Risperidone and the 5-HT2A receptor antagonist M100907 improve probabilistic reversal learning in BTBR T + tf/J mice

Poly (I:C)-induced maternal immune activation generates impairment of reversal learning performance in offspring

Maternal immune activation (MIA) induces a variety of behavioral and brain abnormalities in offspring of rodent models, compatible with neurodevelopmental disorders, such as schizophrenia or autism. However, it remains controversial whether MIA impairs reversal learning, a basic expression of cognitive flexibility that seems to be altered in schizophrenia. In the present study, MIA was induced by administration of a single dose of polyriboinosinic-polyribocytidylic acid (Poly (I:C) (5 mg/kg i.p.)) or saline to mouse pregnant dams in gestational day (GD) 9.5. Immune activation was monitored through changes in weight and temperature. The offspring were evaluated when they reached adulthood (8 weeks) using a touchscreen-based system to investigate the effects of Poly (I:C) on discrimination and reversal learning performance. After an initial pre-training, mice were trained to discriminate between two different stimuli, of which only one was rewarded (acquisition phase). When the correct response reached above 80% values for two consecutive days, the images were reversed (reversal phase) to assess the adaptation capacity to a changing environment. Maternal Poly (I:C) treatment did not interfere with the learning process but induced deficits in reversal learning compared to control saline animals. Thus, the accuracy in the reversal phase was lower, and Poly (I:C) animals required more sessions to complete it, suggesting impairments in cognitive flexibility. This study advances the knowledge of how MIA affects behavior, especially cognitive domains that are impaired in schizophrenia. The findings support the validity of the Poly (I:C)-based MIA model as a tool to develop pharmacological treatments targeting cognitive deficits associated with neurodevelopmental disorders.

Transcriptome analysis to explore the mechanism of downregulated TNIK influencing the effect of risperidone

Background

Risperidone is one of the most reliable and effective antipsychotics for schizophrenia treatment. However, the mechanism of action of risperidone is not yet fully understood. Traf2 and Nck-interacting protein kinase (TNIK), a schizophrenia susceptibility gene, is associated with risperidone treatment response. Our previous in vitro experiments confirmed that downregulated TNIK affected the effect of risperidone on downstream targets. However, the effect of downregulated TNIK on risperidone-induced molecular expression remains to be further explored.

Methods

Transcriptome analysis was performed on U251 cells subjected to risperidone, TNIK siRNA, and no treatment, respectively. Compared to the no-treatment group, two groups of DEGs were screened out and then intersected with the schizophrenia-related genes to screen the cross-talk genes. Those DEGs were analyzed using GO and KEGG. STRING and Cytoscape were used to construct a protein-protein interaction (PPI) network for the cross-talk gene.

Results

The results showed that the parathyroid hormone synthesis, secretion, and action were significantly enriched after risperidone treatment. Downregulated TNIK could have an impact on the collagen-containing extracellular matrix, signaling receptor activator activity, and PI3K-Akt signaling pathway. Interestingly, bone mineralization function and calcium signaling pathway were enriched in the cross-talk genes. Additionally, FGFR2, FGF1, and FGFR might be the potential targets for TNIK affecting the effects of risperidone.

Conclusion

The study indicated that risperidone primarily influences functions and/or pathways associated with bone metabolism, potentially contributing to the adverse effect of osteoporosis. Our study may offer a novel perspective on investigating the mechanisms underlying the adverse effects of risperidone.

Synthesis, molecular docking, ADMET, and evaluation of the anxiolytic effect in adult zebrafish of synthetic chalcone (E)-3-(4-(dimethylamino)phenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one: An in vivo and in silico approach

BACKGROUND

Anxiety disorders represent the complex interaction between biological, psychological, temperamental, and environmental factors; drugs available to treat anxiety such as benzodiazepines (BZDs) are associated with several unwanted side effects. Although there are useful treatments, there is still a need for more effective anxiolytics with better safety profiles than BZDs. Chalcones or 1,3-diphenyl-2-proper-1-ones can be an alternative since this class of compounds has shown therapeutic potential mainly due to interactions with GABAA receptors and serotonergic system.

OBJECTIVES

This study evaluated the anxiolytic potential of chalcone (E)-3-(4-(dimethylamino)phenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (C2OHPDA) in adult zebrafish (Danio rerio) (ZFa).

METHODS

Each animal (n = 6/group) was treated intraperitoneally (i.p.; 20 μL) with the chalcone (4, 20, and 40 mg/kg) and with the vehicle (DMSO 3%; 20 μL), being submitted to the tests of locomotor activity and 96-h acute toxicity. The light/dark test was also performed, and the serotonergic mechanism (5-HT) was evaluated through the antagonists of the 5-HTR1 , 5-HTR2A/2C , and 5-HTR3A/3B receptors. It was investigated the prediction of the chalcone's position and preferential orientation concerning its receptor, as well as the pharmacokinetic parameters (ADMET) involved in the process after administration.

RESULTS

As a result, C2OHPDA was not toxic and reduced the locomotor activity of ZFa. Furthermore, chalcone demonstrated an anxiolytic effect on the central nervous system (CNS), mediated by the serotonergic system, with action on 5-HT2A and 5-HTR3A/3B receptors. The interaction of C2OHPDA with 5-HT2A R and 5-HT3A receptors was confirmed by molecular docking study, the affinity energy observed was -8.7 and -9.1 kcal/mol, respectively.

CONCLUSION

Thus, this study adds new evidence and highlights that chalcone can potentially be used to develop compounds with anxiolytic properties.

Serotonergic neurotransmission mediated cognitive dysfunction in two mouse models of sepsis-associated encephalopathy

BACKGROUND

Patients with sepsis-associated encephalopathy (SAE) often exhibit cognitive impairments. Despite this, the underlying mechanisms of SAE remain largely unexplored. Here, we explored the role of serotonergic neurotransmission in cognitive dysfunction of two mouse models of SAE.

METHODS

The mouse models of SAE were established by injection of lipopolysaccharide (LPS, 10 mg/kg, intraperitoneal) and cecal ligation puncture (CLP) respectively. Barnes maze, new object recognition test and open field test were used to evaluate the effects of fluoxetine (selective serotonin reuptake inhibitor) and cyproheptadine (nonselective 5-HT2 receptor antagonist) on cognition and motor activity of mice. Additionally, WAY100635 (5-HT1A receptor antagonist) was co-administered with fluoxetine to explore the mechanism underlying effect of fluoxetine on cognitive impairments of SAE. Enzyme-linked immunosorbent assay (ELISA) was performed to determine 5-HT levels in hippocampus, brainstem and frontal lobe of experimental groups.

RESULTS

Both LPS-induced sepsis and CLP induced sepsis resulted in a notable learning deficit. Fluoxetine ameliorated, while cyproheptadine aggravated, cognitive impairment in two classic mouse models of SAE. The cognition-enhancing effect of fluoxetine is reversed by WAY100635. Decreased 5-HT levels in hippocampus, brainstem and frontal lobe were observed in LPS septic model and CLP septic model. Notably, both fluoxetine and cyproheptadine significantly increased 5-HT levels in those brain regions in LPS septic model. Additionally, fluoxetine significantly increased 5-HT levels in frontal lobe of CLP septic model.

CONCLUSIONS

Our study demonstrated that serotonergic neurotransmission plays a significant role in mechanisms underlying cognitive impairment in SAE. These findings contribute to identification of novel targets to prevent and arrest cognitive impairment in SAE.

The brain serotonin system in autism

Autism spectrum disorders (ASDs) are among the most common neurodevelopmental diseases. These disorders are characterized by lack of social interaction, by repetitive behavior, and often anxiety and learning disabilities. The brain serotonin (5-HT) system is known to be crucially implicated in a wide range of physiological functions and in the control of different kinds of normal and pathological behavior. A growing number of studies indicate the involvement of the brain 5-HT system in the mechanisms underlying both ASD development and ASD-related behavioral disorders. There are some review papers describing the role of separate key players of the 5-HT system in an ASD and/or autistic-like behavior. In this review, we summarize existing data on the participation of all members of the brain 5-HT system, namely, 5-HT transporter, tryptophan hydroxylase 2, MAOA, and 5-HT receptors, in autism in human and various animal models. Additionally, we describe the most recent studies involving modern techniques for in vivo regulation of gene expression that are aimed at identifying exact roles of 5-HT receptors, MAOA, and 5-HT transporter in the mechanisms underlying autistic-like behavior. Altogether, results of multiple research articles show that the brain 5-HT system intimately partakes in the control of some types of ASD-related behavior, and that specific changes in a function of a certain 5-HT receptor, transporter, and/or enzyme may normalize this aberrant behavior. These data give hope that some of clinically used 5-HT-related drugs have potential for ASD treatment.

