHD) is a common developmental disorder affecting 5-7% of adults and children. We surveyed the literature to examine ADHD through three pillars: developmental characteristics, symptomatology, and treatment strategies. Firstly, in terms of developmental characterstics, early life stress may increase the risk of developing ADHD symptoms according to animal models' research. Secondly, the current core symptoms of ADHD are comprised of inattention, hyperactivity, and impulsivity. However, the up-to-date literature indicates individuals with ADHD experience emotional and sensory dysregulation as well, which early-life stress may also increase the risk of. Finally, we discuss the therapeutic benefits of methylphenidate on both the current core ADHD symptoms and the sensory and emotional dysregulation found in those with ADHD. In summation, we surveyed the recent literature to analyze (i) the potential role of early-life stress in ADHD development, (ii) the involvement of emotional and sensory dysregulation in ADHD symptomatology and finally, (iii) the therapeutic intervention with methylphenidate, aiming to reduce the potential effect of early life stress in ADHD, and mainly emotional and sensory dysregulation. The apparent but currently less recognized additional symptoms of emotional and sensory dysregulation in ADHD call for further investigation of these possible causes and thus increasing treatments efficacy in individuals with ADHD.

Sex-specific metabolic signatures in methamphetamine addicts

Methamphetamine (METH) is a commonly abused addictive psychostimulant, and METH-induced neurotoxic and behavioural deficits are in a sex-specific manner. However, there is lack of biomarkers to evaluate METH addiction in clinical practice, especially for gender differences. We utilized ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to detect the serum metabolomics in METH addicts and controls, specially exploring the sex-specific metabolic alterations by METH abuse. We found that many differently expressed metabolites in METH addicts related to metabolisms of amino acid, energy, vitamin and neurological disorders. Further, METH abuse caused different patterns of metabolomics in a sex-specific manner. As to amino acid metabolism, L-phenylalanine, L-tryptophan and L-histidine in serum of male addicts and betaine in serum of female addicts were significantly changed by METH use. In addition, it seemed that purine and pyrimidine-related metabolites (e.g., xanthosine and adenosine 5'-monophosphate) in male and the metabolites of hormone (e.g., cortisol) and folate biosynthesis (e.g., 7,8-dihydrobiopterin and 4-hydroxybenzoic acid) in female were more sensitive to METH addiction. Our findings revealed that L-glutamic acid, L-aspartic acid, alpha-ketoglutarate acid and citric acid may be potential biomarkers for monitoring METH addiction in clinic. Considering sex-specific toxicity by METH, the metabolites of purine and pyrimidine metabolism in male and those of stress-related hormones in female may be used to facilitate the accurate diagnosis and treatment for METH addicts of different genders.

The effects of the recurrent social isolation stress on fear extinction and dopamine D2 receptors in the amygdala and the hippocampus

BACKGROUND

The present study assessed the influence of recurrent social isolation stress on the aversive memory extinction and dopamine D₂ receptors (D₂R) expression in the amygdala and the hippocampus subnuclei. We also analyzed the expression of epigenetic factors potentially associated with fear extinction: miRNA-128 and miRNA-142 in the amygdala.

METHODS

Male adult fear-conditioned rats had three episodes of 48 h social isolation stress before each fear extinction session in weeks intervals. Ninety minutes after the last extinction session, the D₂R expression in the nuclei of the amygdala and the hippocampus (immunocytochemical technique), and mRNA levels for D₂R in the amygdala were assessed (PCR). Moreover, we evaluated the levels of miRNA-128 and miRNA-142 in the amygdala.

RESULTS

It was found that recurrent social isolation stress decreased the fear extinction rate. The extinguished isolated rats were characterized by higher expression of D₂R in the CA1 area of the hippocampus compared to the extinguished and the control rats. In turn, the isolated group presented higher D₂R immunoreactivity in the CA1 area compared to the extinguished, the control, and the extinguished isolated animals. Moreover, the extinguished animals had higher expression of D₂R in the central amygdala than the control and the extinguished isolated rats. These changes were accompanied by the increase in miRNA-128 level in the amygdala in the extinguished isolated rats compared to the control, the extinguished, and the isolated rats. Moreover, the extinguished rats had lower expression of miRNA-128 compared to the control and the isolated animals.

CONCLUSIONS

Our results suggest that social isolation stress impairs aversive memory extinction and coexists with changes in the D₂R expression in the amygdala and hippocampus and increased expression of miRNA-128 in the amygdala.

