Analyzing grooming microstructure in neurobehavioral experiments

The role of fear and dopamine-striatal pathways in grooming

Fear is a fundamental emotion that triggers rapid and automatic behavioral response. Fear is known to suppress reward-seeking behaviors, interrupt previous activities to prioritize defensive responses and lead to rapid switch to defensive reactions. Dopamine (DA) plays a complicated role in the choice and performance of actions and it has a potential interaction of innate actions with the presence of fear. Here, in a series of experiments we explore the role of the different DA striatal pathways in mediating grooming, an innate behavior comprised of a structured sequence of repetitive actions, with or without the presence of fear. Using chemogenetics, we specifically inhibited the DA pathways projecting to the dorsolateral striatum (DLS), dorsomedial striatum (DMS), and ventral striatum (VS), while mice were engaged in a behavioral paradigm inducing grooming during the presentation of a fear related cue. We found that fear related cues consistently reduced grooming proportions and shortened induced grooming bouts, regardless of DA manipulation, indicating prioritization of freezing behavior in fearful contexts. This also suggests that fear responses may be mediated through pathways independent of DA-based action selection. The role of DA, however, varies depending on the specific striatal pathway. Inhibiting DLS DA input delayed grooming initiation and reduced grooming when competing with freezing. In contrast, DMS DA input had no effect on grooming, while inhibition of VS mesolimbic DA input increased grooming proportions and duration. These findings underscore the distinct and sometimes opposing roles of different DA-striatal pathways in modulating innate behaviors. We discuss potential implications of this duality in DA function for both theoretical and clinical fields.

Ayahuasca Pretreatment Prevents Sepsis-Induced Anxiety-Like Behavior, Neuroinflammation, and Oxidative Stress, and Increases Brain-Derived Neurotrophic Factor

The psychoactive decoction Ayahuasca (AYA) used for therapeutic and religious purposes by indigenous groups and peoples from Amazonian regions produces anti-inflammatory and neuroprotective effects. Thus, it may be useful to attenuate the neuroinflammation and related anxiety- and depressive-like symptoms elicited by inflammatory insults such as sepsis. Rats were pretreated for 3 days with different doses of AYA. Twenty-four hours after, cecal ligation and puncture (CLP) was performed. On days 1-4, post-CLP behavioral tests to assess anxiety-like behavior were performed. After 24-h, neuroinflammation, oxidative stress, myeloperoxidase activity, and mitochondrial metabolism were assessed in the prefrontal cortex (PFC), hippocampus (HP), and cortex. AYA pretreatment increased the time spent in the open arms of the elevated plus maze and prevented the sepsis-induced hyper-grooming and -rearing behavior, suggesting an anxiolytic effect. AYA pretreatment increased the levels of the anti-inflammatory interleukin 4, in the PFC and the cortex, and brain-derived neurotrophic factor in the cortex. Moreover, AYA pretreatment increased myeloperoxidase activity in the PFC and the HP and decreased nitrite/nitrate concentration in the PFC, HP, and cortex of septic rats, suggesting enhanced neutrophil activation and decreased nitric oxide signaling. Furthermore, AYA pretreatment prevented lipid peroxidation in the PFC, HP, and cortex of septic rats as measured by decreased levels of thiobarbituric acid reactive substances. Levels of protein carbonyls and activity of superoxide dismutase, citrate synthase, succinate dehydrogenase, and mitochondrial respiratory chain were not affected. Together, AYA represents a promising approach to prevent sepsis-induced neuroinflammatory and oxidative stress and associated anxiety-like symptoms.

Targeted splicing approach for alleviation of a neurexin 1 haploinsufficiency model

NRXN1 encoding the synaptic organizing protein neurexin 1 (Nrxn1) is among the strongest risk genes for autism spectrum disorders as well as other neuropsychiatric disorders. The most common contributing mutation is a deletion in one allele. While mice lacking one form of the protein, Nrxn1α, have been characterized, information is lacking on animal models with heterozygous deletion of all isoforms, as well as on therapeutic approaches directly targeting Nrxn1. We report that Nrxn1+/- mice with a deletion affecting all isoforms, α, β and γ, show deficits in excitatory synaptic transmission affecting presynaptic and postsynaptic properties at hippocampal CA3-CA1 synapses, and show increased repetitive behaviors. Based on previous studies indicating that exclusion of the insert at Nrxn1 splice site 5 (S5) boosts synaptic transmission, we tested S5 exclusion as a therapeutic approach. Genetic exclusion of S5 in the remaining Nrxn1 allele alleviated the deficits, restoring miniature excitatory postsynaptic current frequency, paired pulse ratio, AMPA/NMDA ratio, and repetitive behaviors to wild type levels and partially restoring Nrxn1 protein level in Nrxn1ΔS5/- compared to Nrxn1+/- mice. These data suggest that S5 exclusion may be a beneficial therapeutic direction in cases of neuropsychiatric disorders involving NRXN1.

GABAergic neurons in central amygdala contribute to orchestrating anxiety-like behaviors and breathing patterns

Anxiety is characterized by dysregulated respiratory reactivity to emotional stimuli. The central amygdala (CeA) is a pivotal structure involved in processing emotional alterations, but its involvement in orchestrating anxiety-like behaviors and specific breathing patterns remains largely unexplored. Our findings demonstrate that the acute restraint stress (ARS) induces anxiety-like behaviors in mice, marked by prolonged grooming time and faster respiratory frequency (RF). Conversely, silencing GABAergic CeA neurons reduces post-ARS anxiety-like behaviors, as well as the associated increases in grooming time and RF. In actively behaving mice, stimulation of GABAergic CeA neurons elicits anxiety-like behaviors, concurrently prolongs grooming time, accelerates RF through a CeA-thalamic paraventricular nucleus (PVT) circuit. In either behaviorally quiescent or anesthetized mice, stimulation of these neurons significantly increases RF but does not induce anxiety-like behaviors through the CeA-lateral parabrachial nucleus (LPBN) circuit. Collectively, GABAergic CeA neurons are instrumental in orchestrating anxiety-like behaviors and breathing patterns primarily through the CeA-PVT and CeA-LPBN circuits, respectively.

