The serotonergic system: its role in pathogenesis and early developmental treatment of autism

The 'PSILAUT' protocol: an experimental medicine study of autistic differences in the function of brain serotonin targets of psilocybin

BACKGROUND

The underlying neurobiology of the complex autism phenotype remains obscure, although accumulating evidence implicates the serotonin system and especially the 5HT2A receptor. However, previous research has largely relied upon association or correlation studies to link differences in serotonin targets to autism. To directly establish that serotonergic signalling is involved in a candidate brain function our approach is to change it and observe a shift in that function. We will use psilocybin as a pharmacological probe of the serotonin system in vivo. We will directly test the hypothesis that serotonergic targets of psilocybin - principally, but not exclusively, 5HT2A receptor pathways-function differently in autistic and non-autistic adults.

METHODS

The 'PSILAUT' "shiftability" study is a case-control study autistic and non-autistic adults. How neural responses 'shift' in response to low doses (2 mg and 5 mg) of psilocybin compared to placebo will be examined using multimodal techniques including functional MRI and EEG. Each participant will attend on up to three separate visits with drug or placebo administration in a double-blind and randomized order.

RESULTS

This study will provide the first direct evidence that the serotonin targets of psilocybin function differently in the autistic and non-autistic brain. We will also examine individual differences in serotonin system function.

CONCLUSIONS

This work will inform our understanding of the neurobiology of autism as well as decisions about future clinical trials of psilocybin and/or related compounds including stratification approaches.

TRIAL REGISTRATION

NCT05651126.

Branched-chain amino acids as adjunctive-alternative treatment in patients with autism: a pilot study

The branched-chain amino acid (BCAA) is a group of essential amino acids that are involved in maintaining the energy balance of a human being as well as the homoeostasis of GABAergic, glutamatergic, serotonergic and dopaminergic systems. Disruption of these systems has been associated with the pathophysiology of autism while low levels of these amino acids have been discovered in patients with autism. A pilot open-label, prospective, follow-up study of the use of BCAA in children with autistic behaviour was carried out. Fifty-five children between the ages of 6 and 18 participated in the study from May 2015 to May 2018. We used a carbohydrate-free BCAA-powdered mixture containing 45·5 g of leucine, 30 g of isoleucine and 24·5 g of valine in a daily dose of 0·4 g/kg of body weight which was administered every morning. Following the initiation of BCAA administration, children were submitted to a monthly psychological examination. Beyond the 4-week mark, BCAA were given to thirty-two people (58·18 %). Six of them (10·9 %) discontinued after 4-10 weeks owing to lack of improvement. The remaining twenty-six children (47·27 %) who took BCAA for longer than 10 weeks displayed improved social behaviour and interactions, as well as improvements in their speech, cooperation, stereotypy and, principally, their hyperactivity. There were no adverse reactions reported during the course of the treatment. Although these data are preliminary, there is some evidence that BCAA could be used as adjunctive treatment to conventional therapeutic methods for the management of autism.

Increasing maternal age predicts placental protein expression critical for fetal serotonin metabolism: Potential implications for neurodevelopmental research

High fetal exposure to serotonin and increasing maternal age both contribute to the risk for neurodevelopmental disorders. While identifying covariates for a study of placental protein expression, we found a significant negative correlation between maternal age and the expression of monoamine oxidase A (MAOA), and a significant positive correlation between maternal age and the expression of the serotonin transporter SERT. MAOA and SERT play key roles in placental serotonin metabolism relevant to fetal neurodevelopment. These preliminary findings suggest that the effect of increasing maternal age on neurodevelopmental risk may be mediated in part by changes in placental protein expression relevant to fetal serotonin metabolism.

Maternal Serotonergic Antidepressant Use in Pregnancy and Risk of Seizures in Children

BACKGROUND AND OBJECTIVES

To evaluate whether children born to women who use serotonergic antidepressants during pregnancy have higher risk of neonatal seizures and epilepsy.

METHODS

We used Swedish register-based data to examine associations between maternal reported use of selective serotonin reuptake inhibitors (SSRIs) or serotonin-norepinephrine reuptake inhibitors (SNRIs) in pregnancy and diagnosis of neonatal seizures or epilepsy in >1.2 million children. To account for systematic differences between exposed and unexposed children, we adjusted for a wide range of measured confounders. After first evaluating the role of maternal indication for SSRI/SNRI use (i.e., depression or anxiety) and parental epilepsy, we adjusted for remaining parental background factors (e.g., age, comorbidities, education, and family socioeconomic indices) and pregnancy-specific characteristics (e.g., maternal use of other psychotropic medications and tobacco smoking in early pregnancy).

RESULTS

Compared with all other children, children of women who reported use of SSRI/SNRI in pregnancy had an elevated risk of neonatal seizures and epilepsy (risk ratio [RR] 1.41, 95% CI 1.03-1.94; hazard ratio [HR] 1.21, 95% CI 1.03-1.43, respectively). The estimates of association were attenuated by adjustment for maternal indications for SSRI/SNRI use (RR 1.30, 95% CI 0.94-1.80; HR 1.13, 95% CI 0.95-1.33), but not by additional adjustment for parental history of epilepsy. Full adjustment for all measured parental and pregnancy-specific factors resulted in substantial attenuation of the remaining associations (RR 1.10, 95% CI 0.79-1.53; HR 0.96, 95% CI 0.81-1.14).

DISCUSSION

We found no support for the concern that maternal SSRI/SNRI use in pregnancy increases children's risk for neonatal seizures or epilepsy.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that exposure to SSRIs/SNRIs in the first trimester of pregnancy is not associated with an increased incidence of neonatal seizures/epilepsy.

Brain Derived Neurotrophic Factor and Serotonin Levels in Autistic Children: Do They Differ in Obesity?

BACKGROUND: The risk of obesity among autism spectrum disorder (ASD) children is high which could be related to a disorder in their metabolism. Brain derived neurotrophic factor (BDNF) is involved in metabolic control, language behavior, and intellectual development. Serotonin has a role in satiety and energy expenditure. AIM: Therefore, the aim of this study was to measure the serum levels of BDNF and serotonin in obese compared to non-obese ASD children. The influence of obesity on ASD severity, intellectual, and language development was also investigated. METHODS: The study included 60 autistic children (Group I: 30 ASD children with obesity and Group II: 30 ASD children without obesity). The serum BDNF and serotonin levels were estimated by ELISA and by high-performance liquid chromatography. RESULTS: All participants manifested delayed language development. Almost all of them had intellectual disability. The difference between groups regarding ASD severity, language, and intellectual development was non-significant. However, BDNF level in obese group was less than that in the other group while serotonin was higher in the obese group with significant statistical difference. CONCLUSION: The difference between the groups regarding the levels of BDNF and serotonin, which are involved in the brain development, could be related to obesity. The influence of obesity on ASD severity, intellectual, and language development of ASD children was not distinctive in the participants. The influence of such markers on ASD severity and cognitive performance needs further investigations.

Systemic enhancement of serotonin signaling reverses social deficits in multiple mouse models for ASD

Autism spectrum disorder (ASD) is a common set of heterogeneous neurodevelopmental disorders resulting from a variety of genetic and environmental risk factors. A core feature of ASD is impairment in prosocial interactions. Current treatment options for individuals diagnosed with ASD are limited, with no current FDA-approved medications that effectively treat its core symptoms. We recently demonstrated that enhanced serotonin (5-HT) activity in the nucleus accumbens (NAc), via optogenetic activation of 5-HTergic inputs or direct infusion of a specific 5-HT1b receptor agonist, reverses social deficits in a genetic mouse model for ASD based on 16p11.2 copy number variation. Furthermore, the recreational drug MDMA, which is currently being evaluated in clinical trials, promotes sociability in mice due to its 5-HT releasing properties in the NAc. Here, we systematically evaluated the ability of MDMA and a selective 5-HT1b receptor agonist to rescue sociability deficits in multiple different mouse models for ASD. We find that MDMA administration enhances sociability in control mice and reverses sociability deficits in all four ASD mouse models examined, whereas administration of a 5-HT1b receptor agonist selectively rescued the sociability deficits in all six mouse models for ASD. These preclinical findings suggest that pharmacological enhancement of 5-HT release or direct 5-HT1b receptor activation may be therapeutically efficacious in ameliorating some of the core sociability deficits present across etiologically distinct presentations of ASD.