Effect of lysergic acid diethylamide (LSD) on reinforcement learning in humans

BACKGROUND

The non-selective serotonin 2A (5-HT2A) receptor agonist lysergic acid diethylamide (LSD) holds promise as a treatment for some psychiatric disorders. Psychedelic drugs such as LSD have been suggested to have therapeutic actions through their effects on learning. The behavioural effects of LSD in humans, however, remain incompletely understood. Here we examined how LSD affects probabilistic reversal learning (PRL) in healthy humans.

METHODS

Healthy volunteers received intravenous LSD (75 μg in 10 mL saline) or placebo (10 mL saline) in a within-subjects design and completed a PRL task. Participants had to learn through trial and error which of three stimuli was rewarded most of the time, and these contingencies switched in a reversal phase. Computational models of reinforcement learning (RL) were fitted to the behavioural data to assess how LSD affected the updating ('learning rates') and deployment of value representations ('reinforcement sensitivity') during choice, as well as 'stimulus stickiness' (choice repetition irrespective of reinforcement history).

RESULTS

Raw data measures assessing sensitivity to immediate feedback ('win-stay' and 'lose-shift' probabilities) were unaffected, whereas LSD increased the impact of the strength of initial learning on perseveration. Computational modelling revealed that the most pronounced effect of LSD was the enhancement of the reward learning rate. The punishment learning rate was also elevated. Stimulus stickiness was decreased by LSD, reflecting heightened exploration. Reinforcement sensitivity differed by phase.

CONCLUSIONS

Increased RL rates suggest LSD induced a state of heightened plasticity. These results indicate a potential mechanism through which revision of maladaptive associations could occur in the clinical application of LSD.

Acute psilocybin enhances cognitive flexibility in rats

Psilocybin has been shown to improve symptoms of depression and anxiety when combined with psychotherapy or other clinician-guided interventions. To understand the neural basis for this pattern of clinical efficacy, experimental and conceptual approaches that are different than traditional laboratory models of anxiety and depression are needed. A potential novel mechanism is that acute psilocybin improves cognitive flexibility, which then enhances the impact of clinician-assisted interventions. Consistent with this idea, we find that acute psilocybin robustly improves cognitive flexibility in male and female rats using a task where animals switched between previously learned strategies in response to uncued changes in the environment. Psilocybin did not influence Pavlovian reversal learning, suggesting that its cognitive effects are selective to enhanced switching between previously learned behavioral strategies. The serotonin (5HT) 2 A receptor antagonist ketanserin blocked psilocybin's effect on set-shifting, while a 5HT2C-selective antagonist did not. Ketanserin alone also improved set-shifting performance, suggesting a complex relationship between psilocybin's pharmacology and its impact on flexibility. Further, the psychedelic drug 2,5-Dimethoxy-4-iodoamphetamine (DOI) impaired cognitive flexibility in the same task, suggesting that this effect of psilocybin does not generalize to all other serotonergic psychedelics. We conclude that the acute impact of psilocybin on cognitive flexibility provides a useful behavioral model to investigate its neuronal effects relevant to its positive clinical outcome.

The comparative effectiveness of metformin and risperidone in a rat model of valproic acid-induced autism, Potential role for enhanced autophagy

RATIONALE

Risperidone is the first antipsychotic to be approved by Food and Drug Administration (FDA) for treating autism spectrum disorder (ASD). The potential efficacy of metformin in preventing and/or controlling ASD behavioral deficits was also recently reported. Suppression of hippocampus autophagy was suggested as a potential pathologic mechanism in ASD.

OBJECTIVES

Is metformin's ability to improve ASD clinical phenotype driven by its autophagy-enhancing properties? And does hippocampus autophagy enhancement underlie risperidone's efficacy as well? Both questions are yet to be answered.

METHODS

The effectiveness of metformin on alleviation of ASD-like behavioral deficits in adolescent rats exposed prenatally to valproic acid (VPA) was compared to that of risperidone. The potential modulatory effects of risperidone on hippocampal autophagic activity were also assessed and compared to those of metformin.

RESULTS

Male offspring exposed to VPA during gestation exhibited marked anxiety, social impairment and aggravation of stereotyped grooming; such deficits were efficiently rescued by postnatal risperidone or metformin therapy. This autistic phenotype was associated with suppressed hippocampal autophagy; as evidenced by reduced gene/dendritic protein expression of LC3B (microtubule-associated proteins 1 light chain 3B) and increased somatic P62 (Sequestosome 1) protein aggregates. Interestingly, compared to risperidone, the effectiveness of metformin in controlling ASD symptoms and improving hippocampal neuronal survival was well correlated to its ability to markedly induce pyramidal neuronal LC3B expression while lowering P62 accumulation.

CONCLUSIONS

Our work highlights, for the first time, positive modulation of hippocampus autophagy as potential mechanism underlying improvements in autistic behaviors, observed with metformin, as well as risperidone, therapy.

Trait sensitivity to negative feedback in rats is associated with increased expression of serotonin 5-HT2A receptors in the ventral hippocampus

One of the most important yet still underappreciated mechanisms of depression is distorted cognition, with aberrant sensitivity to negative feedback being one of the best-described examples. As serotonin has been identified as an important modulator of sensitivity to feedback and because the hippocampus has been implicated in the mediation of learning from positive and negative outcomes, the present study aimed to identify differences in the expression of various genes encoding 5-HT receptors in this brain region between the rats displaying trait sensitivity and insensitivity to negative feedback. The results demonstrated that trait sensitivity to negative feedback is associated with increased mRNA expression of the 5-HT2A receptors in the rat ventral hippocampus (vHipp). Further analysis revealed that this increased expression might be modulated epigenetically by miRNAs with a high target score for the Htr2a gene (miR-16-5p and miR-15b-5p). Additionally, although not confirmed at the protein level, trait sensitivity to negative feedback was associated with decreased expression of mRNA encoding the 5-HT7 receptor in the dorsal hippocampus (dHipp). We observed no statistically significant intertrait differences in the expression of the Htr1a, Htr2c, and Htr7 genes in the vHipp and no statistically significant intertrait differences in the expression of the Htr1a, Htr2a, and Htr2c genes in the dHipp of the tested animals. These results suggest that resilience to depression manifested by reduced sensitivity to negative feedback may be mediated via these receptors.

Impairments in operant probabilistic reversal learning in BTBR T+tf/J male and female mice

Autism spectrum disorder (ASD) presents with two core symptoms, impairments in social communication and the presence of restricted, repetitive behaviors (RRBs). RRBs are commonly linked to a lack of behavioral flexibility, having a significant negative impact on daily functioning for ASD individuals and their caregivers. Commonly utilized tests of behavioral flexibility employ a traditional deterministic reward approach where choices are either correct or incorrect throughout testing. The incorporation of an 80 %/20 % probabilistic reversal learning paradigm allows for the examination of flexible behavior in the face of variable outcomes, a more ecologically relevant approach. In this task, one specific choice is reinforced on 80 % of trials and the opposite or incorrect choice is reinforced on 20% of trials. Upon successful discrimination learning, the reward contingencies are switched so that the correct choice is now reinforced 20% of trials and the incorrect choice reinforced 80 % of trials, making it the new optimal choice. This translational task has been previously validated in ASD individuals and animal models of ASD, including the BTBR T + tf/J strain. Our lab and others have demonstrated that male BTBR T + tf/J mice have higher expression of lower order RRBs and display deficits in spatial probabilistic reversal learning tasks using a T-maze apparatus. Instead, female BTBR mice do not express the same lower order RRBs and results are mixed on whether females demonstrate similar probabilistic reversal learning deficits in a T-maze. Therefore, the purpose of this study was to assess the validity of using operant chambers to examine BTBR mouse performance on an 80 %/20 % probabilistic reversal learning task and to also examine the sex-specific differences in reversal learning performance in both mouse strains. Results show that BTBR mice, irrespective of sex, were impaired on the reversal learning, requiring more days and trials to reach reversal criterion compared to C57BL/6J mice. These results parallel previous strain findings in the spatial dependent T-maze task in male mice. Further error analysis showed that the impaired behavioral flexibility was due to elevated regressive errors and lose-shift probabilities. BTBR mice have more difficulty maintaining new choice patterns compared to C57BL/6J mice, which supports findings utilizing a spatial T-maze task. Together, these findings further support the use of the BTBR mouse as preclinical models of ASD due to their validity as an ASD model.