Protective effects of alpha-lipoic acid on memory deficit induced by repeated doses of solifenacin in mice: the role of nitro-oxidative stress

Solifenacin (Sol) is one of the most used antimuscarinics for the treatment of bladder dysfunction and there are no conclusive studies on its effects on learning and memory after long-term use. Since substances with antioxidant action, such as alpha-lipoic acid (ALA), have shown protective action in memory deficit and Alzheimer's disease, we decided to study the effects of Sol alone or associated with ALA in behavioral tests of memory and its relation to nitro-oxidative stress in different brain areas. Mice received saline or Sol p.o. for 14 or 28 days. ALA groups received: (a) saline + ALA, (b) Sol for 14 days and Sol + ALA from the 15th to the 28th days and, (c) Sol + ALA for 28 days. Behavioral tests were performed and oxidative changes (lipid peroxidation) and nitrite in the prefrontal cortex (PFC), hippocampus (HC) and striatum (ST) were also determined. Sol produced memory alterations in the mice, reducing the step-down latency and the recognition index in the novel object recognition test. Sol also increased lipid peroxidation in PFC, HC and ST and nitrite levels in the HC. On the other hand, ALA associated with Sol was able to restrict the effects caused by Sol alone, both in relation to nitro-oxidative parameters and in relation to behavioral tests. Taken together, our data suggest that ALA can be administered as an adjunctive drug in patients requiring prolonged use of Sol to mitigate these adverse central nervous system effects. However, clinical studies need to be performed to corroborate preclinical research.

The Utility of Prolonged Chronic Unpredictable Stress to Study the Effects of Chronic Fluoxetine, Eicosapentaenoic Acid, and Lipopolysaccharide on Anxiety-Like Behavior and Hippocampal Transcriptomic Responses in Male Rats

Chronic stress is a common trigger of multiple neuropsychiatric illnesses. Animal models are widely used to study stress-induced brain disorders and their interplay with neuroinflammation and other neuroimmune processes. Here, we apply the prolonged 12-week chronic unpredictable stress (PCUS) model to examine rat behavioral and hippocampal transcriptomic responses to stress and to chronic 4-week treatment with a classical antidepressant fluoxetine, an anti-inflammatory agent eicosapentaenoic acid (EPA), a pro-inflammatory agent lipopolysaccharide and their combinations. Overall, PCUS evoked anxiety-like behavioral phenotype in rats, corrected by chronic fluoxetine (alone or combined with other drugs), and EPA. PCUS also evoked pronounced transcriptomic responses in rat hippocampi, involving > 200 differentially expressed genes. While pharmacological manipulations did not affect hippocampal gene expression markedly, Gpr6, Drd2 and Adora2a were downregulated in stressed rats treated with fluoxetine, EPA and fluoxetine + EPA, suggesting their respective protein products (G protein-coupled receptor 6, dopamine D2 receptor and adenosine A2A receptor) as potential evolutionarily conserved targets under chronic stress. Overall, these findings support the validity of rat PCUS paradigm as a useful model to study stress-related anxiety pathogenesis, and call for further research probing how various conventional and novel drugs may (co)modulate behavioral and neurotranscriptomic biomarkers of chronic stress.

Late development of OCD-like phenotypes in Dlgap1 knockout mice

RATIONALE

Despite variants in the Dlgap1 gene having the two lowest p-value in a genome-wide association study of obsessive compulsive disorder (OCD), previous studies reported the absence of OCD-like phenotypes in Dlgap1 knockout (KO) mice. Since these studies observed behavioral phenotypes only for a short period, development of OCD-like phenotypes in these mice at older ages was still plausible.

OBJECTIVE

To examine the presence or absence of development of OCD-like phenotypes in Dlgap1 KO mice and their responsiveness to fluvoxamine.

METHODS AND RESULTS

Newly produced Dlgap1 KO mice were observed for a year. Modified SHIRPA primary screen in 2-month-old homozygous mutant mice showed only weak signs of anxiety, stress conditions and aggression. At older ages, however, these mutant mice exhibited excessive self-grooming characterized by increased scratching which led to skin lesions. A significant sex difference was observed in this scratching behavior. The penetrance of skin lesions reached 50% at 6-7 months of age and 90% at 12 months of age. In the open-field test performed just after the appearance of these lesions, homozygous mutant mice spent significantly less time in the center, an anxiety-like behavior, than did their wild-type and heterozygous littermates, none and less than 10% of which showed skin lesions at 1 year, respectively. The skin lesions and excessive self-grooming were significantly alleviated by two-week treatment with fluvoxamine.

CONCLUSION

Usefulness of Dlgap1 KO mice as a tool for investigating the pathogenesis of OCD-like phenotypes and its translational relevance was suggested.

Trace amine-associated receptor 1 agonist reduces aggression in brain serotonin-deficient tryptophan hydroxylase 2 knockout rats

Introduction

Aggression and self-harm disproportionately occur in youths preoccupied with social status tracking. These pathological conditions are linked to a serotonin (5-HT) deficit in the brain. Ablation of 5-HT biosynthesis by tryptophan hydroxylase 2 knockout (TPH2-KO) increases aggression in rodents. Remarkably, deletion of the trace amine-associated receptor 1 (TAAR1) results in the same consequences. Unlike the nuanced dynamics of social status cues in young people, the social ranks of rats mainly advance when they dominate larger opponents in combat.

Methods

This study explored whether the potent TAAR1 agonist RO5263397 reduces aggression caused by 5-HT depletion, and whether social rank advancement motivates this aggression. The resident-intruder paradigm was applied with larger and smaller intruders to evaluate whether social rank advancement motivates aggressive behaviors in TPH2-KO rats.

Results

When a smaller intruder was introduced, 5-HT-deficient rats did not differ from wild type littermates. However, when the intruders were larger, the mutants extended their aggressive efforts, refusing to submit. Importantly, RO5263397 selectively abolished this abnormal form of aggression in TPH2-KO rats.

Discussion

Results supported social rank advancement as the main incentive. These data also suggest that TAAR1 is a promising target for the development of new treatments for aggression; independent data also support this conclusion.