Effects of the Selective Serotonin Reuptake Inhibitor Fluoxetine on Developing Neural Circuits in a Model of the Human Fetal Cortex

The developing prenatal brain is particularly susceptible to environmental disturbances. During prenatal brain development, synapses form between neurons, resulting in neural circuits that support complex cognitive functions. In utero exposure to environmental factors such as pharmaceuticals that alter the process of synapse formation increases the risk of neurodevelopmental abnormalities. However, there is a lack of research into how specific environmental factors directly impact the developing neural circuitry of the human brain. For example, selective serotonin reuptake inhibitors are commonly used throughout pregnancy to treat depression, yet their impact on the developing fetal brain remains unclear. Recently, human brain models have provided unprecedented access to the critical window of prenatal brain development. In the present study, we used human neurons and cortical spheroids to determine whether the selective serotonin reuptake inhibitor fluoxetine alters neurite and synapse formation and the development of spontaneous activity within neural circuits. We demonstrate that cortical spheroids express serotonin transporter, thus recapitulating the early developmental expression of serotonin transporter associated with cortical pyramidal neurons. Cortical spheroids also appropriately express serotonin receptors, such as synaptic 5-HT2A and glial 5-HT5A. To determine whether fluoxetine can affect developing neural circuits independent of serotonergic innervation from the dorsal and medial raphe nuclei, we treated cortical neurons and spheroids with fluoxetine. Fluoxetine alters neurite formation in a dose-dependent fashion. Intriguingly, in cortical spheroids, neither acute nor chronic fluoxetine significantly altered excitatory synapse formation. However, only acute, but not chronic fluoxetine exposure altered inhibitory synaptogenesis. Finally, fluoxetine reversibly suppresses neuronal activity in a dose-dependent manner. These results demonstrate that fluoxetine can acutely alter synaptic function in developing neural circuits, but the effects were not long-lasting. This work provides a foundation for future studies to combine serotonergic innervation with cortical spheroids and assess the contributions of fluoxetine-induced alterations in serotonin levels to brain development.

Residual effects of abomasal 5-hydroxytryptophan administration on serotonin metabolism in cattle

Studies of serotonin in animal husbandry has received growing interest. However, there is limited information about serotonin manipulation using 5-HTP administered postruminally and its residual effects in cattle. The objective of this study was to evaluate the effectiveness of 5-HTP infused into the abomasum for enhancing circulating serotonin in cattle. Four Holstein steers (487 ± 7.6 kg) fitted with ruminal cannulas were used in a 4 × 4 Latin Square design experiment. The treatments were intra-abomasal infusion of 5-HTP at 0, 0.25, 0.5, and 1 mg/kg BW. Blood was collected from the jugular vein of each steer at -60, -30, 0, 30, 60, 120, 240, and 480 min from 5-HTP infusion for basal and short term evaluation and, at 1, 2, 4, and 7 d after 5-HTP infusion for long term evaluation. Dry matter intake was not affected (P > 0.05) by intra-abomasal infusions. The half-life of 5-HTP was dose-independent (128 min). The serum 5-HTP, serotonin, and 5-hydroxyindoleacetic acid area under the curve increased (P < 0.05) linearly with an increased dose of 5-HTP. Serum 5-HTP reached peak concentration in approximately 30 min after dosing while serum and plasma serotonin peaked after 240 min postinfusion. Serotonin was greater than control for all 5-HTP doses 1 d and 2 d after infusion in serum and plasma, respectively. Intra-abomasal infusion of 5-HTP at doses up to 1 mg/ kg BW increases circulating serotonin for up 2 days.

5-HT7 receptor activation rescues impaired synaptic plasticity in an autistic-like rat model induced by prenatal VPA exposure

Autism spectrum disorder (ASD) is a severe life-long neuropsychiatric disorder. Alterations and imbalance of several neurochemical systems may be involved in ASD pathophysiology, of them, serotonergic neurotransmission dysfunction and deficiency may underlie behavioral abnormalities associated with ASD. However, the functional importance of serotonergic receptors, particularly 5HT7 receptors in ASD pathology remains poorly defined. Serotonin receptor subtype 7 (5-HT7R) plays a direct regulatory role in the development and also for the mature function of the brain, therefore, further studies are necessary to elucidate the role of these receptors in the etiology of autism. To address this issue, we combined here behavioral, electrophysiological methods to further characterize the contribution of 5-HT7Rs in the prenatal valproic acid (VPA) exposure-induced impairment in synaptic plasticity and their impact on the associated behavioral changes. This may help to unravel the underlying cellular mechanisms involved in ASD and can lead to new treatment and/or prevention therapies based on the role of the serotonergic system for autism. Findings revealed that compared to control, autistic-like offspring showed increased anxiety-like behavior, reduced social interaction, decreased locomotor activity, and impaired identification of the novel object. However, administration of 5-HT7Rs agonist, LP-211, for 7 consecutive days before testing from postnatal day 21 to 27 reversed all behavioral deficits induced by prenatal exposure to VPA in offspring. Also, both short-term depression and long-term potentiation were impaired in the autistic-like pups, but activation of 5-HT7Rs rescued the LTP impairment in the autistic-like group so that there was no significant difference between the two groups. Blockade of 5-HT7Rs caused LTP impairment following HFS in the autistic-like group. Besides, there was a significant difference in LTD induction following SB-269970 application between the control and the autistic-like groups measured at first 10 min following TPS. Moreover, both the number and the size of retrograde fast blue-labelled neurons in the raphe nuclei were reduced. Overall, these results provide for the first time, as far as we know, functional evidence for the restorative role of 5-HT7Rs activation against prenatal VPA exposure induced behavioral deficits and hippocampal synaptic plasticity impairment. Therefore, these receptors could be a potential and promising pharmacotherapy target for the treatment of autism.

The Nrf2 pathway in psychiatric disorders: pathophysiological role and potential targeting

Introduction: All psychiatric disorders exhibit excitotoxicity, mitochondrial dysfunction, inflammation, oxidative stress, and neural damage as their common characteristic. The endogenous nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is implicated in the defense mechanism against oxidative stress and has a significant role in psychiatric disorders.Areas covered: We explore the role of Nrf2 pathway and its modulators in psychiatric disorders. The literature was searched utilizing various databases such as Embase, Medline, Web of Science, Pub-Med, and Google Scholar from 2010 to 2020. The search included research articles, clinical reports, systematic reviews, and meta-analyses.Expert opinion: Environmental factors and genetic predisposition can be a trigger for the development of psychiatric disorders. Nrf2 downregulates certain inflammatory pathways and upregulates various antioxidant enzymes to maintain a balance. However, its intricate balance with NF-Kβ (Nuclear factor kappa light chain enhancer of activated B cells) and its crosstalk with the transcription factor Nrf2 is critical in severe oxidative stress. Several Nrf2 modulators are now in clinical trials and can help reduce oxidative stress and neuroinflammation. There are immense potential opportunities for these modulators to become a novel therapeutic option.

