Abnormal fear conditioning and amygdala processing in an animal model of autism.

A core feature of autism spectrum disorders is the impairment in social interactions. Among other brain regions, a deficit in amygdala processing has been suggested to underlie this impairment, but whether the amygdala is processing fear abnormally in autism, is yet not clear. We used the valproic acid (VPA) rat model of autism to (a) screen for autism-like symptoms in rats, (b) test for alterations in amygdala-dependent fear processing, and (c) evaluate neuronal reactivity and synaptic plasticity in the lateral amygdala by means of in vitro single-cell electrophysiological recordings. VPA-treated animals displayed several symptoms common to autism, among them impaired social interactions and increased repetitive behaviors. Furthermore, VPA-treated rats were more anxious and exhibited abnormally high and longer lasting fear memories, which were overgeneralized and harder to extinguish. On the cellular level, the amygdala was hyperreactive to electrical stimulation and displayed boosted synaptic plasticity as well as a deficit in inhibition. We show for the first time enhanced, overgeneralized and resistant conditioned fear memories in an animal model of autism. Such hyperfear could be caused by the hyperreactivity and hyperplasticity found in the lateral amygdala, which may in turn be due to a deficit in the inhibitory system of the amygdala. We hypothesize an 'aversive world' syndrome that could, even if not a primary cause of the disorder itself, underlie some core symptoms in autism, such as impairments in social interactions and resistance to rehabilitation.     

From anxiety to autism: spectrum of abnormal social behaviors modeled by progressive disruption of inhibitory neuronal function in the basolateral amygdala in Wistar rats

Rationale Social behaviors are disrupted in several psychiatric disorders. The amygdala is a key brain region involved in social behaviors, and amygdala pathology has been implicated in disease states ranging from social anxiety disorder to autism. Objective To test the effects of progressive disruption of the inhibitory function within the basolateral nucleus of the amygdala (BLA) on conspecific social interaction in rats and investigate functional networks from the ventral medial prefrontal cortex (mPFCv) to the BLA. Materials and methods BLA inhibitory tone was disrupted by priming it with the stress-peptide corticotrophin releasing factor (CRF) receptor agonist urocortin 1 (Ucn 1, 6 fmol), or by selective lesioning of a subset of BLA-GABAergic interneurons containing neurokinin 1 receptors using the targeted toxin SSP-Saporin. The effects of the disruption of GABAergic tone in the BLA were examined using a repeated exposure and habituation paradigm of social interaction (SI/h). Lesions and selectivity of lesions were confirmed postmortem. Additionally, effects of stimulating mPFCv on cFos activity in interneurons of the BLA were examined. Results Rats primed with Ucn 1 showed persistent social inhibition, which could be overcome with habituation, putatively modeling social anxiety. Rats with a selective lesioning of a subset of GABAergic interneurons in the BLA exhibited persistent social inhibition that was not reversed by SI/h paradigm. We also demonstrate selective functional inputs to this subset of interneurons when mPFCv was activated. Conclusions These models with different gradations of disrupted BLA inhibition could help to study social dysfunction in disorders ranging from social anxiety to autism spectrum disorders. This work was partially supported by PHS grants RO1 MH65702 and R01 MH52619 to AS.     

Drug therapy in autism: a present and future perspective

Autism is a neurodevelopmental disorder, with a multifactorial etiology, characterized by severe abnormalities in communications, social awareness and skills, and the presence of restrictive and stereotyped patterns of behaviors. It is traditionally considered a “static” encephalopathic disorder without any specific cure and few effective biomedical interventions. There are various factors which are involved in the etiopathogenesis of autism or autism spectrum disorder (ASD) such as impaired immune responses, neuroinflammation, abnormal neurotransmission, oxidative stress, mitochondrial dysfunction, environmental toxins and stressors. The autism is often associated with a number of genetic disorders such as fragileXsyndrome, tuberous sclerosis, epilepsy and Down syndrome. The recent approaches to autism treatment included various non-pharmacological and pharmacological therapy such as food supplementation, detoxification, treatment of neuroinflammation, immunologic treatments and psychotropic medications, which are found to be effective in treating various behavioral symptoms of autism. In current practice, there is no curative treatment for autism but the recommended treatment for autism involves educational therapies: speech therapy, sensory integration therapy, auditory therapy. There are classes of different pharmacological agents which are found to be effective in improving behavioral symptoms of ASD such as neurotransmitter reuptake inhibitors (fluoxetine), tricyclic antidepressants (imipramine), anticonvulsants (lamotrigine), atypical antipsychotics (clozapine), acetylcholinesterase inhibitors (rivastigmine), etc. New classes of drugs with novel mechanisms of action should be there so that this disorder will become less prevalent in the future.     