AI-powered home cage system for real-time tracking and analysis of rodent behavior

Researchers in animal behavior and neuroscience devote considerable time to observing rodents behavior and physiological responses, with AI monitoring systems reducing personnel workload. This study presents the RodentWatch (RW) system, which leverages deep learning to automatically identify experimental animal behaviors in home cage environments. A single multifunctional camera and edge device are installed inside the animal's home cage, allowing continuous real-time monitoring of the animal's behavior, position, and body temperature for extended periods. We investigated identifying the drinking and resting behaviors of rats, with recognition accuracy enhanced through contextual object labeling and modified non-maximum suppression (NMS) schemes. Two tests-a light cycle change test and a sucrose preference test-were conducted to evaluate the usability of this system in rat behavioral experiments. This system enables notable advancements in image-based behavior recognition for living rodents.

Hypothalamic corticotropin-releasing hormone neurons modulate sevoflurane anesthesia and the post-anesthesia stress responses

General anesthesia (GA) is an indispensable procedure necessary for safely and compassionately administering a significant number of surgical procedures and invasive diagnostic tests. However, the undesired stress response associated with GA causes delayed recovery and even increased morbidity in the clinic. Here, a core hypothalamic ensemble, corticotropin-releasing hormone neurons in the paraventricular nucleus of the hypothalamus (PVHCRH neurons), is discovered to play a role in regulating sevoflurane GA. Chemogenetic activation of these neurons delay the induction of and accelerated emergence from sevoflurane GA, whereas chemogenetic inhibition of PVHCRH neurons accelerates induction and delays awakening. Moreover, optogenetic stimulation of PVHCRH neurons induce rapid cortical activation during both the steady and deep sevoflurane GA state with burst-suppression oscillations. Interestingly, chemogenetic inhibition of PVHCRH neurons relieve the sevoflurane GA-elicited stress response (e.g., excessive self-grooming and elevated corticosterone level). These findings identify PVHCRH neurons modulate states of anesthesia in sevoflurane GA, being a part of anesthesia regulatory network of sevoflurane.

Early-Life Milk αS1-Casein Allergy Induces the Activation of Astrocytes in Mice and Leads to Stress Vulnerability in Adulthood

In recent years, the incidence of food allergies in children has been increasing annually, significantly affecting the quality of life for patients and their families. It has long been suspected that childhood allergies might potentially lead to behavioral and psychological issues in adulthood, but the specific connection remains unclear. In this study, we established a model of young mice allergic to milk αS1-casein, conducted behavioral tests, and employed transcriptomics, immunohistochemistry, Golgi staining, and fecal microbiota transplantation to explore the link between early life allergies and adult psychological problems. The results showed that early life milk protein allergy significantly increased intestinal epithelial permeability in mice, leading to the translocation of gut microbiota metabolites. This process subsequently activated astrocyte lysosomes via SLC15a3, making astrocytes more susceptible. This susceptibility caused mice with early life milk protein allergy to have more activated astrocytes and excessive dendritic spine phagocytosis (normal group: 5.4 ± 1.26 spines/10 μm, allergy group: 3.2 ± 0.92 spines/10 μm) under acute stress in adulthood, leading to anxiety and depressive behaviors.

Experience-dependent grooming microstructure alterations and gastrointestinal dysfunction in the SAPAP3 knockout mouse model of compulsive behaviour

BACKGROUND

Compulsive- and anxiety-like behaviour can be efficiently modelled in SAPAP3 knockout (KO) mice, a preclinical model of relevance to obsessive-compulsive disorder (OCD). Although there is emerging evidence in the clinical literature of gastrointestinal dysfunction in OCD, no previous studies have investigated gut function in preclinical models of relevance to OCD. Similarly, the effects of voluntary exercise (EX) or environmental enrichment (EE) have not yet been explored in this context.

METHOD

We comprehensively phenotyped the SAPAP3 KO mouse model, including the assessment of grooming microstructure, anxiety- and depressive-like behaviour, and gastrointestinal function. Mice were exposed to either standard housing (SH), exercise (EX, provided by giving mice access to running wheels), or environmental enrichment (EE) for 4 weeks to investigate the effects of enriched housing conditions in this animal model relevant to OCD.

FINDINGS

Our study is the first to assess grooming microstructure, perseverative locomotor activity, and gastrointestinal function in SAPAP3 KO mice. We are also the first to report a sexually dimorphic effect of grooming in young-adult SAPAP3 KO mice; along with changes to grooming patterning and indicators of gut dysfunction, which occurred in the absence of gut dysbiosis in this model. Overall, we found no beneficial effects of voluntary exercise or environmental enrichment interventions in this mouse model; and unexpectedly, we revealed a deleterious effect of wheel-running exercise on grooming behaviour. We suspect that the detrimental effects of experimental housing in our study may be indicative of off-target effects of stress-a conclusion that warrants further investigation into the effects of chronic stress in this preclinical model of compulsive behaviour.

Dopaminergic Neurons in Zona Incerta Drives Appetitive Self-Grooming

Dopaminergic (DA) neurons are known to play a key role in controlling behaviors. While DA neurons in other brain regions are extensively characterized, those in zona incerta (ZITH or A13) receive much less attention and their function remains to be defined. Here it is shown that optogenetic stimulation of these neurons elicited intensive self-grooming behaviors and promoted place preference, which can be enhanced by training but cannot be converted into contextual memory. Interestingly, the same stimulation increased DA release to periaqueductal grey (PAG) neurons and local PAG antagonism of DA action reduced the elicited self-grooming. In addition, A13 neurons increased their activity in response to various external stimuli and during natural self-grooming episodes. Finally, monosynaptic retrograde tracing showed that the paraventricular hypothalamus represents one of the major upstream brain regions to A13 neurons. Taken together, these results reveal that A13 neurons are one of the brain sites that promote appetitive self-grooming involving DA release to the PAG.