A new serotonin 2A receptor antagonist with potential benefits in Non-Alcoholic Fatty Liver Disease

Peripheral 5-hydroxytryptamine 2A receptor (5-HT2AR) could be a new pharmacological target for NASH, an evolution of NAFLD characterized by hepatic steatosis, cytoskeletal alterations, and hepatic inflammation that can arise with or without fibrosis. SJT4a is a synthetic β-carboline antagonist for 5-HT2AR developed by SJT molecular research to treat NASH. We performed a combined in silico/in vivo study on this potential drug to elucidate its activity and possible mechanism of action. The in silico protocol compares SJT4a with four known 5-HT2AR ligands with different activities (LSD, methiothepin, zotepine, risperidone). We performed molecular docking calculations, evaluation of binding energy by AI-based methods and Molecular Dynamics simulations of the five ligand-target complexes. Moreover, we used a pseudo-semantic analysis to evaluate the potential mechanism of action of SJT4a. In silico predictions and pseudo-semantic analysis suggested antagonistic activity for SJT4a. The in silico prediction was confirmed by [³H]-5HT radioligand binding together with SJT4a competition analysis in CHO-K1 cell cultures expressing 5-HT2AR. SJT4a was then tested in vivo. We investigated the effect of 8 weeks of treatment with SJT4A on metabolic parameters, liver pathology, NAFLD activity score, and fibrosis stage in male DIO-NASH C57BL/6 J mice diet-induced obesity fed with an obesogenic diet compared with DIO-NASH and LEAN-CHOW vehicles. In our tests, SJT4a showed intense activity in diminishing the most relevant hallmarks of NASH in the DIO-NASH mice model. We proposed a possible mode of action for SJT4a based on its 5-HT2AR antagonist activity.

Acute psilocybin enhances cognitive flexibility in rats

Psilocybin has been shown to improve symptoms of depression and anxiety when combined with psychotherapy or other clinician-guided interventions. To understand the neural basis for this pattern of clinical efficacy, experimental and conceptual approaches that are different than traditional laboratory models of anxiety and depression are needed. A potential novel mechanism is that acute psilocybin improves cognitive flexibility, which then enhances the impact of clinician-assisted interventions. Consistent with this idea, we find that acute psilocybin robustly improves cognitive flexibility in male and female rats using a task where animals switched between previously learned strategies in response to uncued changes in the environment. Psilocybin did not influence Pavlovian reversal learning, suggesting that its cognitive effects are selective to enhanced switching between previously learned behavioral strategies. The serotonin (5HT) 2A receptor antagonist ketanserin blocked psilocybin's effect on set-shifting, while a 5HT2C-selective antagonist did not. Ketanserin alone also improved set-shifting performance, suggesting a complex relationship between psilocybin's pharmacology and its impact on flexibility. Further, the psychedelic drug 2,5-Dimethoxy-4-iodoamphetamine (DOI) impaired cognitive flexibility in the same task, suggesting that this effect of psilocybin does not generalize to all other serotonergic psychedelics. We conclude that the acute impact of psilocybin on cognitive flexibility provides a useful behavioral model to investigate its neuronal effects relevant to its positive clinical outcome.

Lopez S, Amodeo DA. Impact of specific serotonin receptor modulation on restricted repetitive behaviors

Restricted, repetitive behaviors (RRBs) are commonly divided into two behavioral categories, lower-order and higher-order RRBs. Individuals displaying lower-order motoric RRBs may express repetitive hand flapping behaviors, body rocking back and forth movements, and continuous body spinning. Higher-order RRBs most commonly cover the behavior inflexibility and cognitive rigidity commonly found in disorders such as autism spectrum disorder and obsessive-compulsive disorder. Various neuropsychiatric disorders are plagued by RRBs yet no FDA-approved treatments have been identified. In rodents, lower-order RRBs are commonly measured through various tasks, such as repetitive self-grooming, marble burying, and stereotypic motor behaviors. This review focuses on the effects that modulation of specific serotonin receptors have on lower-order RRBs. Although there is research examining how changes in 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT6, and 5-HT7 receptor modulation, more research has focused on the 5-HT1A, 5-HT2A, and 5-HT2C receptors. The accumulating data suggest that increasing 5-HT1A activation decreases RRBs while blocking 5-HT1A activation has no effect on RRBs. While there are mixed findings regarding the impact of 5-HT2A modulation on RRBs, the general trend shows mixed effects of 5-HT2A receptor activation RRB expression, whereas blockade generally decreases RRBs. 5-HT2C receptor activation can modulate RRBs in either direction depending on the 5-HT2C drug used, blocking 5-HT2C activation only seems to show therapeutic properties when 5-HT2C activation is already elevated. The other 5-HT receptors have been explored far less but show promise as potential targets for regulating RRBs. Although it is less clear due to the involvement of 5-HT1D, 5-HT1A activation increases RRBs, and blocking 5-HT1A tends to decrease RRBs. 5-HT2B activation could reduce RRBs, while inhibiting 5-HT2B does not impact RRBs. Increasing 5-HT3 has not been shown to affect RRBs. Yet, increases in RRBs have been observed in Htr3a KO mice. 5-HT6 receptor activation can increase RRBs, while blocking 5-HT6 activity tends to decrease RRBs. Lastly, neither increasing or blocking 5-HT7 activity can reduce RRBs. In sum, there is no uniform pattern in whether all specific 5-HT receptors affect RRBs in either direction, instead, there is evidence suggesting that different 5-HT receptors can modulate RRBs in different directions. Further researching the less explored receptors and aiming to understand why these receptors can differently modulate RRBs, may play a key role in developing therapeutics that treat RRBs.

Cognitive impairment in psychiatric diseases: Biomarkers of diagnosis, treatment, and prevention

Psychiatric diseases, such as schizophrenia, bipolar disorder, autism spectrum disorder, and major depressive disorder, place a huge health burden on society. Cognitive impairment is one of the core characteristics of psychiatric disorders and a vital determinant of social function and disease recurrence in patients. This review thus aims to explore the underlying molecular mechanisms of cognitive impairment in major psychiatric disorders and identify valuable biomarkers for diagnosis, treatment and prevention of patients.

Perineuronal Nets in the Dorsomedial Striatum Contribute to Behavioral Dysfunction in Mouse Models of Excessive Repetitive Behavior

Background

Excessive repetitive behavior is a debilitating symptom of several neuropsychiatric disorders. Parvalbumin-positive inhibitory interneurons in the dorsal striatum have been linked to repetitive behavior, and a sizable portion of these cells are surrounded by perineuronal nets (PNNs), specialized extracellular matrix structures. Although PNNs have been associated with plasticity and neuropsychiatric disease, no previous studies have investigated their involvement in excessive repetitive behavior.

Methods

We used histochemistry and confocal imaging to investigate PNNs surrounding parvalbumin-positive cells in the dorsal striatum of 4 mouse models of excessive repetitive behavior (BTBR, Cntnap2, Shank3, prenatal valproate treatment). We then investigated one of these models, the BTBR mouse, in detail, with DiI labeling, in vivo and in vitro recordings, and behavioral analyses. We next degraded PNNs in the dorsomedial striatum (DMS) using the enzyme chondroitinase ABC and assessed dendritic spine density, electrophysiology, and repetitive behavior.

Results

We found a greater percentage of parvalbumin-positive interneurons with PNNs in the DMS of all 4 mouse models of excessive repetitive behavior compared with control mice. In BTBR mice, we found fewer dendritic spines on medium spiny neurons (targets of parvalbumin-positive interneurons) and differences in neuronal oscillations as well as inhibitory postsynaptic potentials compared with control mice. Reduction of DMS PNNs in BTBR mice altered dendritic spine density and inhibitory responses and normalized repetitive behavior.

Conclusions

These findings suggest that cellular abnormalities in the DMS are associated with maladaptive repetitive behaviors and that manipulating PNNs can restore normal levels of repetitive behavior while altering DMS dendritic spines and inhibitory signaling.

Brief Report: Feasibility of the Probabilistic Reversal Learning Task as an Outcome Measure in an Intervention Trial for Individuals with Autism Spectrum Disorder

Cognitive flexibility deficits are a hallmark feature of autism spectrum disorder (ASD), but few evidence-based behavioral interventions have successfully addressed this treatment target. Outcome measurement selection may help account for previous findings. The probabilistic reversal learning task (PRL) is a measure of cognitive flexibility previously validated for use in ASD, but its use as an outcome measure has not yet been assessed. The current study examined the feasibility, reproducibility, and sensitivity of PRL in a within-subjects trial of Regulating Together, a group-based intervention targeting emotion regulation. We demonstrated the PRL is highly feasible, showed test-retest reproducibility, and is sensitive to detect change following the intervention. Our findings demonstrate the PRL task may be a useful outcome measure of cognitive flexibility in future intervention trials in ASD.