Daily intake of Lactobacillus alleviates autistic-like behaviors by ameliorating the 5-hydroxytryptamine metabolic disorder in VPA-treated rats during weaning and sexual maturation

Probiotic therapy targeting gut-brain axis has been proven to be effective in treating autistic patients. The present study aimed to assess the ability of three Lactobacillus strains (L. helveticus CCFM1076, L. acidophilus La28, and L. acidophilus JCM 1132) to alleviate autistic-like behavioral symptoms in VPA-treated rats from weaning to sexual maturation. For the first time, we assessed the synthesis of 5-hydroxytryptamine (5HT) and the metabolic capacity of the 5HT system in the peripheral and central nervous systems (PNS and CNS, respectively) based on tryptophan metabolism based on VPA-induced autism model. We also assessed gut microbiota, and short-chain fatty acids (SCFAs) at the end of week 8. While improving autistic-like behavioral symptoms, we found L. helveticus CCFM1076 was more beneficial in regulating 5HT anabolism and catabolism, balancing excitatory and inhibitory neurotransmitter release in the PNS and CNS, and increasing oxytocin (OT) synthesis in the hypothalamus. A significant correlation was noted between 5HT levels and the release of GABA, glutamate (Glu), and OT, suggesting that 5HT plays a vital role in the neuroendocrine network. Analyses of the gut microbiota and SCFA levels revealed greater Turicibacter abundance and lower butyric acid levels in VPA-treated rats, which have been reported to be associated with 5HT levels. L. helveticus CCFM1076 helped reduce Turicibacter abundance and up-regulate butyric acid levels, while L. acidophilus La28 and L. acidophilus JCM 1132 did not. L. helveticus CCFM1076 restored neurotransmitter homeostasis by improving the balance of the 5HT system in the PNS and CNS, thereby ameliorating autistic-like behaviors. This finding will help in the development of bioproducts for treating autism and in the establishment of a treatment model mimicking the intestinal environment of autistic patients.

5-Hydroxytryptophan strongly stimulates serotonin synthesis in Holstein steers

Although serotonin has been extensively studied in many species, there is a lack of information in ruminants, and no research has been evaluated if its precursor, 5-hydroxytryptophan (5-HTP), administered into the abomasum may be used as a means to manipulate serotonin metabolism. Thus, the objective of this study was to evaluate if intra-abomasal infusion of 5-HTP increases circulating serotonin in the steer. Eight Holstein steers (471 ± 8.9 kg) were used in a replicated 4 × 4 Latin Square design experiment. The treatments were intra-abomasal infusion of 5-HTP at 0.5, 1, 2.5, and 5 mg/kg BW. Blood was collected at 0, 2, 4, 6, 8, and 24 h after infusion. The serum concentration of 5-HTP increased quadratically (P = 0.005) with a peak at 2 h after administration. The 5-HTP administration increased (P < 0.05) serum serotonin in comparison with baseline with no difference (P > 0.05) between the doses of 5-HTP. When 5-HTP was dosed at 2.5 mg/kg BW or higher, intake decreased, and there was an altered manure consistency. The serum 5-hydroxyindole acetic acid concentrations followed the same pattern as 5-HTP. Plasma glucose content was not affected (P > 0.05) by 5-HTP dosing. However, free fatty acids concentration in the plasma was lower (P > 0.05) compared with baseline for the infusion levels of 0.5 and 1 mg/kg BW. Intra-abomasal infusion of 5-HTP efficiently increases serum serotonin cattle.

Markers for the central serotonin system correlate to verbal ability and paralinguistic social voice processing in autism spectrum disorder

Impairment in verbal communication abilities has been reported in autism spectrum disorder (ASD). Dysfunction of the serotonergic system has also been reported in ASD. However, it is still unknown how the brain serotonergic system relates to impairment in verbal communication abilities in individuals with ASD. In the present study, we investigated the correlation between brain serotonergic condition and brain sensitivity to paralinguistic stimuli (i.e., amplitude in the human voice prosodic change-evoked mismatch field) measured by magnetoencephalography (MEG) or verbal ability in 10 adults with ASD. To estimate the brain serotonergic condition, we measured the serotonin transporter nondisplaceable binding potential cerebrum-wide using positron emission tomography with [11C]N,N-dimethyl-2-(2-amino-4-cyanophenylthio)benzylamine ([11C] DASB). The results demonstrated a significant positive correlation between brain activity to paralinguistic stimuli and brain serotonin transporter binding potential in the left lingual gyrus, left fusiform gyrus and left calcarine cortex. In addition, there were significant positive correlations between verbal ability and serotonergic condition in the right anterior insula, right putamen and right central operculum. These results suggested that the occipital cortex is implicated in recognition of the prosodic change in ASD, whereas the right insula-involved serotonergic system is important in nurturing verbal function in ASD.Trial registration: UMIN000011077.

Pain in neuropsychiatry: Insights from animal models

Pain is the most common symptom reported in clinical practice, meaning that it is associated with many pathologies as either the origin or a consequence of other illnesses. Furthermore, pain is a complex emotional and sensorial experience, as the correspondence between pain and body damage varies considerably. While these issues are widely acknowledged in clinical pain research, until recently they have not been extensively considered when exploring animal models, important tools for understanding pain pathophysiology. Interestingly, chronic pain is currently considered a risk factor to suffer psychiatric disorders, mainly stress-related disorders like anxiety and depression. Conversely, pain appears to be altered in many psychiatric disorders, such as depression, anxiety and schizophrenia. Thus, pain and psychiatric disorders have been linked in epidemiological and clinical terms, although the neurobiological mechanisms involved in this pathological bidirectional relationship remain unclear. Here we review the evidence obtained from animal models about the co-morbidity of pain and psychiatric disorders, placing special emphasis on the different dimensions of pain.

Molecular Biomarkers Predictive of Sertraline Treatment Response in Young Children With Autism Spectrum Disorder

Sertraline is one among several selective serotonin reuptake inhibitors (SSRIs) that exhibited improvement of language development in Autism Spectrum Disorder (ASD); however, the molecular mechanism has not been elucidated. A double blind, randomized, 6-month, placebo-controlled, clinical trial of low-dose sertraline in children ages (3–6 years) with ASD was conducted at the UC Davis MIND Institute. It aimed at evaluating the efficacy and benefit with respect to early expressive language development and global clinical improvement. This study aimed to identify molecular biomarkers that might be key players in the serotonin pathway and might be predictive of a clinical response to sertraline. Fifty eight subjects with the diagnosis of ASD were randomized to sertraline or placebo. Eight subjects from the sertraline arm and five from the placebo arm discontinued from the study. Furthermore, four subjects did not have a successful blood draw. Hence, genotypes for 41 subjects (20 on placebo and 21 on sertraline) were determined for several genes involved in the serotonin pathway including the serotonin transporter-linked polymorphic region (5-HTTLPR), the tryptophan hydroxylase 2 (TPH2), and the Brain-Derived Neurotrophic Factor (BDNF). In addition, plasma levels of BDNF, Matrix metallopeptidase 9 (MMP-9) and a selected panel of cytokines were determined at baseline and post-treatment. Intent-to-treat analysis revealed several primary significant correlations between molecular changes and the Mullen Scales of Early Learning (MSEL) and Clinical Global Impression Scale – Improvement (CGI-I) of treatment and control groups but they were not significant after adjustment for multiple testing. Thus, sertraline showed no benefit for treatment of young children with ASD in language development or changes in molecular markers in this study. These results indicate that sertraline may not be beneficial for the treatment of children with ASD; however, further investigation of larger groups as well as longer term follow-up studies are warranted.

Serotonergic innervation of the amygdala is increased in autism spectrum disorder and decreased in Williams syndrome

BACKGROUND

Williams syndrome (WS) and autism spectrum disorder (ASD) are neurodevelopmental disorders that demonstrate overlapping genetic associations, dichotomous sociobehavioral phenotypes, and dichotomous pathological differences in neuronal distribution in key social brain areas, including the prefrontal cortex and the amygdala. The serotonergic system is critical to many processes underlying neurodevelopment and is additionally an important neuromodulator associated with behavioral variation. The amygdala is heavily innervated by serotonergic projections, suggesting that the serotonergic system is a significant mediator of neuronal activity. Disruptions to the serotonergic system, and atypical structure and function of the amygdala, are implicated in both WS and ASD.