Decoding Molecular Bases of Rodent Social Hetero-Grooming Behavior Using in Silico Analyses and Bioinformatics Tools

Highly prevalent in laboratory rodents, 'social' hetero-grooming behavior is translationally relevant to modeling a wide range of neuropsychiatric disorders. Here, we comprehensively evaluated all known to date mouse genes linked to aberrant hetero-grooming phenotype, and applied bioinformatics tools to construct a network of their established protein-protein interactions (PPI). We next identified several distinct molecular clusters within this complex network, including neuronal differentiation, cytoskeletal, WNT-signaling and synapsins-associated pathways. Using additional bioinformatics analyses, we further identified 'central' (hub) proteins within these molecular clusters, likely key for mouse hetero-grooming behavior. Overall, a more comprehensive characterization of intricate molecular pathways linked to aberrant rodent grooming may markedly advance our understanding of underlying cellular mechanisms and related neurological disorders, eventually helping discover novel targets for their pharmacological or gene therapy interventions.

Development of an in vitro compound screening system that replicate the in vivo spine phenotype of idiopathic ASD model mice

Autism Spectrum Disorder (ASD) is a developmental condition characterized by core symptoms including social difficulties, repetitive behaviors, and sensory abnormalities. Aberrant morphology of dendritic spines within the cortex has been documented in genetic disorders associated with ASD and ASD-like traits. We hypothesized that compounds that ameliorate abnormalities in spine dynamics might have the potential to ameliorate core symptoms of ASD. Because the morphology of the spine is influenced by signal inputs from other neurons and various molecular interactions, conventional single-molecule targeted drug discovery methods may not suffice in identifying compounds capable of ameliorating spine morphology abnormalities. In this study, we focused on spine phenotypes in the cortex using BTBR T + Itpr3 tf /J (BTBR) mice, which have been used as a model for idiopathic ASD in various studies. We established an in vitro compound screening system using primary cultured neurons from BTBR mice to faithfully represent the spine phenotype. The compound library mainly comprised substances with known target molecules and established safety profiles, including those approved or validated through human safety studies. Following screening of this specialized library containing 181 compounds, we identified 15 confirmed hit compounds. The molecular targets of these hit compounds were largely focused on the 5-hydroxytryptamine receptor (5-HTR). Furthermore, both 5-HT1AR agonist and 5-HT3R antagonist were common functional profiles in hit compounds. Vortioxetine, possessing dual attributes as a 5-HT1AR agonist and 5-HT3R antagonist, was administered to BTBR mice once daily for a period of 7 days. This intervention not only ameliorated their spine phenotype but also alleviated their social behavior abnormality. These results of vortioxetine supports the usefulness of a spine phenotype-based assay system as a potent drug discovery platform targeting ASD core symptoms.

Effects of association between resveratrol and ketamine on behavioral and biochemical analysis in mice

Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a phenol commonly found in grapes and wine, has been associated as protective in experimental models involving alterations in different neurotransmitter systems. However, studies are reporting that resveratrol could have adverse effects. This study evaluated if the association of a low dose of ketamine and resveratrol could induce behavioral manifestations associated with biochemical alterations. Moreover, the effects of treatment with resveratrol and/or ketamine on monoamine oxidase (MAO) activity, oxidative stress markers, and IL-6 levels in the brain were also investigated. Male Swiss mice received a low dose of ketamine (20 mg/kg) for 14 consecutive days, and resveratrol (10, 30, or 100 mg/kg) from day 8 up to day 14 of the experimental period, intraperitoneally. Locomotor, stereotyped behavior, Y-maze, novel recognition object test (NORT), and social interaction were quantified as well as ex vivo analysis of MAO activity, IL-6 levels, and oxidative stress markers (TBARS and total thiol levels) in brain tissues. Ketamine per se reduced the number of bouts of stereotyped behavior on day 8 of the experimental period. Resveratrol per se reduced the locomotor and exploratory activity in the open field, the time of exploration of new objects in the NORT, MAO-A activity in the striatum and increased the IL-6 levels in the cortex. These effects were attenuated when the mice were co-treated with ketamine and resveratrol. There was a decrease in MAO-A activity in the cortex of mice treated with ketamine + resveratrol 100 mg/kg. No significant alterations were found in oxidative stress markers. Resveratrol does not appear to cause summative effects with ketamine on behavioral alterations. However, the effect of resveratrol per se, mainly on locomotor and exploratory activity, should be better investigated.

Ventral zona incerta parvalbumin neurons modulate sensory-induced and stress-induced self-grooming via input-dependent mechanisms in mice

Self-grooming is an innate stereotyped behavior influenced by sense and emotion. It is considered an important characteristic in various disease models. However, the neural circuit mechanism underlying sensory-induced and emotion-driven self-grooming remains unclear. We found that the ventral zona incerta (Ziv) was activated during spontaneous self-grooming (SG), corn oil-induced sensory self-grooming (OG), and tail suspension-induced stress self-grooming (TG). Optogenetic excitation of Ziv parvalbumin (PV) neurons increased the duration of SG. Conversely, optogenetic inhibition of ZivPV neurons significantly reduced self-grooming in all three models. Furthermore, glutamatergic inputs from the primary sensory cortex activated the Ziv and contributed to OG. Activation of GABAergic inputs from the central amygdala to the Ziv increased SG, OG, and TG, potentially through local negative regulation of the Ziv. These findings suggest that the Ziv may play a crucial role in processing sensory and emotional information related to self-grooming, making it a potential target for regulating stereotyped behavior.

Neural substrates for regulating self-grooming behavior in rodents

Grooming, as an evolutionarily conserved repetitive behavior, is common in various animals, including humans, and serves essential functions including, but not limited to, hygiene maintenance, thermoregulation, de-arousal, stress reduction, and social behaviors. In rodents, grooming involves a patterned and sequenced structure, known as the syntactic chain with four phases that comprise repeated stereotyped movements happening in a cephalocaudal progression style, beginning from the nose to the face, to the head, and finally ending with body licking. The context-dependent occurrence of grooming behavior indicates its adaptive significance. This review briefly summarizes the neural substrates responsible for rodent grooming behavior and explores its relevance in rodent models of neuropsychiatric disorders and neurodegenerative diseases with aberrant grooming phenotypes. We further emphasize the utility of rodent grooming as a reliable measure of repetitive behavior in neuropsychiatric models, holding promise for translational psychiatry. Herein, we mainly focus on rodent self-grooming. Allogrooming (grooming being applied on one animal by its conspecifics via licking or carefully nibbling) and heterogrooming (a form of grooming behavior directing towards another animal, which occurs in other contexts, such as maternal, sexual, aggressive, or social behaviors) are not covered due to space constraints.