Serotonin Receptors as Therapeutic Targets for Autism Spectrum Disorder Treatment

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by repetitive and stereotyped behaviors as well as difficulties with social interaction and communication. According to reports for prevalence rates of ASD, approximately 1~2% of children worldwide have been diagnosed with ASD. Although there are a couple of FDA (Food and Drug Administration)—approved drugs for ASD treatment such as aripiprazole and risperidone, they are efficient for alleviating aggression, hyperactivity, and self-injury but not the core symptoms. Serotonin (5-hydroxytryptamine, 5-HT) as a neurotransmitter plays a crucial role in the early neurodevelopmental stage. In particular, 5-HT has been known to regulate a variety of neurobiological processes including neurite outgrowth, dendritic spine morphology, shaping neuronal circuits, synaptic transmission, and synaptic plasticity. Given the roles of serotonergic systems, the 5-HT receptors (5-HTRs) become emerging as potential therapeutic targets in the ASD. In this review, we will focus on the recent development of small molecule modulators of 5-HTRs as therapeutic targets for the ASD treatment.

LSD, afterglow and hangover: Increased episodic memory and verbal fluency, decreased cognitive flexibility

Psychedelics acutely impair cognitive functions, but these impairments decline with growing experiences with psychedelics and microdoses may even exert opposing effects. Given the recent evidence that psychedelics induce neuroplasticity, this explorative study aimed at investigating the potential of psychedelics to sub-acutely change cognition. For this, we applied a randomized, double-blind, placebo-controlled, crossover study with 24 healthy volunteers receiving 50 μg lysergic acid diethylamide (LSD) or an inactive placebo. Sub-acute changes in cognition were measured 24 h after dosing, including memory (Rey-Osterrieth Complex Figure, ROCF; 2D Object-Location Memory Task, OLMT; Rey Auditory-Verbal Learning Test, RAVLT), verbal fluency (phonological; semantic; switch), design fluency (basic; filter; switch), cognitive flexibility (Wisconsin Card Sorting Test, WCST), sustained and switching attention (Trail Making Test, TMT), inhibitory control (Stroop Task) and perceptual reasoning (Block Design Test, BDT). The results show that when compared to placebo and corrected for Body Mass Index (BMI) and abstinence period from psychedelics, LSD sub-acutely improved visuospatial memory (ROCF immediate recall points and percentage, OLMT consolidation percentage) and phonological verbal fluency and impaired cognitive flexibility (WCST: fewer categories achieved; more perseveration, errors and conceptual level responses). In conclusion, the low dose of LSD moderately induced both "afterglow" and "hangover". The improvements in visuospatial memory and phonological fluency suggest that LSD-assisted therapy should be explored as a novel treatment perspective in conditions involving memory and language declines such as brain injury, stroke or dementia.

Sex Differences in Animal Models of Sodium-Valproate-Induced Autism in Postnatal BALB/c Mice: Whole-Brain Histoarchitecture and 5-HT2A Receptor Biomarker Evidence

Simple Summary

Valproic acid (VPA) is a well-known antiepileptic medication and mood stabiliser that is frequently prescribed for the treatment of epilepsy, particularly in children, and has proven human teratogenic activity. VPA inhibits histone deacetylase, which causes teratogenicity and cell toxicity. VPA-induced autism in rodents during the pre- and postnatal periods has shown the development of an autism-like phenotype. In mice, the 14th postnatal day is thought to correspond to the third trimester of human development; it is an important period in which neuronal migration, differentiation, myelination, synaptogenesis and gliogenesis occur in the cerebellum, striatum and hippocampus. Therefore, we exposed postnatal day 14 (PND 14) mice to VPA, which resulted in autistic-like behaviours manifested as reduced social interaction, increased repetitive stereotyped behaviour and anxiety, cognitive dysfunction, lowered sensitivity to pain and neurodevelopmental delay. BALB/c mice were used in this work because they are less reactive to social contact in VPA-induced autism than many other inbred mouse strains, such as C57/129 mice. In humans, two to three times more men are affected by autism spectrum disorder (ASD) than women, and, for this reason, the current study compares the histopathological changes and 5-hydroxy-tryptamine 2A (5-HT2A) receptor protein expression in the brain tissue of male and female animals with VPA-induced autism.

Abstract

Autism spectrum disorder (ASD) is characterised by problems with social interaction, verbal and nonverbal communication and repetitive behaviour. In mice, the 14th postnatal day is believed to correspond to the third trimester of human embryonic development and is considered a vital period for central nervous system development. It has been shown that ASD affects 2 to 3 times more male than female individuals. In the present study, ASD was induced in 14 postnatal day (PND) BALB/c mice using valproic acid (VPA). VPA administration brought about substantial differences in the histoarchitecture of the brain in both male and female mice, linked to behavioural deficits. We observed that both male and female mice showed similar morphological changes in the prefrontal cortex, hippocampus and Purkinje cells. We also observed hair loss from PND 17 to 25, which was again similar between male and female mice. However, there were higher rates of change in the cerebral cortex, frontal cortex and temporal lobe and hippocampus in VPA-treated male animals. With respect to the cerebellum, we did not observe any alterations by haematoxylin and eosin (H&E) staining, but detailed morphological observation using scanning electron microscopy (SEM) showed a higher rate of phenotype changes in VPA-treated male animals. Moreover, 5-HT2A receptor protein levels were upregulated in the cerebral cortex, hippocampus and Purkinje cells in VPA-treated male mice compared with control animals and VPA-treated female mice, as shown by immunohistochemical analysis. Based on all these findings, we conclude that male animals are more susceptible to VPA-induced ASD than females.

Effects of the Partial M1 Muscarinic Cholinergic Receptor Agonist CDD-0102A on Stereotyped Motor Behaviors and Reversal Learning in the BTBR Mouse Model of Autism

BACKGROUND

Autism spectrum disorders (ASD) are a set of neurodevelopmental disorders marked by a lack of social interaction, restrictive interests, and repetitive behaviors. There is a paucity of pharmacological treatments to reduce core ASD symptoms. Various lines of evidence indicate that reduced brain muscarinic cholinergic receptor activity may contribute to an ASD phenotype.

METHODS

The present experiments examined whether the partial M1 muscarinic receptor agonist, 5-(3-ethyl-1,2,4-oxadiazol-5-yl)-1,4,5,6-tetrahydropyrimidine hydrochloride (CDD-0102A), alleviates behavioral flexibility deficits and/or stereotyped motor behaviors in the BTBR mouse model of autism. Behavioral flexibility was tested using a reversal learning test. Stereotyped motor behaviors were measured by eliciting digging behavior after removal of nesting material in a home cage and by measuring repetitive grooming.

RESULTS

CDD-0102A (0.2 and 0.6 mg/kg but not 1.2 mg/kg) injected prior to reversal learning attenuated a deficit in BTBR mice but did not affect performance in B6 mice. Acute CDD-0102A treatment (1.2 and 3 mg/kg) reduced self-grooming in BTBR mice and reduced digging behavior in B6 and BTBR mice. The M1 muscarinic receptor antagonist VU0255035 (3 mg/kg) blocked the effect of CDD-0102A on grooming behavior. Chronic treatment with CDD-0102A (1.2 mg/kg) attenuated self-grooming and digging behavior in BTBR mice. Direct CDD-0102A infusions (1 µg) into the dorsal striatum reduced elevated digging behavior in BTBR mice. In contrast, CDD-0102A injections in the frontal cortex were not effective.

CONCLUSIONS

The results suggest that treatment with a partial M1 muscarinic receptor agonist may reduce repetitive behaviors and restricted interests in autism in part by stimulating striatal M1 muscarinic receptors.

Psilocybin therapy increases cognitive and neural flexibility in patients with major depressive disorder

Psilocybin has shown promise for the treatment of mood disorders, which are often accompanied by cognitive dysfunction including cognitive rigidity. Recent studies have proposed neuropsychoplastogenic effects as mechanisms underlying the enduring therapeutic effects of psilocybin. In an open-label study of 24 patients with major depressive disorder, we tested the enduring effects of psilocybin therapy on cognitive flexibility (perseverative errors on a set-shifting task), neural flexibility (dynamics of functional connectivity or dFC via functional magnetic resonance imaging), and neurometabolite concentrations (via magnetic resonance spectroscopy) in brain regions supporting cognitive flexibility and implicated in acute psilocybin effects (e.g., the anterior cingulate cortex, or ACC). Psilocybin therapy increased cognitive flexibility for at least 4 weeks post-treatment, though these improvements were not correlated with the previously reported antidepressant effects. One week after psilocybin therapy, glutamate and N-acetylaspartate concentrations were decreased in the ACC, and dFC was increased between the ACC and the posterior cingulate cortex (PCC). Surprisingly, greater increases in dFC between the ACC and PCC were associated with less improvement in cognitive flexibility after psilocybin therapy. Connectome-based predictive modeling demonstrated that baseline dFC emanating from the ACC predicted improvements in cognitive flexibility. In these models, greater baseline dFC was associated with better baseline cognitive flexibility but less improvement in cognitive flexibility. These findings suggest a nuanced relationship between cognitive and neural flexibility. Whereas some enduring increases in neural dynamics may allow for shifting out of a maladaptively rigid state, larger persisting increases in neural dynamics may be of less benefit to psilocybin therapy.