Oxytocin infusion reduces repetitive behaviors in adults with autistic and Asperger's disorders.

Autism is a neurodevelopmental disorder characterized by dysfunction in three core behavioral domains: repetitive behaviors, social deficits, and language abnormalities. There is evidence that abnormalities exist in peptide systems, particularly the oxytocin system, in autism spectrum patients. Furthermore, oxytocin and the closely related peptide vasopressin are known to play a role in social and repetitive behaviors. This study examined the impact of oxytocin on repetitive behaviors in 15 adults with autism or Asperger's disorder via randomized double-blind oxytocin and placebo challenges. The primary outcome measure was an instrument rating six repetitive behaviors: need to know, repeating, ordering, need to tell/ask, self-injury, and touching. Patients with autism spectrum disorders showed a significant reduction in repetitive behaviors following oxytocin infusion in comparison to placebo infusion. Repetitive behavior in autism spectrum disorders may be related to abnormalities in the oxytocin system, and may be partially ameliorated by synthetic oxytocin infusion.     

What is Known About Autism

Autism is a neurodevelopmental disorder of genetic origins, with a heritability of about 90%. Autistic disorder is classed within the broad domain of pervasive developmental disorders (PDD) that also includes Rett syndrome, childhood disintegrative disorder, Asperger syndrome, and PDD not otherwise specified (PDD-NOS). Prevalence estimates suggest a rate of 0.1-0.2% for autism and 0.6% for the range of PDD disorders. There is considerable phenotypic heterogeneity within this class of disorders as well as continued debate regarding their clinical boundaries. Autism is the prototypical PDD, and is characterized by impairments in three core domains: social interaction, language development, and patterns of behavior (restricted and stereotyped). Clinical pattern and severity of impairment vary along these dimensions, and the level of cognitive functioning of individuals with autism spans the entire range, from profound mental retardation to superior intellect. There is no single biological or clinical marker for autism, nor is it expected that a single gene is responsible for its expression; as many as 15+ genes may be involved. However, environmental influences are also important, as concordance in monozygotic twins is less than 100% and the phenotypic expression of the disorder varies widely, even within monozygotic twins. Multiple susceptibility factors are being explored using varied methodologies, including genome-wide linkage studies, and family- and case-control candidate gene association studies. This paper reviews what is currently known about the genetic and environmental risk factors, neuropathology, and psychopharmacology of autism. Discussion of genetic factors focuses on the findings from linkage and association studies, the results of which have implicated the involvement of nearly every chromosome in the human genome. However, the most consistently replicated linkage findings have been on chromosome 7q, 2q, and 15q. The positive associations from candidate gene studies are largely unreplicated, with the possible exceptions of the GABRB3 and serotonin transporter genes. No single region of the brain or pathophysiological mechanism has yet been identified as being associated with autism. Postmortem findings, animal models, and neuroimaging studies have focused on the cerebellum, frontal cortex, hippocampus, and especially the amygdala. The cerebello-thalamo-cortical circuit may also be influential in autism. There is evidence that overall brain size is increased in some individuals with autism. Presently there are no drugs that produce major improvements in the core social or pragmatic language deficits in autism, although several have limited effects on associated behavioral features. The application of new techniques in autism research is being proposed, including the investigation of abnormal regulation of gene expression, proteomics, and the use of MRI and postmortem analysis of the brain.     