Loss of protein tyrosine phosphatase receptor delta PTPRD increases the number of cortical neurons, impairs synaptic function and induces autistic-like behaviors in adult mice

BACKGROUND

The brain cortex is responsible for many higher-level cognitive functions. Disruptions during cortical development have long-lasting consequences on brain function and are associated with the etiology of brain disorders. We previously found that the protein tyrosine phosphatase receptor delta Ptprd, which is genetically associated with several human neurodevelopmental disorders, is essential to cortical brain development. Loss of Ptprd expression induced an aberrant increase of excitatory neurons in embryonic and neonatal mice by hyper-activating the pro-neurogenic receptors TrkB and PDGFRβ in neural precursor cells. However, whether these alterations have long-lasting consequences in adulthood remains unknown.

RESULTS

Here, we found that in Ptprd+/- or Ptprd-/- mice, the developmental increase of excitatory neurons persists through adulthood, affecting excitatory synaptic function in the medial prefrontal cortex. Likewise, heterozygosity or homozygosity for Ptprd also induced an increase of inhibitory cortical GABAergic neurons and impaired inhibitory synaptic transmission. Lastly, Ptprd+/- or Ptprd-/- mice displayed autistic-like behaviors and no learning and memory impairments or anxiety.

CONCLUSIONS

These results indicate that loss of Ptprd has long-lasting effects on cortical neuron number and synaptic function that may aberrantly impact ASD-like behaviors.

Rats Lacking the Dopamine Transporter Display Inflexibility in Innate and Learned Behavior

Playing a key role in the organization of striatal motor output, the dopamine (DA)-ergic system regulates both innate and complex learned behaviors. Growing evidence clearly indicates the involvement of the DA-ergic system in different forms of repetitive (perseverative) behavior. Some of these behaviors accompany such disorders as obsessive-compulsive disorder (OCD), Tourette's syndrome, schizophrenia, and addiction. In this study, we have traced how the inflexibility of repetitive reactions in the recently developed animal model of hyper-DA-ergia, dopamine transporter knockout rats (DAT-KO rats), affects the realization of innate behavior (grooming) and the learning of spatial (learning and reversal learning in T-maze) and non-spatial (extinction of operant reaction) tasks. We found that the microstructure of grooming in DAT-KO rats significantly differed in comparison to control rats. DAT-KO rats more often demonstrated a fixed syntactic chain, making fewer errors and very rarely missing the chain steps in comparison to control rats. DAT-KO rats' behavior during inter-grooming intervals was completely different to the control animals. During learning and reversal learning in the T-maze, DAT-KO rats displayed pronounced patterns of hyperactivity and perseverative (stereotypical) activity, which led to worse learning and a worse performance of the task. Most of the DAT-KO rats could not properly learn the behavioral task in question. During re-learning, DAT-KO rats demonstrated rigid perseverative activity even in the absence of any reinforcement. In operant tasks, the mutant rats demonstrated poor extinction of operant lever pressing: they continued to perform lever presses despite no there being reinforcement. Our results suggest that abnormally elevated DA levels may be responsible for behavioral rigidity. It is conceivable that this phenomenon in DAT-KO rats reflects some of the behavioral traits observed in clinical conditions associated with endogenous or exogenous hyper-DA-ergia, such as schizophrenia, substance abuse, OCD, patients with Parkinson disease treated with DA mimetics, etc. Thus, DAT-KO rats may be a valuable behavioral model in the search for new pharmacological approaches to treat such illnesses.

Measuring the replicability of our own research

In the study of transgenic mouse models of neurodevelopmental and neurodegenerative disorders, we use batteries of tests to measure deficits in behaviour and from the results of these tests, we make inferences about the mental states of the mice that we interpret as deficits in "learning", "memory", "anxiety", "depression", etc. This paper discusses the problems of determining whether a particular transgenic mouse is a valid mouse model of disease X, the problem of background strains, and the question of whether our behavioural tests are measuring what we say they are. The problem of the reliability of results is then discussed: are they replicable between labs and can we replicate our results in our own lab? This involves the study of intra- and inter- experimenter reliability. The variables that influence replicability and the importance of conducting a complete behavioural phenotype: sensory, motor, cognitive and social emotional behaviour are discussed. Then the thorny question of failure to replicate is examined: Is it a curse or a blessing? Finally, the role of failure in research and what it tells us about our research paradigms is examined.

Hyperactivity of indirect pathway-projecting spiny projection neurons promotes compulsive behavior

Compulsive behaviors are a hallmark symptom of obsessive compulsive disorder (OCD). Striatal hyperactivity has been linked to compulsive behavior generation in correlative studies in humans and causal studies in rodents. However, the contribution of the two distinct striatal output populations to the generation and treatment of compulsive behavior is unknown. These populations of direct and indirect pathway-projecting spiny projection neurons (SPNs) have classically been thought to promote or suppress actions, respectively, leading to a long-held hypothesis that increased output of direct relative to indirect pathway promotes compulsive behavior. Contrary to this hypothesis, here we find that indirect pathway hyperactivity is associated with compulsive grooming in the Sapap3-knockout mouse model of OCD-relevant behavior. Furthermore, we show that suppression of indirect pathway activity using optogenetics or treatment with the first-line OCD pharmacotherapy fluoxetine is associated with reduced grooming in Sapap3-knockouts. Together, these findings highlight the striatal indirect pathway as a potential treatment target for compulsive behavior.