Cariprazine alleviates core behavioral deficits in the prenatal valproic acid exposure model of autism spectrum disorder

RATIONALE

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficits in social communication and interaction and restricted, repetitive behaviors. The unmet medical need in ASD is considerable since there is no approved pharmacotherapy for the treatment of these deficits in social communication, interaction, and behavior. Cariprazine, a dopamine D₃-preferring D₃/D₂ receptor partial agonist, is already approved for the treatment of schizophrenia and bipolar I disorder in adults; investigation in patients with ASD is warranted.

OBJECTIVES

The aim of this study was to investigate the effects of cariprazine, compared with risperidone and aripiprazole, in the rat prenatal valporic acid (VPA) exposure model on behavioral endpoints representing the core and associated symptoms of ASD.

METHODS

To induce the ASD model, time-mated Wistar rat dams were treated with VPA during pregnancy. Male offspring were assigned to groups and studied in a behavioral test battery at different ages, employing social play, open field, social approach-avoidance, and social recognition memory tests. Animals were dosed orally, once a day for 8 days, with test compounds (cariprazine, risperidone, aripiprazole) or vehicle before behavioral assessment.

RESULTS

Cariprazine showed dose-dependent efficacy on all behavioral endpoints. In the social play paradigm, only cariprazine was effective. On the remaining behavioral endpoints, including the reversal of hyperactivity, risperidone and aripiprazole displayed similar efficacy to cariprazine.

CONCLUSIONS

In the present study, cariprazine effectively reversed core behavioral deficits and hyperactivity present in juvenile and young adult autistic-like rats. These findings indicate that cariprazine may be useful in the treatment of ASD symptoms.

Different neurocognitive profiles of risperidone and aripiprazole in the FIRST episode of psychosis: A 3-year follow-up comparison

Cognitive deficits have been recognized as a central feature of schizophrenia spectrum disorders. These deficits are often related to more severe negative symptoms, as well as a poorer adjustment in social functioning. Therefore, it is important to improve cognitive performance from the onset of the disease. In this study, we compared the effects of two atypical antipsychotics, risperidone and aripiprazole, on cognition. The data used in the present investigation were obtained from a large epidemiological cohort of patients with a first episode of psychosis who were treated in a longitudinal intervention programme. The patients included in the program were randomized to treatment with risperidone or aripiprazole and were assessed for cognitive function at baseline and 3 years later. The final sample consisted of 115 patients, 55 of whom were initially assigned to risperidone and 60 to aripiprazole. The groups did not show significant differences in their sociodemographic or clinical characteristics at intake. Longitudinal analyses showed that risperidone-treated patients improved in the processing speed domain at the 3-year follow-up, while the aripiprazole group showed better scores for the executive function domain. Our study shows slight differences between the effects of risperidone and aripiprazole on cognition, suggesting different patterns of efficacy on cognitive function that may warrant more thorough research to determine the beneficial effects of these drugs on cognition. Future studies should evaluate the effects of these treatments over longer follow-up periods using standardized tools for the assessment of cognitive function.

The selective 5-HT2A receptor agonist 25CN-NBOH does not affect reversal learning in mice

Psychedelic 5-hydroxytryptamine 2A receptor (5-HT2AR) agonists are showing promise in the treatment of psychiatric disorders, such as treatment-resistant depression and anxiety. Human studies suggest that enhanced cognitive flexibility may contribute to their clinical efficacy. Both improvement and impairment of cognitive flexibility has been reported with 5-HT2AR ligands, making the link between 5-HT2AR pharmacology and cognitive flexibility equivocal. We tested the selective 5-HT2AR agonist 25CN-NBOH in healthy male C57BL/6JOlaHsd mice in a touchscreen-based mouse reversal learning test. No effects were observed on acquisition of the new stimulus-reward contingency, learning errors, or perseverative responses during reversal. Our results suggest that 25CN-NBOH does not affect reversal learning in the schedule used in this study.

Impact of specific serotonin receptor modulation on behavioral flexibility

Serotonin (5-HT) is known to play a critical role in regulation of essential neural processes, whereas more recent research highlights serotonin's modulatory effects on cognition and executive functioning. Current examinations have identified specific serotonin receptors for their direct impact on behavioral flexibility. Providing definitive evidence for the impact of specific receptor targets on behavioral flexibility is difficult, due to the range of behavioral tests used. Due to limited studies and the sheer amount of different serotonin receptor targets, beginning to bring these studies together is important for the field. Our current review of the literature aims to differentiate how modulation of specific 5-HT receptors affects behavioral flexibility. Although more studies have examined 5-HT_2A, 5-HT_2C, and 5-HT₆ receptors, it is unclear why this is the case. Above all, there are some paradoxical results pertaining to these receptor targets. There is a clear distinction between 5-HT_2A and 5-HT_2C, which conveys that these two receptor subtypes have inverse effects when compared to each other. In addition, some findings support one another, such as upregulation of 5-HT₆ receptors impairs flexibility, while blockade alleviates this impairment in both drug-induced and disease model rodent studies. Further understanding how modulatory effects of specific 5-HT receptors impact behavioral flexibility is imperative to advance the development of new therapeutics for neuropsychiatric disorders afflicted by behavioral inflexibility.

Hidden talents: Poly (I:C)-induced maternal immune activation improves mouse visual discrimination performance and reversal learning in a sex-dependent manner

While there is a strong focus on the negative consequences of maternal immune activation (MIA) on developing brains, very little attention is directed towards potential advantages of early life challenges. In this study, we utilized a polyinosine-polycytidylic acid (poly(I:C)) MIA model to test visual pairwise discrimination (PD) and reversal learning (RL) in mice using touchscreen technology. Significant sex differences emerged in that MIA reduced the latency for males to make a correct choice in the PD task while females reached criterion sooner, made fewer errors, and utilized fewer correction trials in RL compared to saline controls. These surprising improvements were accompanied by the sex-specific upregulation of several genes critical to cognitive functioning, indicative of compensatory plasticity in response to MIA. In contrast, when exposed to a 'two-hit' stress model (MIA + loss of the social component of environmental enrichment [EE]), mice did not display anhedonia but required an increased number of PD and RL correction trials. These animals also had significant reductions of CamK2a mRNA in the prefrontal cortex. Appropriate functioning of synaptic plasticity, via mediators such as this protein kinase and others, are critical for behavioral flexibility. Although EE has been implicated in, delaying the appearance of symptoms associated with certain brain disorders, these findings are in line with evidence that it also makes individuals more vulnerable to its loss. Overall, with the right 'dose', early life stress exposure can confer at least some functional advantages, which are lost when the number or magnitude of these exposures become too great.

Neural Mechanisms Underlying Repetitive Behaviors in Rodent Models of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is comprised of several conditions characterized by alterations in social interaction, communication, and repetitive behaviors. Genetic and environmental factors contribute to the heterogeneous development of ASD behaviors. Several rodent models display ASD-like phenotypes, including repetitive behaviors. In this review article, we discuss the potential neural mechanisms involved in repetitive behaviors in rodent models of ASD and related neuropsychiatric disorders. We review signaling pathways, neural circuits, and anatomical alterations in rodent models that display robust stereotypic behaviors. Understanding the mechanisms and circuit alterations underlying repetitive behaviors in rodent models of ASD will inform translational research and provide useful insight into therapeutic strategies for the treatment of repetitive behaviors in ASD and other neuropsychiatric disorders.

Cariprazine alleviates core behavioral deficits in the prenatal valproic acid exposure model of autism spectrum disorder

RATIONALE

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficits in social communication and interaction and restricted, repetitive behaviors. The unmet medical need in ASD is considerable since there is no approved pharmacotherapy for the treatment of these deficits in social communication, interaction, and behavior. Cariprazine, a dopamine D₃-preferring D₃/D₂ receptor partial agonist, is already approved for the treatment of schizophrenia and bipolar I disorder in adults; investigation in patients with ASD is warranted.

OBJECTIVES

The aim of this study was to investigate the effects of cariprazine, compared with risperidone and aripiprazole, in the rat prenatal valporic acid (VPA) exposure model on behavioral endpoints representing the core and associated symptoms of ASD.