Transdiagnostic deviant facial recognition for implicit negative emotion in autism and schizophrenia

Impaired facial affect recognition (FAR) is observed in schizophrenia and autism spectrum disorder (ASD) and has been linked to amygdala and fusiform gyrus dysfunction. ASD patient's impairments seem to be more pronounced during implicit rather than explicit FAR, whereas for schizophrenia data are inconsistent. However, there are no studies comparing both patient groups in an identical design. The aim of this three-group study was to identify (i) whether FAR alterations are equally present in both groups, (ii) whether they are present rather during implicit or explicit FAR, (iii) and whether they are conveyed by similar or disorder-specific neural mechanisms. Using fMRI, we investigated neural activation during explicit and implicit negative and neutral FAR in 33 young-adult individuals with ASD, 20 subjects with paranoid-schizophrenia and 25 IQ- and gender-matched controls individuals. Differences in activation patterns between each clinical group and controls, respectively were found exclusively for implicit FAR in amygdala and fusiform gyrus. In addition, the ASD group additionally showed reduced activations in medial prefrontal cortex (PFC), bilateral dorso-lateral PFC, ventro-lateral PFC, posterior-superior temporal sulcus and left temporo-parietal junction. Although subjects with ASD showed more widespread altered activation patterns, a direct comparison between both patient groups did not show disorder-specific deficits in neither patient group. In summary, our findings are consistent with a common neural deficit during implicit negative facial affect recognition in schizophrenia and autism spectrum disorders.     

Increased repetitive behaviours and prolactin responsivity to oral m-chlorophenylpiperazine in adults with autism spectrum disorders

Autism is a neurodevelopmental disorder characterized by dysfunction in three primary behavioural domains: repetitive behaviours, social deficits, and language abnormalities. There is evidence that abnormalities exist in the serotonin (5-HT) system in autism spectrum patients. Furthermore, 5-HT is known to play a role in repetitive and social behaviours. This study examined the effect of m-chlorophenylpiperazine (m-CPP) on repetitive behaviours and prolactin response in 11 adults with autism or Aspergers disorder and 8 age- and gender-matched healthy controls via randomized double-blind, m-CPP and placebo challenges. The primary outcome measure was an instrument rating six repetitive behaviours: need to know, repeating, ordering, need to tell/ask, self-injury, and touching. Patients with autism spectrum disorders showed a significant increase in repetitive behaviours at end-point following oral m-CPP in comparison to placebo. Additionally subjects with autism spectrum disorders showed a significantly increased prolactin response to m-CPP compared to normal controls, with neither group responding to placebo. This study provides further evidence for altered 5-HT sensitivity in individuals with autism spectrum disorders, as well as a possible relationship between repetitive behaviours in autism spectrum disorders and abnormalities in the 5-HT system.     

Early amygdala damage in the rat as a model for neurodevelopmental psychopathological disorders.

Neurodevelopmental disorders in medial temporal lobe structures may underlie psychopathological diseases such as schizophrenia and autism. To construct an animal model for these developmental disorders, social and non-social behavioural responses were assessed in rats with ibotenic acid lesions of the (baso-)lateral and central amygdala or ventral hippocampus, induced early in life. Lesioning the amygdala on day 7 after birth resulted in a variety of behavioural disturbances later in life, whereas after similar lesions on day 21 after birth no disturbances developed, except for deficits in social behaviours. Lesioning the hippocampus led to much less disturbances. The results show that amygdala and hippocampus damage at a specific point early in life results in enduring behavioural disturbances that become more manifest after puberty. In particular, lesions of the amygdala on day 7 of life may serve as a rat model with face and construct validity for neurodevelopmental disorders in studying psychopathology.     