METHODS

We quantified the serotonergic axon density in the four major subdivisions of the amygdala in the postmortem brains of individuals diagnosed with ASD and WS and neurotypical (NT) brains.

RESULTS

We found opposing directions of change in serotonergic innervation in the two disorders, with ASD displaying an increase in serotonergic axons compared to NT and WS displaying a decrease. Significant differences (p < 0.05) were observed between WS and ASD data sets across multiple amygdala nuclei.

LIMITATIONS

This study is limited by the availability of human postmortem tissue. Small sample size is an unavoidable limitation of most postmortem human brain research and particularly postmortem research in rare disorders.

CONCLUSIONS

Differential alterations to serotonergic innervation of the amygdala may contribute to differences in sociobehavioral phenotype in WS and ASD. These findings will inform future work identifying targets for future therapeutics in these and other disorders characterized by atypical social behavior.

The Regulation of Reactive Neuroblastosis, Neuroplasticity, and Nutraceuticals for Effective Management of Autism Spectrum Disorder

Autism spectrum disorder (ASD) encompasses a cluster of neurodevelopmental and genetic disorders that has been characterized mainly by social withdrawal, repetitive behavior, restricted interests, and deficits in language processing mainly in children. ASD has been known to severely impair behavioral patterns and cognitive functions including learning and memory due to defects in neuroplasticity. The biology of the ASD appears to be highly complex and heterogeneous, and thus, finding a therapeutic target for autism remains obscure. There has been no complete prevention or disease-modifying cure for this disorder. Recently, individuals with autism have been characterized by reactive neurogenesis, obstructions in axonal growth, heterotopia, resulting from dysplasia of neuroblasts in different brain regions. Therefore, it can be assumed that the aforementioned neuropathological correlates seen in the autistic individuals might originate from the defects mainly in the regulation of neuroblasts in the developing as well as adult brain. Nutrient deficiencies during early brain development and intake of certain allergic foods have been proposed as main reasons for the development of ASD. However, the integrated understanding of neurodevelopment and functional aspects of neuroplasticity working through neurogenesis in ASD is highly limited. Moreover, neurogenesis at the level of neuroblasts can be regulated by nutrition. Hence, defects in neuroblastosis underlying the severity of autism potentially could be rectified by appropriate implementation of nutraceuticals.

Association of human serotonin receptor 4 promoter methylation with autism spectrum disorder

Human serotonin receptor 4 (HTR4) encodes a 5-HT4 receptor involved in learning, memory, depression, anxiety, and feeding behavior. The aim of this study was to investigate the association between the deoxyribonucleic acid (DNA) methylation of HTR4 promoter and autism spectrum disorder (ASD), a disease characterized by communication disorder and repetitive or restrictive behavior.Peripheral blood DNA was obtained from 61 ASD children and 66 healthy children, and the DNA methylation of HTR4 promoter was assessed by quantitative methylation-specific polymerase chain reaction. We used percentage of methylated reference (PMR) to represent DNA methylation level.Due to significant age differences between ASD cases and controls (3 [2, 5] years and 6 [5, 6] years, P = 3.34E-10), we used binary logistic regression analysis for adjustment. Our results showed that the DNA methylation levels of HTR4 promoter were significantly lower in children with ASD than in healthy children (median PMR: 66.23% vs 94.31%,P = .028, age-adjusted P = .034). In addition, the DNA methylation of HTR4 promoter was inversely associated with age in male ASD cases (total cases: r = -0.283, P = .027; male cases: r = -0.431, P = .002; female cases: r = -0.108, P = .752). Dual-luciferase reporter gene assay showed that the reporter gene expression in the strain with recombinant pGL3-promoter-HTR4 plasmid was significantly higher than that in the strain with pGL3-promoter plasmid (fold change = 2.01, P = .0065), indicating that the HTR4 promoter fragment may contain transcription factors to upregulate promoter activity.Our study suggested that hypomethylation of the HTR4 promoter is a potential biomarker for predicting the risk of male ASD.

Serotonin transporter deficiency alters socioemotional ultrasonic communication in rats

It has been widely established that serotonin plays important role in the regulation of emotional and social behaviour. Rodents with a genetic deletion of the serotonin reuptake transporter (SERT) are used as a model to study lifelong consequences of increased extracellular 5‐HT levels due to its impaired reuptake. SERT knock-out (SERT-KO) mice and rats consistently showed anxiety-like symptoms and social deficits. Nevertheless, the impact of SERT deletion on socioemotional ultrasonic communication has not been addressed. Here we investigated the impact of lifelong serotonin abundance on ultrasonic vocalisation accompanying social interactions and open field exploration in rats. SERT-KO rats displayed reduced overall duration of social contacts, but increased time spent on following the conspecific. The altered pattern of social behaviour in SERT-KO rats was accompanied by the structural changes in ultrasonic vocalisations, as they differed from their controls in distribution of call categories. Moreover, SERT deletion resulted in anxiety-like behaviours assessed in the open field test. Their anxious phenotype resulted in a lower tendency to emit appetitive 50-kHz calls during novelty exploration. The present study demonstrates that genetic deletion of SERT not only leads to the deficits in social interaction and increased anxiety but also affects ultrasonic communication.

Vortioxetine Reduces Marble Burying but Only Transiently Enhances Social Interaction Preference in Adult Male BTBR T+Itpr3tf/J Mice

Vortioxetine is a multimodal antidepressant with agonist activity at serotonin (5-HT)_1A and 5-HT_1B receptors that blocks the 5-HT transporter (SERT). Previously in male BTBR T⁺Itpr3^tf/J (BTBR) mice, the 5-HT_1A partial agonist buspirone and SERT blocker fluoxetine enhanced social interaction but did not reduce marble burying. We hypothesized that vortioxetine through its actions at SERT and 5-HT_1A could improve BTBR sociability and via 5-HT_1B could reduce burying better than sertraline, a selective SERT blocker. Vortioxetine (5-10 mg/kg) or sertraline (2 mg/kg) was administered 30 min presociability and 75 min prior to marble burying tests. Vortioxetine (10 mg/kg) occupancy (%) was 84 ± 1 for SERT, 31 ± 12 for 5-HT_1A, and 80 ± 5 for 5-HT_1B in brain at 110 min postinjection, and serum oxytocin was 24% lower (p < 0.01) in vortioxetine-treated mice. Vortioxetine reduced novel object investigation, whereas sertraline enhanced overall sociability. However, the vortioxetine-induced increase in social sniffing was transient, as it was lost with 60-120 min presociability test delays in subsequent experiments. Vortioxetine and sertraline both reduced BTBR marble burying. Based on vortioxetine occupancy, actions at SERT and/or 5-HT_1B are more likely to underlie its behavioral effects than 5-HT_1A. Overall, vortioxetine has great potential for suppressing restrictive-repetitive behaviors, but it appears less promising as a sociability enhancer.

Effects of Acute Tryptophan Depletion on Repetitive Behavior in Laying Hens

Repetitive pecking at the feather cover of other birds (FP) is one of the most important welfare problems in domestic birds. It is not only characterized by motor symptoms, but also by an innate vulnerability of the serotonergic system. Moreover, the serotonergic system influences cognitive function. Acute tryptophan depletion (ATD) is a widely used method for studying serotonergic function in mammals and has been recently validated in birds. However, a tryptophan-deficient amino acid mixture has never been tested on groups of birds to impact their social behavior, including repetitive feather pecking, nor has it been given to potentially impact their cognition and motor performance. One hundred and sixty White Leghorn laying hens consisting of two genetic lines divergently selected to perform high (H) or low (L) levels of FP, and an unselected control line (UC), were kept in 10 groups consisting of 4 H, 3 L, and 9 UC genotypes. In a counterbalanced order, half of the groups were first subjected to an ATD treatment, while the other half were first given a balanced control (BC) treatment, and vice versa, after which their feather pecking behavior was observed. The effect of ATD/BC on repetitive pecking, motor performance, and cognition was investigated in a 5-s delayed reward task in an operant chamber with 10 phenotypic feather peckers, 10 recipients of feather pecking, and 10 bystanders (who neither performed nor received feather pecks). ATD given to groups of birds induced gentle, repetitive feather pecking in all genotypes. Following ATD, phenotypic feather peckers performed more poorly during the delayed reward task, as seen by their higher number of repetitive, non-rewarded key, and non-key pecks in the operant chamber. In conclusion, ATD impacted the hens' social behavior by increasing the number of repetitive gentle feather pecks at conspecifics. Furthermore, feather peckers were more likely to peck while waiting for a reward after ATD, suggesting a role for the serotonergic system on cognition in these birds.