Rosmarinus officinalis and Methylphenidate Exposure Improves Cognition and Depression and Regulates Anxiety-Like Behavior in AlCl3-Induced Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurological illness that causes severe cognitive impairment. AD patients also experience at least one of the neuropsychiatric symptoms including apathy, depression, and anxiety during the course of their life. Acetylcholine esterase inhibitors are the available treatment options to alleviate cognitive deficits, whereas methylphenidate (MPH), a psychostimulant, is considered for the treatment of apathy in AD patients. Rosmarinus officinalis, a perennial herb, has been potentially known to have antioxidant and anti-inflammatory properties. The present study investigated the potential effects of MPH and R. officinalis in comparison with the standard drug, Donepezil, on cognition, anxiety, and depression in the AlCl₃-induced mouse model of AD. The animals were divided into eight groups (n = 8, each). The results revealed that the MPH- and R. officinalis-treated groups significantly improved memory impairment, whereas R. officinalis substantially reduced depression and anxiety as compared with other treatment groups. MPH treatment induced an antidepressant effect and increased anxiety-like behavior. Moreover, the AlCl₃ exposure led to the formation of amyloid beta (Aβ) plaques in mice hippocampus; however, none of the tested drugs caused a significant reduction in amyloid burden at the selected doses. The present study suggested the potential of R. officinalis to improve memory as well as neuropsychiatric symptoms in AD. Although R. officinalis improved cognitive abilities, it did not reduce the amyloid plaque burden, which indicates that the memory-enhancing effects of R. officinalis are due to some alternate mechanism that needs to be explored further.

Modelling Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) Using Mice and Zebrafish

Autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD) are two debilitating neurodevelopmental disorders. The former is associated with social impairments whereas the latter is associated with inattentiveness, hyperactivity, and impulsivity. There is recent evidence that both disorders are somehow related and that genes may play a large role in these disorders. Despite mounting human and animal research, the neurological pathways underlying ASD and ADHD are still not well understood. Scientists investigate neurodevelopmental disorders by using animal models that have high similarities in genetics and behaviours with humans. Mice have been utilized in neuroscience research as an excellent animal model for a long time; however, the zebrafish has attracted much attention recently, with an increasingly large number of studies using this model. In this review, we first discuss ASD and ADHD aetiology from a general point of view to their characteristics and treatments. We also compare mice and zebrafish for their similarities and discuss their advantages and limitations in neuroscience. Finally, we summarize the most recent and existing research on zebrafish and mouse models of ASD and ADHD. We believe that this review will serve as a unique document providing interesting information to date about these models, thus facilitating research on ASD and ADHD.

Neuropsychological Characterization of Aggressive Behavior in Children and Adolescents with CD/ODD and Effects of Single Doses of Medications: The Protocol of the Matrics_WP6-1 Study

Aggressive behaviors and disruptive/conduct disorders are some of the commonest reasons for referral to youth mental health services; nevertheless, the efficacy of therapeutic interventions in real-world clinical practice remains unclear. In order to define more appropriate targets for innovative pharmacological therapies for disruptive/conduct disorders, the European Commission within the Seventh Framework Programme (FP7) funded the MATRICS project (Multidisciplinary Approaches to Translational Research in Conduct Syndromes) to identify neural, genetic, and molecular factors underpinning the pathogenesis of aggression/antisocial behavior in preclinical models and clinical samples. Within the program, a multicentre case-control study, followed by a single-blind, placebo-controlled, cross-over, randomized acute single-dose medication challenge, was conducted at two Italian sites. Aggressive children and adolescents with conduct disorder (CD) or oppositional defiant disorder (ODD) were compared to the same age (10–17 y) typically developing controls (TDC) on a neuropsychological tasks battery that included both “cold” (e.g., inhibitory control, decision making) and “hot” executive functions (e.g., moral judgment, emotion processing, risk assessment). Selected autonomic measures (heart rate variability, skin conductance, salivary cortisol) were recorded before/during/after neuropsychological testing sessions. The acute response to different drugs (methylphenidate/atomoxetine, risperidone/aripiprazole, or placebo) was also examined in the ODD/CD cohort in order to identify potential neuropsychological/physiological mechanisms underlying aggression. The paper describes the protocol of the clinical MATRICS WP6-1 study, its rationale, the specific outcome measures, and their implications for a precision medicine approach.