METHODS

To induce the ASD model, time-mated Wistar rat dams were treated with VPA during pregnancy. Male offspring were assigned to groups and studied in a behavioral test battery at different ages, employing social play, open field, social approach-avoidance, and social recognition memory tests. Animals were dosed orally, once a day for 8 days, with test compounds (cariprazine, risperidone, aripiprazole) or vehicle before behavioral assessment.

RESULTS

Cariprazine showed dose-dependent efficacy on all behavioral endpoints. In the social play paradigm, only cariprazine was effective. On the remaining behavioral endpoints, including the reversal of hyperactivity, risperidone and aripiprazole displayed similar efficacy to cariprazine.

CONCLUSIONS

In the present study, cariprazine effectively reversed core behavioral deficits and hyperactivity present in juvenile and young adult autistic-like rats. These findings indicate that cariprazine may be useful in the treatment of ASD symptoms.

Subarachnoid hemorrhage in C57BL/6J mice increases motor stereotypies and compulsive-like behaviors

OBJECTIVE

Long-term behavioral, mood, and cognitive deficits affect over 30% of patients with subarachnoid hemorrhage (SAH). The aim of the present study was to examine the neurobehavioral outcomes following endovascular perforation induced SAH in mice.

METHODS

C57BL/6 J (B6) mice were exposed to endovascular perforation induced SAH or control surgery. Three weeks later, mice received a series of behavioral tests, e.g. motor function, stereotypy, learning, memory, behavioral flexibility, depression and anxiety. The immunohistologic experiment examined neuronalloss in the cortex following SAH.

RESULTS

SAH mice exhibited increased marble burying and nestlet shredding compared to that of control mice. Although SAH did not affect memory, learning or reversal learning,mice displayed greater overall object exploration in the novel object recognition test, as well as elevated perseveration during probabilistic reversal learning.In the forced swim and open field tests, SAH mice performed comparably to that of control mice. However, SAH mice exhibited an increased frequency in 'jumping' behavior in the open field test. Histological analyses revealed reduced neuron density in the parietal-entorhinal cortices of SAH mice on the injured side compared to that of control mice.

DISCUSSION

The findings suggest that parietal-entorhinal damage from SAH increases stereotyped motor behaviors and 'compulsive-like' behaviors without affecting cognition (learning and memory) or mood (anxiety and depression). This model can be used to better understand the neuropathophysiology following SAH that contributes to behavioral impairments in survivors with no gross sensory-motor deficits.

The relationship between monoaminergic gene expression, learning, and optimism in red junglefowl chicks

Intra-species cognitive variation is commonly observed, but explanations for why individuals within a species differ in cognition are still understudied and not yet clear. Cognitive processes are likely influenced by genetic differences, with genes in the monoaminergic systems predicted to be important. To explore the potential role of these genes in association with individual variation in cognition, we exposed red junglefowl (Gallus gallus) chicks to behavioural assays measuring variation in learning (discriminative learning, reversal learning, and cognitive flexibility) and optimism (measured in a cognitive judgement bias test). Following this, we analysed prefrontal cortex gene expression of several dopaminergic and serotonergic genes in these chicks. Of our explored genes, serotonin receptor genes 5HT2A and 5HT2B, and dopaminergic receptor gene DRD1 were associated with measured behaviour. Chicks that had higher 5HT2A were less flexible in the reversal learning task, and chicks with higher 5HT2B also tended to be less cognitively flexible. Additionally, chicks with higher DRD1 were more optimistic, whilst chicks with higher 5HT2A tended to be less optimistic. These results suggest that the serotonergic and dopaminergic systems are linked to observed cognitive variation, and, thus, individual differences in cognition can be partially explained by variation in brain gene expression.

Separating Probability and Reversal Learning in a Novel Probabilistic Reversal Learning Task for Mice

The exploration/exploitation tradeoff – pursuing a known reward vs. sampling from lesser known options in the hope of finding a better payoff – is a fundamental aspect of learning and decision making. In humans, this has been studied using multi-armed bandit tasks. The same processes have also been studied using simplified probabilistic reversal learning (PRL) tasks with binary choices. Our investigations suggest that protocols previously used to explore PRL in mice may prove beyond their cognitive capacities, with animals performing at a no-better-than-chance level. We sought a novel probabilistic learning task to improve behavioral responding in mice, whilst allowing the investigation of the exploration/exploitation tradeoff in decision making. To achieve this, we developed a two-lever operant chamber task with levers corresponding to different probabilities (high/low) of receiving a saccharin reward, reversing the reward contingencies associated with levers once animals reached a threshold of 80% responding at the high rewarding lever. We found that, unlike in existing PRL tasks, mice are able to learn and behave near optimally with 80% high/20% low reward probabilities. Altering the reward contingencies towards equality showed that some mice displayed preference for the high rewarding lever with probabilities as close as 60% high/40% low. Additionally, we show that animal choice behavior can be effectively modelled using reinforcement learning (RL) models incorporating learning rates for positive and negative prediction error, a perseveration parameter, and a noise parameter. This new decision task, coupled with RL analyses, advances access to investigate the neuroscience of the exploration/exploitation tradeoff in decision making.

The 5-hydroxytryptamine 2A receptor agonists DOI and 25CN-NBOH decrease marble burying and reverse 8-OH-DPAT-induced deficit in spontaneous alternation

5-Hydroxytryptamine 2A receptor (5-HT_2AR) agonist psychedelics are increasingly recognized as potentially useful treatments of psychiatric disorders, such as obsessive-compulsive disorder, depression, anxiety, and drug dependence. There is limited understanding of the way they exert their therapeutic action, but inhibition of rigid behavior and cognition has been suggested as a key factor. To examine the role of 5-HT_2ARs in modulating repetitive behavior, we tested two 5-HT_2AR agonists, DOI, and the selective 25CN-NBOH, in two mouse tests of compulsive-like behavior. Using adult C57BL/6JOlaHsd male mice, we examined the effects of the two compounds on digging behavior in the marble burying test and on 8-OH-DPAT-disrupted spontaneous alternation behavior in the Y-maze. Both compounds dose-dependently decreased digging behavior in the marble burying test, indicating anti-compulsivity effects, which were not related to non-specific locomotor inhibition. Both 5-HT_2AR agonists also reversed 8-OH-DPAT-reduced alternation ratio in the spontaneous alternation behavior test, although the effects were less pronounced than in the marble burying test. This suggests that the 5-HT_2AR promotes exploratory behavior, but that the deficit produced by 8-OH-DPAT is too excessive to be fully reversed by 5-HT_2AR agonists. This study shows that agonism of 5-HT_2AR reduces repetitive behavioral patterns, supporting the theory that this is a potential new treatment approach to disorders of cognitive or behavioral inflexibility. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

Deep learning of spontaneous arousal fluctuations detects early cholinergic defects across neurodevelopmental mouse models and patients

Neurodevelopmental spectrum disorders like autism (ASD) are diagnosed, on average, beyond age 4 y, after multiple critical periods of brain development close and behavioral intervention becomes less effective. This raises the urgent need for quantitative, noninvasive, and translational biomarkers for their early detection and tracking. We found that both idiopathic (BTBR) and genetic (CDKL5- and MeCP2-deficient) mouse models of ASD display an early, impaired cholinergic neuromodulation as reflected in altered spontaneous pupil fluctuations. Abnormalities were already present before the onset of symptoms and were rescued by the selective expression of MeCP2 in cholinergic circuits. Hence, we trained a neural network (ConvNetACh) to recognize, with 97% accuracy, patterns of these arousal fluctuations in mice with enhanced cholinergic sensitivity (LYNX1-deficient). ConvNetACh then successfully detected impairments in all ASD mouse models tested except in MeCP2-rescued mice. By retraining only the last layers of ConvNetACh with heart rate variation data (a similar proxy of arousal) directly from Rett syndrome patients, we generated ConvNetPatients, a neural network capable of distinguishing them from typically developing subjects. Even with small cohorts of rare patients, our approach exhibited significant accuracy before (80% in the first and second year of life) and into regression (88% in stage III patients). Thus, transfer learning across species and modalities establishes spontaneous arousal fluctuations combined with deep learning as a robust noninvasive, quantitative, and sensitive translational biomarker for the rapid and early detection of neurodevelopmental disorders before major symptom onset.