Age-related changes in species-typical behaviours in the 5xFAD mouse model of Alzheimer's disease from 4 to 16 months of age

Alzheimer's disease (AD) patients show age-related decreases in the ability to perform activities of daily living and the decline in these activities is related to the severity of neurobiological deterioration underlying the disease. The 5xFAD mouse model of AD shows age-related impairments in sensory- motor and cognitive function, but little is known about changes in species-typical behaviours that may model activities of daily living in AD patients. Therefore, we examined species-typical behaviours used as indices of exploration (rearing) and compulsivity (grooming) across six tests of anxiety-like behaviour or motor function in female 5xFAD mice from 3 to 16 months of age. Robust decreases in rearing were found in 5xFAD mice across all tests after 9 months of age, although few differences were observed in grooming. A fine-scale analysis of grooming, however, revealed a previously unresolved and spatially restricted pattern of grooming in 5xFAD mice at 13-16 months of age. We then examined changes in species-typical behaviours in the home-cage, and show impaired nest building in 5xFAD mice at all ages tested. Lastly, we examined the relationship between reduced species typical behaviours in 5xFAD mice and the presentation of freezing behaviour, a commonly used measure of memory for conditioned fear. These results showed that along with cognitive and sensory-motor behaviour, 5xFAD mice have robust age-related impairments in species-typical behaviours. Therefore, species typical behaviours in 5xFAD mice may help to model the decline in activities of daily living observed in AD patients, and may provide useful behavioural phenotypes for evaluating the pre-clinical efficacy of novel therapeutics for AD.

Amino acid formula induces microbiota dysbiosis and depressive-like behavior in mice

Amino acid formula (AAF) is increasingly consumed in infants with cow's milk protein allergy; however, the long-term influences on health are less described. In this study, we established a mouse model by subjecting neonatal mice to an amino acid diet (AAD) to mimic the feeding regimen of infants on AAF. Surprisingly, AAD-fed mice exhibited dysbiotic microbiota and increased neuronal activity in both the intestine and brain, as well as gastrointestinal peristalsis disorders and depressive-like behavior. Furthermore, fecal microbiota transplantation from AAD-fed mice or AAF-fed infants to recipient mice led to elevated neuronal activations and exacerbated depressive-like behaviors compared to that from normal chow-fed mice or cow's-milk-formula-fed infants, respectively. Our findings highlight the necessity to avoid the excessive use of AAF, which may influence the neuronal development and mental health of children.

A novel naïve Bayes approach to identifying grooming behaviors in the force-plate actometric platform

BACKGROUND

Self-grooming behavior in rodents serves as a valuable behavioral index for investigating stereotyped and perseverative responses. Most current grooming analyses rely on video observation, which lacks standardization, efficiency, and quantitative information about force. To address these limitations, we developed an automated paradigm to analyze grooming using a force-plate actometer.

NEW METHOD

Grooming behavior is quantified by calculating ratios of relevant movement power spectral bands. These ratios are input into a naïve Bayes classifier, trained with manual video observations. The effectiveness of this method was tested using CIN-d mice, an animal model developed through early-life depletion of striatal cholinergic interneurons (CIN-d) and featuring prolonged grooming responses to acute stressors. Behavioral monitoring was simultaneously conducted on the force-place actometer and by video recording.

RESULTS

The naïve Bayes approach achieved 93.7% accurate classification and an area under the receiver operating characteristic curve of 0.894. We confirmed that male CIN-d mice displayed significantly longer grooming durations than controls. However, this elevation was not correlated with increases in grooming force. Notably, the dopaminergic antagonist haloperidol reduced grooming force and duration.

COMPARISON WITH EXISTING METHODS

In contrast to observation-based approaches, our method affords rapid, unbiased, and automated assessment of grooming duration, frequency, and force.

CONCLUSIONS

Our novel approach enables fast and accurate automated detection of grooming behaviors. This method holds promise for high-throughput assessments of grooming stereotypies in animal models of neuropsychiatric disorders.

Intermittent Hypobaric Hypoxia Ameliorates Autistic-Like Phenotypes in Mice

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by persistent deficits in social communication and stereotyped behaviors. Although major advances in basic research on autism have been achieved in the past decade, and behavioral interventions can mitigate the difficulties that individuals with autism experience, little is known about the many fundamental issues of the interventions, and no specific medication has demonstrated efficiency for the core symptoms of ASD. Intermittent hypobaric hypoxia (IHH) is characterized by repeated exposure to lowered atmospheric pressure and oxygen levels, which triggers multiple physiological adaptations in the body. Here, using two mouse models of ASD, male Shank3B -/- and Fmr1 -/y mice, we found that IHH training at an altitude of 5,000 m for 4 h per day, for 14 consecutive days, ameliorated autistic-like behaviors. Moreover, IHH training enhanced hypoxia inducible factor (HIF) 1α in the dorsal raphe nucleus (DRN) and activated the DRN serotonergic neurons. Infusion of cobalt chloride into the DRN, to mimic IHH in increasing HIF1α expression or genetically knockdown PHD2 to upregulate HIF1α expression in the DRN serotonergic neurons, alleviated autistic-like behaviors in Shank3B -/- mice. In contrast, downregulation of HIF1α in DRN serotonergic neurons induced compulsive behaviors. Furthermore, upregulating HIF1α in DRN serotonergic neurons increased the firing rates of these neurons, whereas downregulation of HIF1α in DRN serotonergic neurons decreased their firing rates. These findings suggest that IHH activated DRN serotonergic neurons via upregulation of HIF1α, and thus ameliorated autistic-like phenotypes, providing a novel therapeutic option for ASD.

Role of the basal ganglia in innate and learned behavioural sequences

Integrating individual actions into coherent, organised behavioural units, a process called chunking, is a fundamental, evolutionarily conserved process that renders actions automatic. In vertebrates, evidence points to the basal ganglia - a complex network believed to be involved in action selection - as a key component of action sequence encoding, although the underlying mechanisms are only just beginning to be understood. Central pattern generators control many innate automatic behavioural sequences that form some of the most basic behaviours in an animal's repertoire, and in vertebrates, brainstem and spinal pattern generators are under the control of higher order structures such as the basal ganglia. Evidence suggests that the basal ganglia play a crucial role in the concatenation of simpler behaviours into more complex chunks, in the context of innate behavioural sequences such as chain grooming in rats, as well as sequences in which innate capabilities and learning interact such as birdsong, and sequences that are learned from scratch, such as lever press sequences in operant behaviour. It has been proposed that the role of the striatum, the largest input structure of the basal ganglia, might lie in selecting and allowing the relevant central pattern generators to gain access to the motor system in the correct order, while inhibiting other behaviours. As behaviours become more complex and flexible, the pattern generators seem to become more dependent on descending signals. Indeed, during learning, the striatum itself may adopt the functional characteristics of a higher order pattern generator, facilitated at the microcircuit level by striatal neuropeptides.