Comparison of the effects of perceptual-motor exercises, vitamin D supplementation and the combination of these interventions on decreasing stereotypical behavior in children with autism disorder

OBJECTIVES

The aim of this study was to examine the combined effects of perceptual-motor exercises and vitamin D3 supplementation on the reduction of stereotypical behavior in children with autism spectrum disorder (ASD).

METHODS

In this study, 100 eligible children with age ranging from 6 to 9 years were randomly selected and divided into four groups: Group A-perceptual-motor exercises (n = 25); Group B-25-hydroxycholecalciferol (25 (OH) D) (n = 25); Group C-perceptual-motor exercises and 25 (OH) D (n = 25); and Group D-control (n = 25).

RESULTS

The stereotypes decreased from elementary level, 17% in Group A, 13% in Group B and 28% in Group C among the participants. There was no change in the stereotypical in the control group during the interventions. Also, the stereotypes in Group C showed the highest decrease, compared to the other three groups.

CONCLUSIONS

We concluded that combination of perceptual-motor exercises and vitamin D3 supplementation in children with ASD leads to significant reduction in their stereotypic behaviors.

Serotonin and serotonin transporter levels in autistic children

OBJECTIVES

To assess the possible correlation between serotonin and serotonin transporter (SERT) with the autism severity and investigate the association between these parameters in autistic children to assess their possible role for diagnosis of autism severity.

METHODS

A comparative cross-sectional study was carried out in the Chemistry and Biochemistry Department, College of Medicine, Al-Nahrain University, Baghdad, Iraq while the samples were taken from 60 male autistic children recruited to the Department of Pediatrics at Al-Sader Hospital, Baghdad, Iraq between November 2014 amd April 2015. Levels of serotonin and serotonin transporters (SERT) were determined in 60 male autistic Iraqi patients classified into mild, moderate and severe (20 for each). These levels were compared with those of 26 healthy control children. Results: Levels of serotonin and SERT were significantly increased in autistic children than that of gender and age-matched controls. Serotonin levels were 80.63± 21.83 ng/ml in mild, 100.39±23.07 ng/ml moderate, and 188.7±31.72 ng/ml severe autistic patients. Serotonin transporter levels were 10.13±4.51 ng/ml in mild, 13.15±4.71 ng/ml moderate, and 16.32±6.7 ng/ml in  severe autistic patients. The increase of both serotonin and SERT levels were associated with severity of autism. Receiver operating characteristic (ROC) analysis  can be used for diagnostic and prognostic purposes.

CONCLUSIONS

High serotonin and SERT levels may indicate that these biomarkers have a role in the autism pathogenesis and support the possibility of using serotonin and SERT to diagnose autism severity.

Why is vitamin B6 effective in alleviating the symptoms of autism?

Many factors are reported to be involved in the complex pathophysiological processes of autism, suggesting that there is considerable variability in the manifestations of this disease. Several interventions are used to treat this disorder. Among them, vitamin B6 is widely used to treat the symptoms observed in autism. Vitamin B6 is beneficial for about half of autistic individuals in decreasing behavioral problems. However, until now, it remains unknown why vitamin B6 is effective for this disease. Although the exact pathogenesis is not defined, it is evident that certain neurotransmitter systems are impaired in the brains of autistic patients, causing the symptoms observed in the disease. In fact, impairment of many neurotransmitter systems has been reported, including GABA, serotonin, dopamine, and noradrenalin. Furthermore, vitamin B6 is important for the synthesis of many neurotransmitters, including GABA, serotonin, dopamine, noradrenalin, histamine, glycine, and d-serine, indicating that vitamin B6 supplementation may enhance many neurotransmitter systems. Thus, vitamin B6 supplementation can treat the impaired neurotransmitter systems in a given patient, even if the actual impaired neurotransmitter systems are not defined in that patient.

Evidence of a Conserved Molecular Response to Selection for Increased Brain Size in Primates

The adaptive significance of human brain evolution has been frequently studied through comparisons with other primates. However, the evolution of increased brain size is not restricted to the human lineage but is a general characteristic of primate evolution. Whether or not these independent episodes of increased brain size share a common genetic basis is unclear. We sequenced and de novo assembled the transcriptome from the neocortical tissue of the most highly encephalized nonhuman primate, the tufted capuchin monkey (Cebus apella). Using this novel data set, we conducted a genome-wide analysis of orthologous brain-expressed protein coding genes to identify evidence of conserved gene–phenotype associations and species-specific adaptations during three independent episodes of brain size increase. We identify a greater number of genes associated with either total brain mass or relative brain size across these six species than show species-specific accelerated rates of evolution in individual large-brained lineages. We test the robustness of these associations in an expanded data set of 13 species, through permutation tests and by analyzing how genome-wide patterns of substitution co-vary with brain size. Many of the genes targeted by selection during brain expansion have glutamatergic functions or roles in cell cycle dynamics. We also identify accelerated evolution in a number of individual capuchin genes whose human orthologs are associated with human neuropsychiatric disorders. These findings demonstrate the value of phenotypically informed genome analyses, and suggest at least some aspects of human brain evolution have occurred through conserved gene–phenotype associations. Understanding these commonalities is essential for distinguishing human-specific selection events from general trends in brain evolution.

Oxytocin effects on emotional response to others' faces via serotonin system in autism: A pilot study

The oxytocin (OT)-related serotonergic system is thought to play an important role in the etiology and social symptoms of autism spectrum disorder (ASD). However, no evidence exists for the relation between the prosocial effect of chronic OT administration and the brain serotonergic system. Ten male subjects with ASD were administered OT for 8-10 weeks in an open-label, single-arm, non-randomized, uncontrolled manner. Before and during the OT treatment, positron emission tomography was used with the (¹¹C)-3-amino-4-(2-[(demethylamino)methyl]phenylthio)benzonitrile(¹¹C-DASB) radiotracer. Then binding of serotonin transporter (¹¹C-DASB BP_ND) was estimated. The main outcome measures were changes in ¹¹C-DASB BP_ND and changes in the emotional response to others' faces. No significant change was found in the emotional response to others' faces after the 8-10 week OT treatment. However, the increased serotonin transporter (SERT) level in the striatum after treatment was correlated significantly with increased negative emotional response to human faces. This study revealed a relation between changes in the serotonergic system and in prosociality after chronic OT administration. Additional studies must be conducted to verify the chronic OT effects on social behavior via the serotonergic system.