Recent trends in pharmacotherapy for anxiety disorders]

Since the introduction of SSRIs, pharmacotherapy for anxiety disorders has significantly changed. Although the SSRIs are considered to be a first-line treatment for the most of anxiety disorders benzodiazepines are still widely used in clinical practice despite the risk of dependence and strong recommendation for their use as a second-line. The SSRIs only replaced tricyclic antidepressants and the MAO inhibitors especially in the treatment of panic disorder, obsessive-compulsive disorder and social phobia. Combination of the SSRIs and the benzodiazepines is widely used. Recently it has been suggested that the combination of SSRI and benzodiazepine is rational, because each drug has a different mechanism of action, the benzodiazepines enhancing GABAergic transmission, and the SSRIs stimulating the 5-HT1A receptor that may inhibit the postsynaptic neuronal excitability in the amygdala and the prefrontal cortex that comprise the brain circuit of fear and anxiety. Recent imaging studies suggested the hyperactivity of the amygdala in the patients with generalized social anxiety disorder and successful treatment with cognitive behavioral therapy or SSRI might significantly reduce the hyperactivity of the amygdala. It was suggested that the rational combination of SSRIs and benzodiazepines seems to be an effective and practical way of treatment for most anxiety disorders.     

Early Social Enrichment Rescues Adult Behavioral and Brain Abnormalities in a Mouse Model of Fragile X Syndrome

Converging lines of evidence support the use of environmental stimulation to ameliorate the symptoms of a variety of neurodevelopmental disorders. Applying these interventions at very early ages is critical to achieve a marked reduction of the pathological phenotypes. Here we evaluated the impact of early social enrichment in Fmr1-KO mice, a genetic mouse model of fragile X syndrome (FXS), a major developmental disorder and the most frequent monogenic cause of autism. Enrichment was achieved by providing male KO pups and their WT littermates with enhanced social stimulation, housing them from birth until weaning with the mother and an additional nonlactating female. At adulthood they were tested for locomotor, social, and cognitive abilities; furthermore, dendritic alterations were assessed in the hippocampus and amygdala, two brain regions known to be involved in the control of the examined behaviors and affected by spine pathology in Fmr1-KOs. Enrichment rescued the behavioral FXS-like deficits displayed in adulthood by Fmr1-KO mice, that is, hyperactivity, reduced social interactions, and cognitive deficits. Early social enrichment also eliminated the abnormalities shown by adult KO mice in the morphology of hippocampal and amygdala dendritic spines, namely an enhanced density of immature vs mature types. Importantly, enrichment did not induce neurobehavioral changes in WT mice, thus supporting specific effects on FXS-like pathology. These findings show that early environmental stimulation has profound and long-term beneficial effects on the pathological FXS phenotype, thereby encouraging the use of nonpharmacological interventions for the treatment of this and perhaps other neurodevelopmental diseases.     

Risperidone: a potential treatment for autism

Autistic disorder (autism) is a neuropsychiatric syndrome characterized by marked deficits in reciprocal social relatedness, communication impairment and a narrow range of interests and/or repetitive behaviors. Autism is frequently associated with, but distinct from, mental retardation. It is classified as a subtype of pervasive developmental disorder (PDD) along with 'PDD not otherwise specified' (NOS) and Asperger's disorder. These disorders have in common marked impairments in social relatedness. Individuals with autism may also have other symptoms that become the primary focus of psychiatric treatment. These associated symptoms include aggression, self-injury, irritability and anxiety.     

Biological basis of anxiety disorders and serotonergic anxiolytics]

Selective serotonin reuptake inhibitors (SSRIs) have wide indications for the treatment of anxiety disorders, including panic disorder, generalized anxiety disorder, posttraumatic stress disorder, obsessive-compulsive disorder and social anxiety disorder in addition to depression. Until recently, no animal model has been available for screening the anxiolytic effect of SSRIs and studying its mechanism of action. We have investigated the relationship between serotonin neurotransmission and anxiety using conditioned fear stress (CFS), an animal model of anxiety. CFS increased serotonin neurotransmission in the medial prefrontal cortex and amygdala. In behavioral pharmacological studies, SSRIs, serotonin1A agonists and monoamine oxidase inhibitors, which are assumed to facilitate serotonin neurotransmission, decreased conditioned freezing, an index of anxiety or fear, in CFS. In vivo microdialysis studies showed that serotonin neurotransmission in the medial prefrontal cortex increased after recovery from the freezing behavior. Microinjection of SSRI to the basolateral nucleus of the amygdala reduced conditioned freezing, indicating that the amygdala is one of target brain sites of anxiolytic action of SSRIs. Furthermore, CFS-induced c-Fos expression in the basolateral nucleus of the amygdala was reduced by SSRI pretreatment. Taken together, recent studies indicate that facilitation of brain serotonin neurotransmission decreases anxiety in agreement with the clinical evidence.     