A comparison of machine learning methods for quantifying self-grooming behavior in mice

Background

As machine learning technology continues to advance and the need for standardized behavioral quantification grows, commercial and open-source automated behavioral analysis tools are gaining prominence in behavioral neuroscience. We present a comparative analysis of three behavioral analysis pipelines-DeepLabCut (DLC) and Simple Behavioral Analysis (SimBA), HomeCageScan (HCS), and manual scoring-in measuring repetitive self-grooming among mice.

Methods

Grooming behavior of mice was recorded at baseline and after water spray or restraint treatments. Videos were processed and analyzed in parallel using 3 methods (DLC/SimBA, HCS, and manual scoring), quantifying both total number of grooming bouts and total grooming duration.

Results

Both treatment conditions (water spray and restraint) resulted in significant elevation in both total grooming duration and number of grooming bouts. HCS measures of grooming duration were significantly elevated relative to those derived from manual scoring: specifically, HCS tended to overestimate duration at low levels of grooming. DLC/SimBA duration measurements were not significantly different than those derived from manual scoring. However, both SimBA and HCS measures of the number of grooming bouts were significantly different than those derived from manual scoring; the magnitude and direction of the difference depended on treatment condition.

Conclusion

DLC/SimBA provides a high-throughput pipeline for quantifying grooming duration that correlates well with manual scoring. However, grooming bout data derived from both DLC/SimBA and HCS did not reliably estimate measures obtained via manual scoring.

Reducing sugar intake through chronic swimming training: Exploring palatability changes and central vasopressin mechanisms

Excessive sugar intake has been associated with the onset of several non-communicable chronic diseases seen in humans. Physical activity could affect sweet taste perception which may affect sugar intake. Therefore, it was investigated the chronic effects of swimming training on sucrose intake/preference, reactivity to sucrose taste, self-care in neurobehavioral stress, and the possible involvement of the vasopressin type V1 receptor in sucrose solution intake. Male Wistar rats, of from different cohorts were used, subjected to a sedentary lifestyle (SED) or swimming training (TR - 1 h/day, 5×/week, for 8 weeks, with no added load). Weekly intake was verified in SED and TR rats after access to a sucrose solution 1×/week, 2 h/day, for eight weeks. Chronic effects of swimming and/or a sedentary lifestyle were carried out three days after the end of the physical exercise protocol. Swimming training reduced the intake of sucrose solution from the third week onwards in the two-bottle test measured once a week for 8 weeks. After the ending of the swimming protocol, sucrose intake was also reduced as per its preference. This reduced intake is probably correlated with the carbohydrate aspect of sucrose since saccharin intake was not affected. In addition, chronic swimming training was shown to reduce ingestive responses, increase neutral responses, without interfering with aversive, in the sucrose solution taste reactivity test. In addition, these results are not related to a depressive-like behavior, nor to neurobehavioral stress. Furthermore, treatment with vasopressin V1 receptor antagonist abolished the reduced sucrose intake in trained rats. The results suggest that swimming performed chronically is capable of reducing intake and preference for sucrose by decreasing the palatability of sucrose without causing depressive-type behavior or stress. In addition, the results also suggest that central V1 vasopressin receptors are part of the mechanisms activated to reduce sucrose intake in trained rats.

Prenatal allergic inflammation in rats confers sex-specific alterations to oxytocin and vasopressin innervation in social brain regions

Prenatal exposure to inflammation via maternal infection, allergy, or autoimmunity increases one's risk for developing neurodevelopmental and psychiatric disorders. Many of these disorders are associated with altered social behavior, yet the mechanisms underlying inflammation-induced social impairment remain unknown. We previously found that a rat model of acute allergic maternal immune activation (MIA) produced deficits like those found in MIA-linked disorders, including impairments in juvenile social play behavior. The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) regulate social behavior, including juvenile social play, across mammalian species. OT and AVP are also implicated in neuropsychiatric disorders characterized by social impairment, making them good candidate regulators of social deficits after MIA. We profiled how acute prenatal exposure to allergic MIA changed OT and AVP innervation in several brain regions important for social behavior in juvenile male and female rat offspring. We also assessed whether MIA altered additional behavioral phenotypes related to sociality and anxiety. We found that allergic MIA increased OT and AVP fiber immunoreactivity in the medial amygdala and had sex-specific effects in the nucleus accumbens, bed nucleus of the stria terminalis, and lateral hypothalamic area. We also found that MIA reduced ultrasonic vocalizations in neonates and increased the stereotypical nature of self-grooming behavior. Overall, these findings suggest that there may be sex-specific mechanisms underlying MIA-induced behavioral impairment and underscore OT and AVP as ideal candidates for future mechanistic studies.

The emerging complexity of molecular pathways implicated in mouse self-grooming behavior

Rodent self-grooming is an important complex behavior, and its deficits are translationally relevant to a wide range of neuropsychiatric disorders. Here, we analyzed a comprehensive dataset of 227 genes whose mutations are known to evoke aberrant self-grooming in mice. Using these genes, we constructed the network of their established protein-protein interactions (PPI), yielding several distinct molecular clusters related to postsynaptic density, the Wnt signaling, transcription factors, neuronal cell cycle, NOS neurotransmission, microtubule regulation, neuronal differentiation/trafficking, neurodevelopment and mitochondrial function. Utilizing further bioinformatics analyses, we also identified novel central ('hub') proteins within these clusters, whose genes may also be implicated in aberrant self-grooming and other repetitive behaviors in general. Untangling complex molecular pathways of this important behavior using in silico approaches contributes to our understanding of related neurological disorders, and may suggest novel potential targets for their pharmacological or gene therapy.