Increased serum serotonin improves parturient calcium homeostasis in dairy cows

Hypocalcemia in dairy cows is caused by the sudden increase in calcium demand by the mammary gland for milk production at the onset of lactation. Serotonin (5-HT) is a key factor for calcium homeostasis, modulating calcium concentration in blood. Therefore, it is hypothesized that administration of 5-hydroxy-l-tryptophan (5-HTP), a 5-HT precursor, can increase 5-HT concentrations in blood and, in turn, induce an increase in blood calcium concentration. In this study, 20 Holstein dairy cows were randomly assigned to 2 experimental groups. Both groups received a daily i.v. infusion of 1 L of either 0.9% NaCl (C group; n = 10) or 0.9% NaCl containing 1 mg of 5-HTP/kg of BW (5-HTP group, n = 10). Infusions started d 10 before the estimated parturition and ceased the day of parturition, resulting in at least 4 d of infusion (8.37 ± 0.74 d of infusion). Until parturition, blood samples were collected every morning before the infusions, after parturition samples were taken daily until d 7, and a final sample was collected on d 30. Milk yield was recorded during this period. No differences between groups were observed for blood glucose, magnesium, and β-hydroxybutyrate. Cows receiving the 5-HTP infusion showed an increase in fatty acid concentrations from d -3 to -1 before parturition. Serum 5-HT concentrations were increased at d -4 related to parturition until d 5 postpartum in the 5-HTP group compared with the C group. In addition, cows from the 5-HTP group had increased 5-HT concentrations in colostrum, but not in mature milk, on d 7 postpartum. Serum calcium concentrations decreased in both groups around parturition; however, calcium remained higher in the 5-HTP group than in controls, with a significant difference between groups on d 1 (1.62 ± 0.08 vs. 1.93 ± 0.09 mmol/L in control and 5-HTP groups, respectively) and d 2 (1.83 ± 0.06 vs. 2.07 ± 0.07 mmol/L in control and 5-HTP groups, respectively). Additionally, colostrum yield (first milking) was lower in the 5-HTP group compared with the C group, but without consequences on colostrum IgG concentrations. Milk yield did not differ between groups during the rest of the experiment. The study data were consistent with the concept that infusion of 5-HTP to dairy cows increases blood 5-HT concentrations, which in turn is a significant regulatory component in the chain of effectors that affect calcium status around parturition, hence the occurrence of clinical or subclinical hypocalcemia.

Prenatal exposure to antidepressants and risk of epilepsy in childhood

PURPOSE

This study aimed to estimate the association between prenatal exposure to antidepressants and risk of epilepsy in childhood, taking maternal depression into account.

METHODS

We conducted a population-based cohort study including all Danish singletons born alive between 1997 and 2008 (n = 734 237). Information on antidepressant medication and diagnosis of depression and epilepsy was obtained from Danish National Registers. The exposed group comprised children of mothers who used antidepressants from 30 days before pregnancy until the date of birth. The reference group comprised children of mothers who used no antidepressants from 6 months before pregnancy to birth. We estimated the hazard ratios (HR) of epilepsy and 95% confidence intervals (CI) using Cox proportional hazard models.

RESULTS

We identified 12 438 (1.7%) children exposed to antidepressants during pregnancy (including 30 days before pregnancy) and 5829 (0.8%) children diagnosed with epilepsy in the follow-up time (mean: 6.7 years). Children exposed to antidepressants during pregnancy had a 27% higher risk of epilepsy (aHR: 1.27; 95%CI: 1.05-1.54) than children in the reference group. The estimate of this association was 1.71 (95%CI: 1.10-2.66) if their mothers also had a registry-based hospital diagnosis of depression in the 6 months before pregnancy or during pregnancy and 1.14 (95%CI: 0.91-1.43) if their mothers had no registry-based hospital diagnosis of depression. Children of mothers who used antidepressants from 2 to 6 months before pregnancy (but not during pregnancy) had an increased risk of epilepsy (aHR: 1.36; 95%CI: 1.07-1.73).

CONCLUSIONS

Antidepressant use during pregnancy was associated with a higher risk of epilepsy among children whose mothers had also a registry-based hospital diagnosis of depression during pregnancy. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of prenatal maternal stress on serotonin and fetal development

Fetuses are exposed to many environmental perturbations that can influence their development. These factors can be easily identifiable such as drugs, chronic diseases or prenatal maternal stress. Recently, it has been demonstrated that the serotonin synthetized by the placenta was crucial for fetal brain development. Moreover, many studies show the involvement of serotonin system alteration in psychiatric disease during childhood and adulthood. This review summarizes existing studies showing that prenatal maternal stress, which induces alteration of serotonin systems (placenta and fetal brain) during a critical window of early development, could lead to alteration of fetal development and increase risks of psychiatric diseases later in life. This phenomenon, termed fetal programming, could be moderated by the sex of the fetus. This review highlights the need to better understand the modification of the maternal, placental and fetal serotonin systems induced by prenatal maternal stress in order to find early biomarkers of psychiatric disorders.

Merging data from genetic and epigenetic approaches to better understand autistic spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is characterized by a wide range of cognitive and behavioral abnormalities. Genetic research has identified large numbers of genes that contribute to ASD phenotypes. There is compelling evidence that environmental factors contribute to ASD through influences that differentially impact the brain through epigenetic mechanisms. Both genetic mutations and epigenetic influences alter gene expression in different cell types of the brain. Mutations impact the expression of large numbers of genes and also have downstream consequences depending on specific pathways associated with the mutation. Environmental factors impact the expression of sets of genes by altering methylation/hydroxymethylation patterns, local histone modification patterns and chromatin remodeling. Herein, we discuss recent developments in the research of ASD with a focus on epigenetic pathways as a complement to current genetic screening.

Inverse Effect of Fluoxetine on Medial Prefrontal Cortex Activation During Reward Reversal in ADHD and Autism

Attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) share brain function abnormalities during cognitive flexibility. Serotonin is involved in both disorders, and selective serotonin reuptake inhibitors (SSRIs) can modulate cognitive flexibility and improve behavior in both disorders. Thus, this study investigates shared and disorder-specific brain dysfunctions in these 2 disorders during reward reversal, and the acute effects of an SSRI on these. Age-matched boys with ADHD (15), ASD (18), and controls (21) were compared with functional magnetic resonance imaging (fMRI) during a reversal task. Patients were scanned twice, under either an acute dose of Fluoxetine or placebo in a double-blind, placebo-controlled randomized design. Repeated-measures analyses within patients assessed drug effects. Patients under each drug condition were compared with controls to assess normalization effects. fMRI data showed that, under placebo, ASD boys underactivated medial prefrontal cortex (mPFC), compared with control and ADHD boys. Both patient groups shared decreased precuneus activation. Under Fluoxetine, mPFC activation was up-regulated and normalized in ASD boys relative to controls, but down-regulated in ADHD boys relative to placebo, which was concomitant with worse task performance in ADHD. Fluoxetine therefore has inverse effects on mPFC activation in ASD and ADHD during reversal learning, suggesting dissociated underlying serotonin abnormalities.

Inverse fluoxetine effects on inhibitory brain activation in non-comorbid boys with ADHD and with ASD

RATIONALE

Attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are often comorbid and have both performance and brain dysfunctions during motor response inhibition. Serotonin agonists modulate motor response inhibition and have shown positive behavioural effects in both disorders.

AIMS

We therefore used functional magnetic resonance imaging (fMRI) to investigate the so far unknown shared and disorder-specific inhibitory brain dysfunctions in these two disorders, as well as the effects of a single dose of the selective serotonin reuptake inhibitor fluoxetine.

METHODS

Age-matched boys with ADHD (18), ASD (19) and healthy controls (25) were compared with fMRI during a stop task measuring motor inhibition. Patients were scanned twice, under either an acute dose of fluoxetine or placebo in a double-blind, placebo-controlled randomised design. Repeated measures analyses within patients assessed drug effects. To test for potential normalisation effects of brain dysfunctions, patients under each drug condition were compared to controls.

RESULTS

Under placebo, relative to controls, ASD boys showed overactivation in left and right inferior frontal cortex (IFC), while ADHD boys showed disorder-specific underactivation in orbitofrontal cortex (OFC) and basal ganglia. Under fluoxetine, the prefrontal dysfunctions were no longer observed, due to inverse effects of fluoxetine on these activations: fluoxetine downregulated IFC and OFC activation in ASD but upregulated them in ADHD.

CONCLUSIONS

The findings show that fluoxetine normalises frontal lobe dysfunctions in both disorders via inverse effects, downregulating abnormally increased frontal activation in ASD and upregulating abnormally decreased frontal activation in ADHD, potentially reflecting inverse baseline serotonin levels in both disorders.