Prenatal Stress Alters the Development of Socioemotional Behavior and Amygdala Neuron Excitability in Rats

Prenatal stress (PS) is a risk factor for neurodevelopmental disorders with diverse ages of onset and socioemotional symptoms. Some PS-linked disorders involve characteristic social deficits, such as autism spectrum disorders and schizophrenia, but PS also promotes anxiety disorders. We propose the diversity of symptoms following PS arises from perturbations to early brain development. To this end, we characterized the effects of PS on the developmental trajectory of physiology of the amygdala, a late-developing center for socioemotional control. We found that PS dampened socioemotional behavior and reduced amygdala neuron excitability in offspring during infancy (at postnatal days (P)10, 14, 17 and 21), preadolescence (day 28), and adulthood (day 60). PS offspring in infancy produced fewer isolation-induced vocalizations and in adulthood exhibited less anxiety-like behavior and deficits in social interaction. PS neurons had a more hyperpolarized resting membrane potential from infancy to adulthood and produced fewer action potentials. Moreover, adult amygdala neurons from PS animals expressed larger action potential afterhyperpolarizations and H-current relative to controls, further limiting excitability. Our results suggest that PS can suppress socioemotional behavior throughout development and produce age-specific alterations to amygdala physiology.     

Genetics and epigenetics in autism]

Autism is a behaviorally defined syndrome characterized by impaired social interaction and communication, and restricted, stereotyped interests and behaviors. Several lines of evidence support the contention that genetic factors are a large component to autism etiology. However, in spite of vigorous genetic studies, no single causative or susceptibility gene common in autism has been identified. Thus multiple susceptibility genes in interaction are considered to account for the disorder. Furthermore, environmental risk factors can accelerate the autism development of. Recent advances in understanding the epigenetic regulation may shed light on the interaction among multiple genetic factors and environmental factors.     

Aripiprazole for treating irritability associated with autism spectrum disorders

ABSTRACT

Introduction: Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a reported prevalence of 1 in 59 people. Its core features are persistent deficits in social communication and restricted, repetitive patterns of behavior or interests. Individuals with ASD have a high incidence of secondary problems with mood lability, tantrums, self-injurious behavior and aggressiveness toward others. Collectively, these behaviors are often referred to as irritability. Many medications have been used to treat irritability in autism, with aripiprazole one of only two medications approved in the USA for this purpose.

Areas covered: Herein, the authors review the evidence supporting the use of aripiprazole for treating irritability in autism, including the pivotal trials leading to regulatory approval and long-term studies conducted post-approval. They utilized PubMed, searching all English language publications since 2000, using the terms aripiprazole, autism, autism spectrum disorder, pervasive developmental disorder, Asperger’s disorder, and irritability, and focused on clinical trials and review articles.

Expert opinion: Multiple studies have shown the clear benefit of aripiprazole in the treatment of irritability in autism disorders compared to placebo. Often underemphasized are the metabolic effects, the proper monitoring for these effects, and the need for periodic reassessment to determine if ongoing treatment is needed.     