Citalopram attenuates social behavior deficits in the BTBR T+Itpr3tf/J mouse model of autism

Autism spectrum disorder (ASD) is diagnosed by two core symptoms: impaired social communication and the presence of repetitive, stereotyped behaviors and/or restricted interests. Alterations in serotonergic signaling are involved in the genesis of ASD. Selective serotonin reuptake inhibitors (SSRIs) have been reported to reduce repetitive behaviors and rescue social deficits in ASD mouse models and patients. In the present study, we examined the potential of citalopram (a representative selective serotonin reuptake inhibitor) on sociability and repetitive behaviors in the BTBR T⁺Itpr3^tf/J (BTBR) mouse model of ASD. We found that the deficits of sociability in the BTBR mice were reversed by a 20 mg/kg dose of citalopram treatment without any adverse effects on locomotor activity or anxiety level. In addition, both high (20 mg/kg) and low (10 mg/kg) doses decreased the repetitive behavior of marble burying but did not affect self-grooming behavior. Furthermore, both doses were shown to have antidepressant-like activity in both the B6 and the BTBR mice in the tail suspension test. Taken together, these findings further demonstrate that citalopram can alleviate behavioral abnormalities in the BTBR autism model and lend support to the hypothesis that SSRIs may be potential therapeutic drugs for the treatment of behavioral dysfunctions in ASD.

Effect of risperidone on proliferation and apoptosis of MC3T3-E1 cells

This aim of this study was to assess the molecular mechanism of osteoporosis in schizophrenia patients with risperidone use. Here, we investigated the effects of risperidone on cellular proliferation and apoptosis of a preosteoblast cell line, MC3T3-E1. Cell viability and apoptotic rate of MC3T3-E1 were detected by cell counting kit-8 and flow cytometry at a serial dose of risperidone and at different time points, respectively. Bone transformation relevant gene serum osteocalcin (BGP), collagen 1, tumor necrosis factor-α (TNF-α), osteoprotegerin (OPG), and receptor activator of nuclear factor-κB ligand (RANKL) mRNA levels were determined by real-time PCR (qPCR). Their protein expression patterns were evaluated using western blot. The results revealed that risperidone dramatically inhibited MC3T3-E1 cell proliferation in a dose-dependent manner. It also significantly induced MC3T3-E1 cell apoptosis. TNF-α gene and protein levels were greatly enhanced after risperidone treatment. In contrast, BGP, collagen 1, OPG, and RANKL gene and protein levels were markedly downregulated. Our study indicated that risperidone suppressed MC3T3-E1 cell proliferation and induced apoptosis. It also regulated BGP gene and protein expression.

Maternal immune activation impairs cognitive flexibility and alters transcription in frontal cortex

BACKGROUND

Epidemiological studies suggest that the risk of neurodevelopmental disorders such as autism spectrum disorder (ASD) and schizophrenia is increased by prenatal exposure to viral or bacterial infection during pregnancy. It is still unclear how activation of the maternal immune response interacts with underlying genetic factors to influence observed ASD phenotypes.

METHODS

The current study investigated how maternal immune activation (MIA) in mice impacts gene expression in the frontal cortex in adulthood, and how these molecular changes relate to deficits in cognitive flexibility and social behavior, and increases in repetitive behavior that are prevalent in ASD. Poly(I:C) (20 mg/kg) was administered to dams on E12.5 and offspring were tested for social approach behavior, repetitive grooming, and probabilistic reversal learning in adulthood (n = 8 vehicle; n = 9 Poly(I:C)). We employed next-generation high-throughput mRNA sequencing (RNA-seq) to comprehensively investigate the transcriptome profile in frontal cortex of adult offspring of Poly(I:C)-exposed dams.

RESULTS

Exposure to poly(I:C) during gestation impaired probabilistic reversal learning and decreased social approach in MIA offspring compared to controls. We found long-term effects of MIA on expression of 24 genes, including genes involved in glutamatergic neurotransmission, mTOR signaling and potassium ion channel activity. Correlations between gene expression and specific behavioral measures provided insight into genes that may be responsible for ASD-like behavioral alterations.

CONCLUSIONS

These findings suggest that MIA can lead to impairments in cognitive flexibility in mice similar to those exhibited in ASD individuals, and that these impairments are associated with altered gene expression in frontal cortex.

Beneficial and adverse effects of antipsychotic medication on cognitive flexibility are related to COMT genotype in first episode psychosis

This study evaluated the ability to flexibly shift cognitive set and to consistently maintain a new response preference using the Penn Conditional Exclusion Test (PCET). The relationship of performance errors with catechol-O-methyltransferase (COMT) rs4680 (Val158Met) genotype (Met carriers vs. Val homozygotes) on test performance before and after antipsychotic treatment in 32 first episode psychosis (FEP) patients was examined. After treatment, patients demonstrated a mixture of beneficial and adverse cognitive outcomes that varied in relation to COMT genotype. Met carriers showed decreased perseverative and regressive errors, reflecting improved cognitive flexibility and enhanced stability of behavioral preferences, respectively. In contrast, Val homozygotes exhibited an increase in regressive errors after treatment. These findings suggest that Val homozygotes may be vulnerable to adverse effects of antipsychotic medication on cognitive processes that maintain consistent adaptive response preferences, an ability linked to the striatum in rodent models.

From bedside to bench and back: Translating ASD models

Autism spectrum disorders (ASD) represent a heterogeneous group of disorders defined by deficits in social interaction/communication and restricted interests, behaviors, or activities. Models of ASD, developed based on clinical data and observations, are used in basic science, the "bench," to better understand the pathophysiology of ASD and provide therapeutic options for patients in the clinic, the "bedside." Translational medicine creates a bridge between the bench and bedside that allows for clinical and basic science discoveries to challenge one another to improve the opportunities to bring novel therapies to patients. From the clinical side, biomarker work is expanding our understanding of possible mechanisms of ASD through measures of behavior, genetics, imaging modalities, and serum markers. These biomarkers could help to subclassify patients with ASD in order to better target treatments to a more homogeneous groups of patients most likely to respond to a candidate therapy. In turn, basic science has been responding to developments in clinical evaluation by improving bench models to mechanistically and phenotypically recapitulate the ASD phenotypes observed in clinic. While genetic models are identifying novel therapeutics targets at the bench, the clinical efforts are making progress by defining better outcome measures that are most representative of meaningful patient responses. In this review, we discuss some of these challenges in translational research in ASD and strategies for the bench and bedside to bridge the gap to achieve better benefits to patients.

Selective effects of 5-HT2C receptor modulation on performance of a novel valence-probe visual discrimination task and probabilistic reversal learning in mice

RATIONALE

Dysregulation of the serotonin (5-HT) system is a pathophysiological component in major depressive disorder (MDD), a condition closely associated with abnormal emotional responsivity to positive and negative feedback. However, the precise mechanism through which 5-HT tone biases feedback responsivity remains unclear. 5-HT2C receptors (5-HT2CRs) are closely linked with aspects of depressive symptomatology, including abnormalities in reinforcement processes and response to stress. Thus, we aimed to determine the impact of 5-HT2CR function on response to feedback in biased reinforcement learning.

METHODS

We used two touchscreen assays designed to assess the impact of positive and negative feedback on probabilistic reinforcement in mice, including a novel valence-probe visual discrimination (VPVD) and a probabilistic reversal learning procedure (PRL). Systemic administration of a 5-HT2CR agonist and antagonist resulted in selective changes in the balance of feedback sensitivity bias on these tasks.

RESULTS

Specifically, on VPVD, SB 242084, the 5-HT2CR antagonist, impaired acquisition of a discrimination dependent on appropriate integration of positive and negative feedback. On PRL, SB 242084 at 1 mg/kg resulted in changes in behaviour consistent with reduced sensitivity to positive feedback. In contrast, WAY 163909, the 5-HT2CR agonist, resulted in changes associated with increased sensitivity to positive feedback and decreased sensitivity to negative feedback.

CONCLUSIONS

These results suggest that 5-HT2CRs tightly regulate feedback sensitivity bias in mice with consequent effects on learning and cognitive flexibility and specify a framework for the influence of 5-HT2CRs on sensitivity to reinforcement.

Insulin-Like Growth Factor II Targets the mTOR Pathway to Reverse Autism-Like Phenotypes in Mice

Autism spectrum disorder (ASD) is a developmental disability characterized by impairments in social interaction and repetitive behavior, and is also associated with cognitive deficits. There is no current treatment that can ameliorate most of the ASD symptomatology; thus, identifying novel therapies is urgently needed. We used male BTBR T⁺Itpr3^tf /J (BTBR) mice, a model that reproduces most of the core behavioral phenotypes of ASD, to test the effects of systemic administration of insulin-like growth factor II (IGF-II), a polypeptide that crosses the blood-brain barrier and acts as a cognitive enhancer. We show that systemic IGF-II treatments reverse the typical defects in social interaction, cognitive/executive functions, and repetitive behaviors reflective of ASD-like phenotypes. In BTBR mice, IGF-II, via IGF-II receptor, but not via IGF-I receptor, reverses the abnormal levels of the AMPK-mTOR-S6K pathway and of active translation at synapses. Thus, IGF-II may represent a novel potential therapy for ASD.SIGNIFICANCE STATEMENT Currently, there is no effective treatment for autism spectrum disorder (ASD), a developmental disability affecting a high number of children. Using a mouse model that expresses most of the key core as well as associated behavioral deficits of ASD, that are, social, cognitive, and repetitive behaviors, we report that a systemic administration of the polypeptide insulin-like growth factor II (IGF-II) reverses all these deficits. The effects of IGF-II occur via IGF-II receptors, and not IGF-I receptors, and target both basal and learning-dependent molecular abnormalities found in several ASD mice models, including those of identified genetic mutations. We suggest that IGF-II represents a potential novel therapeutic target for ASD.