Extinction trial spacing across days differentially impacts fear regulation in adult and adolescent male mice

Fear regulation changes as a function of age and adolescence is a key developmental period for the continued maturation of fear neural circuitry. A consistent finding in the literature is diminished extinction retention in adolescents. However, these studies often directly compare adolescents to adults using a single protocol and therefore provide little insight into learning parameters that improve adolescent fear regulation. Studies in adults highlight the benefits of spaced learning over massed learning. These findings have been extended to fear regulation, with adult rodents exhibiting improved extinction learning and retention when cues are distributed over days versus a single session. However, similar studies have not been performed in adolescents. Here, we systematically examine the impact of trial spacing across days on fear regulation. Adolescent or adult male mice were exposed to one of three extinction paradigms that presented the same number of trials but differed in the temporal distribution of trials across days (one day, two days, or four days). We found that introducing consolidation events into the protocol improves adult extinction learning and short-term extinction retention but these effects disappear after two weeks. For adolescents, all three protocols were comparably effective in reducing freezing across extinction training and improved retention at both short-term and long-term fear recall time points relative to extinction-naive mice. These findings suggest that extinction protocols that incorporate consolidation events are optimal for adults but additional booster training may be required for enduring efficacy. In contrast, protocols incorporating either massed or spaced presentations show immediate and enduring benefits for adolescents.

Haloperidol and methylphenidate alter motor behavior and responses to conditioned fear of Carioca Low-conditioned Freezing rats

Animal models are important tools for studying neuropsychological disorders. Considering their limitations, a more extensive translational research must encompass data that are generated from several models. Therefore, a comprehensive characterization of these models is needed in terms of behavior and neurophysiology. The present study evaluated the behavioral responses of Carioca Low-conditioned Freezing (CLF) rats to haloperidol and methylphenidate. The CLF breeding line is characterized by low freezing defensive responses to contextual cues that are associated with aversive stimuli. CLF rats exhibited a delayed response to haloperidol at lower doses, needing higher doses to reach similar levels of catatonia as control randomly bred animals. Methylphenidate increased freezing responses to conditioned fear and induced motor effects in the open field. Thus, CLF rats differ from controls in their responses to both haloperidol and methylphenidate. Because of the dopamine-related molecular targets of these drugs, we hypothesize that dopaminergic alterations related to those of animal models of hyperactivity and attention disorders might underlie the observed phenotypes of the CLF line of rats.

CDH2 mutation affecting N-cadherin function causes attention-deficit hyperactivity disorder in humans and mice

Attention-deficit hyperactivity disorder (ADHD) is a common childhood-onset psychiatric disorder characterized by inattention, impulsivity and hyperactivity. ADHD exhibits substantial heritability, with rare monogenic variants contributing to its pathogenesis. Here we demonstrate familial ADHD caused by a missense mutation in CDH2, which encodes the adhesion protein N-cadherin, known to play a significant role in synaptogenesis; the mutation affects maturation of the protein. In line with the human phenotype, CRISPR/Cas9-mutated knock-in mice harboring the human mutation in the mouse ortholog recapitulated core behavioral features of hyperactivity. Symptoms were modified by methylphenidate, the most commonly prescribed therapeutic for ADHD. The mutated mice exhibited impaired presynaptic vesicle clustering, attenuated evoked transmitter release and decreased spontaneous release. Specific downstream molecular pathways were affected in both the ventral midbrain and prefrontal cortex, with reduced tyrosine hydroxylase expression and dopamine levels. We thus delineate roles for CDH2-related pathways in the pathophysiology of ADHD.

Molecular mechanisms of attention-deficit hyperactivity disorder (ADHD) are not fully understood. Here the authors demonstrate a mutation in CDH2, encoding N-cadherin, that is associated with ADHD, and in a mouse model, delineate molecular electrophysiological characteristics associated with this mutation.

Experimentally altered male mating behaviour affects offspring exploratory behaviour via nongenetic paternal effects

Evidence is emerging that fathers can have nongenetic effects on the phenotypes of their offspring. Most studies have focused on the role that nongenetic modifications to sperm can have on offspring phenotype; however, fathers can also have nongenetic effects on offspring through their interactions with females, called female-mediated paternal effects. These effects can occur in situations where male phenotype, e.g. behaviour or morphology, affects female stress and/or provisioning of offspring. These effects are potentially widespread, but few studies have explicitly investigated the role of female-mediated paternal effects on offspring phenotype. Here, we asked if male mating interactions can affect offspring via female mediated paternal effects in the Trinidadian guppy, Poecilia reticulata. To do this, we manipulated mating behaviour by: (i) administering a drug known to affect the neurotransmitter dopamine, and (ii) varying the familiarity of potential mates, which affects attractiveness in this species. With these treatments, we successfully manipulated the mating behaviour of male guppies and female preference for those males. Further, we found significant effects of sire mating behaviour, sire drug treatment, and parental familiarity status on behavioural measures of offspring anxiety in response to a novel object. Because Control offspring of 'familiar' and 'unfamiliar' pairs differed in their behaviour, our results cannot be solely attributed to potential nongenetic modifications to sperm caused by the drug. These results emphasize the importance of female-mediated paternal effects, including those caused by altered male mating behaviour, in shaping offspring phenotype.