Fluoxetine but not risperidone increases sociability in the BTBR mouse model of autism

Autism, a neurodevelopmental disorder, is characterized by abnormal social interactions, impaired social communication and repetitive behaviors and/or restricted interests, along with several associated symptoms including irritability and anxiety. Risperidone is approved for the irritability and self-injurious behaviors found in autism. Fluoxetine is under evaluation for the repetitive behaviors and anxiety associated with autism. These two drugs were evaluated in the BTBR T + tf/J (BTBR) mouse model of autism and C57BL/6J (B6) mice by using the three-chambered social approach test and elevated plus maze to determine effects on sociability and anxiety. Fluoxetine increased sociability, defined as time spent with a stranger mouse, in the BTBR mice without affecting anxiety-like behavior in the elevated plus maze. Fluoxetine did not significantly change either behavior in the B6 mice. Risperidone did not affect sociability or anxiety-like behaviors and had a sedative-like effect at higher doses. These findings suggest that fluoxetine may have some therapeutic efficacy for treating the social behaviors in autism.     

Mirror system based therapy for autism spectrum disorders

This paper reviews the present theories and empirical research of autisms’ cognitive research and mirror systems and introduces a new hypothesis about the causes of autism spectrum disorders (ASD): autistic mirror neuron dysfunction hypothesis. ASD subjects show obvious lack of the activation of the mirror system during the task of observation or emotional cognition. It is significant to investigate the mirror system for revealing the causes of autism and it is also helpful for developing new ways to diagnose or treat this disorder.     

孤独症研究进展

儿童孤独症是一种严重的多功能发育障碍,目前尚无人能证明孤独症的确切病因,更无确切的临床治疗。近期的研究倾向于是生物基因因素所导致的脑功能普遍发育障碍。孤独症的心理理论与其言语、交往能力、社会功能以及想象力有密切的关系。本文回顾了儿童孤独症的发展历史和近期预后状况,最后着重从临床和应用角度,探讨心理理论有关的孤独症早期检测和训练问题,并提出目前研究存在的问题和未来研究方向。帮助提高医务人员和家长对儿童孤独症的认识水平及帮助父母正确对待孤独症患儿,可预防孤独症的发生和改善其预后。     

基于突触功能异常的自闭症发病机制研究进展

作为神经元间行使功能和信息传递的关键部位,突触的功能异常在自闭症病理过程中扮演的角色备受关注。在自闭症动物模型或患者中,突触形态学发生了变化,主要表现为树突棘密度、树突棘形态比例及突触后致密物质的异常,这些可能与突触的发生、修剪及成熟过程受到干扰相关。此外,相关突触蛋白如NLGNs、NRXNs和SHANK3等在自闭症患者中均发生了突变。实验研究也发现多条信号通路通过改变突触功能从而影响了自闭症疾病模型的社会交往能力。截止目前为止,自闭症的病理机制和药物靶标仍未可知。本文就基于突触功能异常的自闭症发病机制研究进行综述。     

Oxytocin Attenuates Amygdala Reactivity to Fear in Generalized Social Anxiety Disorder

Patients with generalized social anxiety disorder (GSAD) exhibit heightened activation of the amygdala in response to social cues conveying threat (eg, fearful/angry faces). The neuropeptide oxytocin (OXT) decreases anxiety and stress, facilitates social encounters, and attenuates amygdala reactivity to threatening faces in healthy subjects. The goal of this study was to examine the effects of OXT on fear-related amygdala reactivity in GSAD and matched healthy control (CON) subjects. In a functional magnetic resonance imaging study utilizing a double-blind placebo-controlled within-subjects design, we measured amygdala activation to an emotional face matching task of fearful, angry, and happy faces following acute intranasal administration of OXT (24 IU or 40.32 μg) and placebo in 18 GSAD and 18 CON subjects. Both the CON and GSAD groups activated bilateral amygdala to all emotional faces during placebo, with the GSAD group exhibiting hyperactivity specifically to fearful faces in bilateral amygdala compared with the CON group. OXT had no effect on amygdala activity to emotional faces in the CON group, but attenuated the heightened amygdala reactivity to fearful faces in the GSAD group, such that the hyperactivity observed during the placebo session was no longer evident following OXT (ie, normalization). These findings suggest that OXT has a specific effect on fear-related amygdala activity, particularly when the amygdala is hyperactive, such as in GSAD, thereby providing a brain-based mechanism of the impact of OXT in modulating the exaggerated processing of social signals of threat in patients with pathological anxiety.