Association of the FGA and SLC6A4 genes with autistic spectrum disorder in a Korean population

BACKGROUND

Autism spectrum disorder (ASD) is a neurobiological disorder characterized by distinctive impairments in cognitive function, language, and behavior. Linkage and population studies suggest a genetic association between solute carrier family 6 member 4 (SLC6A4) variants and ASD.

METHOD

Logistic regression was used to identify associations between single-nucleotide polymorphisms (SNPs) and ASD with 3 alternative models (additive, dominant, and recessive). Linear regression analysis was performed to determine the influence of SNPs on Childhood Autism Rating Scale (CARS) scores as a quantitative phenotype.

RESULTS

In the present study, we examined the associations of SNPs in the SLC6A4 gene and the fibrinogen alpha chain (FGA) gene. Logistic regression analysis showed a significant association between the risk of ASD and rs2070025 and rs2070011 in the FGA gene. The gene-gene interaction between SLC6A4 and FGA was not significantly associated with ASD susceptibility. However, polymorphisms in both SLC6A4 and the FGA gene significantly affected the symptoms of ASD.

CONCLUSION

Our findings indicate that FGA and SLC6A4 gene interactions may contribute to the phenotypes of ASD rather than the incidence of ASD.

Measles-mumps-rubella vaccination timing and autism among young African American boys: a reanalysis of CDC data

Background

A significant number of children diagnosed with autism spectrum disorder suffer a loss of previously-acquired skills, suggesting neurodegeneration or a type of progressive encephalopathy with an etiological basis occurring after birth. The purpose of this study is to investigate the effectof the age at which children got their first Measles-Mumps-Rubella (MMR) vaccine on autism incidence. This is a reanalysis of the data set, obtained from the U.S. Centers for Disease Control and Protection (CDC), used for the Destefano et al. 2004 publication on the timing of the first MMR vaccine and autism diagnoses.

Methods

The author embarked on the present study to evaluate whether a relationship exists between child age when the first MMR vaccine was administered among cases diagnosed with autism and controls born between 1986 through 1993 among school children in metropolitan Atlanta. The Pearson’s chi-squared method was used to assess relative risks of receiving an autism diagnosis within the total cohort as well as among different race and gender categories.

Results

When comparing cases and controls receiving their first MMR vaccine before and after 36 months of age, there was a statistically significant increase in autism cases specifically among African American males who received the first MMR prior to 36 months of age. Relative risks for males in general and African American males were 1.69 (p=0.0138) and 3.36 (p=0.0019), respectively. Additionally, African American males showed an odds ratio of 1.73 (p=0.0200) for autism cases in children receiving their first MMR vaccine prior to 24 months of age versus 24 months of age and thereafter.

Conclusions

The present study provides new epidemiologic evidence showing that African American males receiving the MMR vaccine prior to 24 months of age or 36 months of age are more likely to receive an autism diagnosis.

Response inhibition and serotonin in autism: a functional MRI study using acute tryptophan depletion

Stereotyped, repetitive behaviours in autism may reflect deficits in serotonin-modulated inhibitory control. Daly et al. use fMRI to compare the effects of acute tryptophan depletion in adult males with autism and controls performing the Go/No-Go task. Opposite effects are seen in the two groups, consistent with altered inhibition in autism.

It has been suggested that the restricted, stereotyped and repetitive behaviours typically found in autism are underpinned by deficits of inhibitory control. The biological basis of this is unknown but may include differences in the modulatory role of neurotransmitters, such as serotonin, which are implicated in the condition. However, this has never been tested directly. We therefore assessed the modifying role of serotonin on inhibitory brain function during a Go/No-Go task in 14 adults with autism and normal intelligence and 14 control subjects that did not differ in gender, age and intelligence. We undertook a double-blind, placebo-controlled, crossover trial of acute tryptophan depletion using functional magnetic resonance imaging. Following sham, adults with autism relative to controls had reduced activation in key inhibitory regions of inferior frontal cortex and thalamus, but increased activation of caudate and cerebellum. However, brain activation was modulated in opposite ways by depletion in each group. Within autistic individuals depletion upregulated fronto-thalamic activations and downregulated striato-cerebellar activations toward control sham levels, completely ‘normalizing’ the fronto-cerebellar dysfunctions. The opposite pattern occurred in controls. Moreover, the severity of autism was related to the degree of differential modulation by depletion within frontal, striatal and thalamic regions. Our findings demonstrate that individuals with autism have abnormal inhibitory networks, and that serotonin has a differential, opposite, effect on them in adults with and without autism. Together these factors may partially explain the severity of autistic behaviours and/or provide a novel (tractable) treatment target.

Switching brain serotonin with oxytocin

Serotonin (5-HT) and oxytocin (OXT) are two neuromodulators involved in human affect and sociality and in disorders like depression and autism. We asked whether these chemical messengers interact in the regulation of emotion-based behavior by administering OXT or placebo to 24 healthy subjects and mapping cerebral 5-HT system by using 2'-methoxyphenyl-(N-2'-pyridinyl)-p-[(18)F]fluoro-benzamidoethylpiperazine ([(18)F]MPPF), an antagonist of 5-HT1A receptors. OXT increased [(18)F]MPPF nondisplaceable binding potential (BPND) in the dorsal raphe nucleus (DRN), the core area of 5-HT synthesis, and in the amygdala/hippocampal complex, insula, and orbitofrontal cortex. Importantly, the amygdala appears central in the regulation of 5-HT by OXT: [(18)F]MPPF BPND changes in the DRN correlated with changes in right amygdala, which were in turn correlated with changes in hippocampus, insula, subgenual, and orbitofrontal cortex, a circuit implicated in the control of stress, mood, and social behaviors. OXT administration is known to inhibit amygdala activity and results in a decrease of anxiety, whereas high amygdala activity and 5-HT dysregulation have been associated with increased anxiety. The present study reveals a previously unidentified form of interaction between these two systems in the human brain, i.e., the role of OXT in the inhibitory regulation of 5-HT signaling, which could lead to novel therapeutic strategies for mental disorders.

The developmental disruptions of serotonin signaling may involved in autism during early brain development

Autism is a developmental disorder defined by the presence of a triad of communication, social and stereo typical behavioral characteristics with onset before 3years of age. In spite of the fact that there are potential environmental factors for autistic behavior, the dysfunction of serotonin during early development of the brain could be playing a role in this prevalence rise. Serotonin can modulate a number of developmental events, including cell division, neuronal migration, cell differentiation and synaptogenesis. Hyperserotonemia during fetal development results in the loss of serotonin terminals through negative feedback. The increased serotonin causes a decrease of oxytocin in the paraventricular nucleus of the hypothalamus and an increase in calcitonin gene-related peptide (CGRP) in the central nucleus of the amygdale, which are associated with social interactions and vital in autism. However, hyposerotonemia may be also relevant to the development of sensory as well as motor and cognitive faculties. And the paucity of placenta-derived serotonin should have potential importance when the pathogenesis of autism is considered. This review briefly summarized the developmental disruptions of serotonin signaling involved in the pathogenesis of autism during early development of the brain.

Prenatal exposure to antidepressants and language competence at age three: results from a large population-based pregnancy cohort in Norway

OBJECTIVE

To examine the association between maternal use of selective serotonin reuptake inhibitors (SSRI) in pregnancy and language competence in their children at age three taking into account maternal symptoms of anxiety and depression.

DESIGN

Population-based prospective pregnancy cohort study.

SETTING

The Norwegian Mother and Child Cohort Study; recruited pregnant women from 1999 through 2008.

POPULATION

45,266 women with 51,748 singleton pregnancies.

METHODS

The association between short- or long-term use of SSRI during pregnancy and language competence in the child was investigated using multinomial logistic regression with three outcome categories: long, complicated sentences, fairly complete sentences and language delay.