16p11.2 deletion syndrome mice perseverate with active coping response to acute stress - rescue by blocking 5-HT2A receptors

In humans a chromosomal hemideletion of the 16p11.2 region results in variable neurodevelopmental deficits including developmental delay, intellectual disability, and features of autism spectrum disorder (ASD). Serotonin is implicated in ASD but its role remains enigmatic. In this study we sought to determine if and how abnormalities in serotonin neurotransmission could contribute to the behavioral phenotype of the 16p11.2 deletion syndrome in a mouse model (Del mouse). As ASD is frequently associated with altered response to acute stress and stress may exacerbate repetitive behavior in ASD, we studied the Del mouse behavior in the context of an acute stress using the forced swim test, a paradigm well characterized with respect to serotonin. Del mice perseverated with active coping (swimming) in the forced swim test and failed to adopt passive coping strategies with time as did their wild-type littermates. Analysis of monoamine content by HPLC provided evidence for altered endogenous serotonin neurotransmission in Del mice while there was no effect of genotype on any other monoamine. Moreover, we found that Del mice were highly sensitive to the 5-HT2A antagonists M100907, which at a dose of 0.1 mg/kg normalized their level of active coping and restored the gradual shift to passive coping in the forced swim test. Supporting evidence for altered endogenous serotonin signaling was provided by observations of additional ligand effects including altered forebrain Fos expression. Taken together, these observations indicate notable changes in endogenous serotonin signaling in 16p11.2 deletion mice and support the therapeutic utility of 5-HT2A receptor antagonists.

The adenosine A2A receptor agonist, CGS 21680, attenuates a probabilistic reversal learning deficit and elevated grooming behavior in BTBR mice

Restricted interests and repetitive behaviors (RRBs) are a defining feature of autism spectrum disorder (ASD). To date there are limited options for treating this core symptomology. Treatments that stimulate adenosine A_2A receptors may represent a promising approach for reducing RRBs in ASD. This is because A_2A receptors are expressed on striatal neurons of the basal ganglia indirect pathway. Under activation of this pathway has been associated with RRBs while activation of A_2A receptors leads to increased activity of the indirect basal ganglia pathway. The present studies investigated whether acute, systemic treatment with CGS21680, an A_2A receptor agonist attenuates elevated self-grooming and a probabilistic reversal learning deficit in the BTBR T+ Itpr3^tf /J (BTBR) mouse model of idiopathic autism. The effects of this treatment were also investigated in C57BL/6J (B6) mice as a comparison strain. Using a spatial reversal learning test with 80/20 probabilistic feedback, comparable to one in which ASD individuals exhibit deficits, CGS 21680 (0.005 and 0.01mg/kg) attenuated a reversal learning deficit in BTBR mice. Enhancement in probabilistic reversal learning performance resulted from CGS 21680 improving the consistent maintenance of new adaptive behavioral choice patterns after reversal. CGS 21680 at 0.01 mg, but not 0.005 mg, also reduced self-grooming behavior in BTBR mice. CGS 21680 did not affect self-grooming or reversal learning in B6 mice. These findings demonstrate that A_2A receptor agonists may be a promising receptor target in the treatment of RRBs in ASD. Autism Res 2018, 11: 223-233. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

The present experiments determined whether the drug, CGS 21680, that facilitates activation of adenosine A_2A receptors in the brain, would reduce repetitive and inflexible behaviors in the BTBR mouse model of idiopathic autism. CGS 21680 treatment in BTBR mice reduced repetitive and inflexible behaviors. In the control C57BL/6J (B6) mouse strain, CGS 21680 did not affect performance. These findings suggest that stimulation of brain adenosine A_2A receptors may be a promising therapeutic strategy in ASD.

Risperidone and aripiprazole alleviate prenatal valproic acid-induced abnormalities in behaviors and dendritic spine density in mice

RATIONALE

Rodents exposed prenatally to valproic acid (VPA) exhibit autism spectrum disorder (ASD)-like behavioral abnormalities. We recently found that prenatal VPA exposure causes hypofunction of the prefrontal dopaminergic system in mice. This suggests that the dopaminergic system may be a potential pharmacological target for treatment of behavioral abnormalities in ASD patients.

OBJECTIVES

In the present study, we examined the effects of antipsychotic drugs, which affect the dopaminergic system, on the social interaction deficits, recognition memory impairment, and reduction in dendritic spine density in the VPA mouse model of ASD.

RESULTS

Both acute and chronic administrations of the atypical antipsychotic drugs risperidone and aripiprazole increased prefrontal dopamine (DA) release, while the typical antipsychotic drug haloperidol did not. Chronic risperidone and aripiprazole, but not haloperidol, increased the expression of c-Fos in the prefrontal cortex, although they all increased c-Fos expression in the striatum. Chronic, but not acute, administrations of risperidone and aripiprazole improved the VPA-induced social interaction deficits and recognition memory impairment, as well as the reduction in dendritic spine density in the prefrontal cortex and hippocampus. In contrast, chronic administration of haloperidol did not ameliorate VPA-induced abnormalities in behaviors and dendritic spine density.

CONCLUSIONS

These findings indicate that chronic risperidone and aripiprazole treatments improve VPA-induced abnormalities in behaviors and prefrontal dendritic spine density, which may be mediated by repeated elevation of extracellular DA in the prefrontal cortex. Our results also imply that loss of prefrontal dendritic spines may be involved in the abnormal behaviors in the VPA mouse model of ASD.

Risperidone and aripiprazole alleviate prenatal valproic acid-induced abnormalities in behaviors and dendritic spine density in mice

RATIONALE

Rodents exposed prenatally to valproic acid (VPA) exhibit autism spectrum disorder (ASD)-like behavioral abnormalities. We recently found that prenatal VPA exposure causes hypofunction of the prefrontal dopaminergic system in mice. This suggests that the dopaminergic system may be a potential pharmacological target for treatment of behavioral abnormalities in ASD patients.

OBJECTIVES

In the present study, we examined the effects of antipsychotic drugs, which affect the dopaminergic system, on the social interaction deficits, recognition memory impairment, and reduction in dendritic spine density in the VPA mouse model of ASD.

RESULTS

Both acute and chronic administrations of the atypical antipsychotic drugs risperidone and aripiprazole increased prefrontal dopamine (DA) release, while the typical antipsychotic drug haloperidol did not. Chronic risperidone and aripiprazole, but not haloperidol, increased the expression of c-Fos in the prefrontal cortex, although they all increased c-Fos expression in the striatum. Chronic, but not acute, administrations of risperidone and aripiprazole improved the VPA-induced social interaction deficits and recognition memory impairment, as well as the reduction in dendritic spine density in the prefrontal cortex and hippocampus. In contrast, chronic administration of haloperidol did not ameliorate VPA-induced abnormalities in behaviors and dendritic spine density.

CONCLUSIONS

These findings indicate that chronic risperidone and aripiprazole treatments improve VPA-induced abnormalities in behaviors and prefrontal dendritic spine density, which may be mediated by repeated elevation of extracellular DA in the prefrontal cortex. Our results also imply that loss of prefrontal dendritic spines may be involved in the abnormal behaviors in the VPA mouse model of ASD.

Targets for Drug Therapy for Autism Spectrum Disorder: Challenges and Future Directions

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social communication and interaction and restricted, repetitive patterns of behavior, interests, and activities. Various factors are involved in the etiopathogenesis of ASD, including genetic factors, environmental toxins and stressors, impaired immune responses, mitochondrial dysfunction, and neuroinflammation. The heterogeneity in the phenotype among ASD patients and the complex etiology of the condition have long impeded the advancement of the development of pharmacological therapies. In the recent years, the integration of findings from mouse models to human genetics resulted in considerable progress toward the understanding of ASD pathophysiology. Currently, strategies to treat core symptoms of ASD are directed to correct synaptic dysfunctions, abnormalities in central oxytocin, vasopressin, and serotonin neurotransmission, and neuroinflammation. Here, we present a survey of the studies that have suggested molecular targets for drug development for ASD and the state-of-the-art of medicinal chemistry efforts in related areas.