MAIN OUTCOME MEASURES

Children's language competence at age three measured by maternal report on a validated language grammar scale.

RESULTS

Women reported use of SSRI in 386 (0.7%) pregnancies. Of these, 161 (42%) reported long-term use. Compared with children whose mothers took no SSRI, using the best language category as the reference, adjusted relative risk ratios (RRR) of having fairly complete sentences were 1.21 (95% CI 0.85-1.72) and 2.28 (1.54-3.38) for short- and long-term SSRI use, respectively. The adjusted RRRs of language delay were 0.86 (0.42-1.76) and 2.30 (1.21-4.37). Symptoms of anxiety and depression in pregnancy were independently related to language delay, adjusted RRR 1.25 (1.03-1.50) and 1.83 (1.40-2.40) for short- and long-term symptoms, respectively.

CONCLUSIONS

Prolonged use of SSRI during pregnancy was associated with lower language competence in children by age three independently of depression. Having symptoms of depression throughout pregnancy had an independent effect.

Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism

Serotonin and vitamin D have been proposed to play a role in autism; however, no causal mechanism has been established. Here, we present evidence that vitamin D hormone (calcitriol) activates the transcription of the serotonin-synthesizing gene tryptophan hydroxylase 2 (TPH2) in the brain at a vitamin D response element (VDRE) and represses the transcription of TPH1 in tissues outside the blood-brain barrier at a distinct VDRE. The proposed mechanism explains 4 major characteristics associated with autism: the low concentrations of serotonin in the brain and its elevated concentrations in tissues outside the blood-brain barrier; the low concentrations of the vitamin D hormone precursor 25-hydroxyvitamin D [25(OH)D3]; the high male prevalence of autism; and the presence of maternal antibodies against fetal brain tissue. Two peptide hormones, oxytocin and vasopressin, are also associated with autism and genes encoding the oxytocin-neurophysin I preproprotein, the oxytocin receptor, and the arginine vasopressin receptor contain VDREs for activation. Supplementation with vitamin D and tryptophan is a practical and affordable solution to help prevent autism and possibly ameliorate some symptoms of the disorder.

A review of the serotonin transporter and prenatal cortisol in the development of autism spectrum disorders

The diagnosis of autism spectrum disorder (ASD) during early childhood has a profound effect not only on young children but on their families. Aside from the physical and behavioural issues that need to be dealt with, there are significant emotional and financial costs associated with living with someone diagnosed with ASD. Understanding how autism occurs will assist in preparing families to deal with ASD, if not preventing or lessening its occurrence.

Serotonin plays a vital role in the development of the brain during the prenatal and postnatal periods, yet very little is known about the serotonergic systems that affect children with ASD. This review seeks to provide an understanding of the biochemistry and physiological actions of serotonin and its termination of action through the serotonin reuptake transporter (SERT). Epidemiological studies investigating prenatal conditions that can increase the risk of ASD describe a number of factors which elevate plasma cortisol levels causing such symptoms during pregnancy such as hypertension, gestational diabetes and depression. Because cortisol plays an important role in driving dysregulation of serotonergic signalling through elevating SERT production in the developing brain, it is also necessary to investigate the physiological functions of cortisol, its action during gestation and metabolic syndromes.

Autism spectrum disorders: the quest for genetic syndromes

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disabilities with various etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of ASD remains unclear. A number of genetic syndromes manifest ASD at higher than expected frequencies compared to the general population. These syndromes account for more than 10% of all ASD cases and include tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Williams, Duchenne, etc. Clinicians are increasingly required to recognize genetic disorders in individuals with ASD, in terms of providing proper care and prognosis to the patient, as well as genetic counseling to the family. Vice versa, it is equally essential to identify ASD in patients with genetic syndromes, in order to ensure correct management and appropriate educational placement. During investigation of genetic syndromes, a number of issues emerge: impact of intellectual disability in ASD diagnoses, identification of autistic subphenotypes and differences from idiopathic autism, validity of assessment tools designed for idiopathic autism, possible mechanisms for the association with ASD, etc. Findings from the study of genetic syndromes are incorporated into the ongoing research on autism etiology and pathogenesis; different syndromes converge upon common biological backgrounds (such as disrupted molecular pathways and brain circuitries), which probably account for their comorbidity with autism. This review paper critically examines the prevalence and characteristics of the main genetic syndromes, as well as the possible mechanisms for their association with ASD.

Parental depression, maternal antidepressant use during pregnancy, and risk of autism spectrum disorders: population based case-control study

OBJECTIVE

To study the association between parental depression and maternal antidepressant use during pregnancy with autism spectrum disorders in offspring.

DESIGN

Population based nested case-control study.

SETTING

Stockholm County, Sweden, 2001-07.

PARTICIPANTS

4429 cases of autism spectrum disorder (1828 with and 2601 without intellectual disability) and 43,277 age and sex matched controls in the full sample (1679 cases of autism spectrum disorder and 16,845 controls with data on maternal antidepressant use nested within a cohort (n=589,114) of young people aged 0-17 years.

MAIN OUTCOME MEASURE

A diagnosis of autism spectrum disorder, with or without intellectual disability.

EXPOSURES

Parental depression and other characteristics prospectively recorded in administrative registers before the birth of the child. Maternal antidepressant use, recorded at the first antenatal interview, was available for children born from 1995 onwards.

RESULTS

A history of maternal (adjusted odds ratio 1.49, 95% confidence interval 1.08 to 2.08) but not paternal depression was associated with an increased risk of autism spectrum disorders in offspring. In the subsample with available data on drugs, this association was confined to women reporting antidepressant use during pregnancy (3.34, 1.50 to 7.47, P=0.003), irrespective of whether selective serotonin reuptake inhibitors (SSRIs) or non-selective monoamine reuptake inhibitors were reported. All associations were higher in cases of autism without intellectual disability, there being no evidence of an increased risk of autism with intellectual disability. Assuming an unconfounded, causal association, antidepressant use during pregnancy explained 0.6% of the cases of autism spectrum disorder.

CONCLUSIONS

In utero exposure to both SSRIs and non-selective monoamine reuptake inhibitors (tricyclic antidepressants) was associated with an increased risk of autism spectrum disorders, particularly without intellectual disability. Whether this association is causal or reflects the risk of autism with severe depression during pregnancy requires further research. However, assuming causality, antidepressant use during pregnancy is unlikely to have contributed significantly towards the dramatic increase in observed prevalence of autism spectrum disorders as it explained less than 1% of cases.

Placenta-derived hypo-serotonin situations in the developing forebrain cause autism

Autism is a pervasive developmental disorder that is characterized by the behavioral traits of impaired social cognition and communication, and repetitive and/or obsessive behavior and interests. Although there are many theories and speculations about the pathogenetic causes of autism, the disruption of the serotonergic system is one of the most consistent and well-replicated findings. Recently, it has been reported that placenta-derived serotonin is the main source in embryonic day (E) 10-15 mouse forebrain, after that period, the serotonergic fibers start to supply serotonin into the forebrain. E 10-15 is the very important developing period, when cortical neurogenesis, migration and initial axon targeting are processed. Since all these events have been considered to be involved in the pathogenesis of autism and they are highly controlled by serotonin signals, the paucity of placenta-derived serotonin should have potential importance when the pathogenesis of autism is considered. I, thus, postulate a hypothesis that placenta-derived hypo-serotonin situations in the developing forebrain cause autism. The hypothesis is as follows. Various factors, such as inflammation, dysfunction of the placenta, together with genetic predispositions cause a decrease of placenta-derived serotonin levels. The decrease of placenta-derived serotonin levels leads to hypo-serotonergic situations in the forebrain of the fetus. The paucity of serotonin in the forebrain leads to mis-wiring in important regions which are responsible for the theory of mind. The paucity of serotonin in the forebrain also causes over-growth of serotonergic fibers. These disturbances result in network deficiency and aberration of the serotonergic system, leading to the autistic phenotypes.