Combination Therapy with Platelet-Rich Plasma and Epidermal Neural Crest Stem Cells Increases Treatment Efficacy in Vascular Dementia

This study aimed to evaluate the efficacy and treatment mechanism of platelet-rich plasma (PRP) and neural crest-derived epidermal stem cells (ESCs) in their administration alone and combination in vascular dementia (VaD) model by two-vessel occlusion (2VO). Methods. Sixty-six rats were divided into six groups: the control, sham, 2VO + vehicle, 2VO + PRP, 2VO + ESC, and 2VO + ESC + PRP. The treated groups received 1 million cells on days 4, 14, and 21 with or without 500 µl PRP (twice a week) after 2VO. The memory performance and anxiety were evaluated by behavioral tests including open field, passive avoidance, and Morris water maze. The basal-synaptic transmission (BST) and long-term potentiation (LTP) were assessed through field-potential recordings of the CA1. The mRNA expression levels of IGF-1, TGF-β1, PSD-95, and GSk-3β were measured in the rat hippocampus by quantitative reverse transcription polymerase chain reaction. Results. The results demonstrated impaired learning, memory, and synaptic plasticity in the 2VO rats, along with a significant decrease in the expression of IGF-1, TGF-β1, PSD-95, and upregulation of GSK-3β. Treatment with ESC alone and ESC + PRP showed similar improvements in spatial memory and LTP induction, with associated upregulation of PSD-95 and downregulation of GSK-3β. However, only the ESC + PRP group showed recovery in BST. Furthermore, combination therapy was more effective than PRP monotherapy for LTP and memory. Conclusions. The transplantation of ESC showed better effects than PRP alone, and combination therapy increased the treatment efficacy with the recovery of BST. This finding may be a clue for the combination therapy of ESC and PRP for VaD.

Influence of the dose of ketamine used on schizophrenia-like symptoms in mice: A correlation study with TH, GAD67, and PPAR-γ

Schizophrenia is a chronic, debilitating mental illness that has not yet been completely understood. In this study, we aimed to investigate the effects of different doses of ketamine, a non-competitive NMDA receptor antagonist, on the positive- and negative-like symptoms of schizophrenia. We also explored whether these effects are related to changes in the immunoreactivity of GAD67, TH, and PPAR-γ in brain structures. To conduct the study, male mice received ketamine (20-40 mg/kg) or its vehicle (0.9 % NaCl) intraperitoneally for 14 consecutive days. We quantified stereotyped behavior, the time of immobility in the forced swimming test (FST), and locomotor activity after 7 or 14 days. In addition, we performed ex vivo analysis of the immunoreactivity of GAD, TH, and PPAR-γ, in brain tissues after 14 days. The results showed that ketamine administration for 14 days increased the grooming time in the nose region at all tested doses. It also increased immobility in the FST at 30 mg/kg doses and decreased the number of rearing cycles during stereotyped behavior at 40 mg/kg. These behavioral effects were not associated with changes in locomotor activity. We did not observe any significant alterations regarding the immunoreactivity of brain proteins. However, we found that GAD and TH were positively correlated with the number of rearing during the stereotyped behavior at doses of 20 and 30 mg/kg ketamine, respectively. GAD was positively correlated with the number of rearing in the open field test at a dose of 20 mg/kg. TH was inversely correlated with immobility time in the FST at a dose of 30 mg/kg. PPAR-γ was inversely correlated with the number of bouts of stereotyped behavior at a dose of 40 mg/kg of ketamine. In conclusion, the behavioral alterations induced by ketamine in positive-like symptoms were reproduced with all doses tested and appear to depend on the modulatory effects of TH, GAD, and PPAR-γ. Conversely, negative-like symptoms were associated with a specific dose of ketamine.

A subthalamo-parabrachial glutamatergic pathway is involved in stress-induced self-grooming in mice

Excessive self-grooming is an important behavioral phenotype of the stress response in rodents. Elucidating the neural circuit that regulates stress-induced self-grooming may suggest potential treatment to prevent maladaptation to stress that is implicated in emotional disorders. Stimulation of the subthalamic nucleus (STN) has been found to induce strong self-grooming. In this study we investigated the role of the STN and a related neural circuit in mouse stress-related self-grooming. Body-restraint and foot-shock stress-induced self-grooming models were established in mice. We showed that both body restraint and foot shock markedly increased the expression of c-Fos in neurons in the STN and lateral parabrachial nucleus (LPB). Consistent with this, the activity of STN neurons and LPB glutamatergic (Glu) neurons, as assessed with fiber photometry recording, was dramatically elevated during self-grooming in the stressed mice. Using whole-cell patch-clamp recordings in parasagittal brain slices, we identified a monosynaptic projection from STN neurons to LPB Glu neurons that regulates stress-induced self-grooming in mice. Enhanced self-grooming induced by optogenetic activation of the STN-LPB Glu pathway was attenuated by treatment with fluoxetine (18 mg·kg-1·d-1, p.o., for 2 weeks) or in the presence of a cage mate. Furthermore, optogenetic inhibition of the STN-LPB pathway attenuated stress-related but not natural self-grooming. Taken together, these results suggest that the STN-LPB pathway regulates the acute stress response and is a potential target for intervention in stress-related emotional disorders.

Minocycline improves autism-related behaviors by modulating microglia polarization in a mouse model of autism

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with few pharmacological treatments. Minocycline, a tetracycline derivative that inhibits microglial activation, has been well-identified with anti-inflammatory properties and neuroprotective effects. A growing body of research suggests that ASD is associated with neuroinflammation, abnormal neurotransmitter levels, and neurogenesis. Thus, we hypothesized that minocycline could improve autism-related behaviors by inhibiting microglia activation and altering neuroinflammation. To verify our hypothesis, we used a mouse model of autism, BTBR T + Itpr3tf/J (BTBR). As expected, minocycline administration rescued the sociability and repetitive, stereotyped behaviors of BTBR mice while having no effect in C57BL/6J mice. We also found that minocycline improved neurogenesis and inhibited microglia activation in the hippocampus of BTBR mice. In addition, minocycline treatment inhibited Erk1/2 phosphorylation in the hippocampus of BTBR mice. Our findings show that minocycline administration alleviates ASD-like behaviors in BTBR mice and improves neurogenesis, suggesting that minocycline supplementation might be a potential strategy for improving ASD symptoms.

Antioxidant Behavioural Phenotype in the Immp2l Gene Knock-Out Mouse

Mitochondrial dysfunction is strongly associated with autism spectrum disorder (ASD) and the Inner mitochondrial membrane protein 2-like (IMMP2L) gene is linked to autism inheritance. However, the biological basis of this linkage is unknown notwithstanding independent reports of oxidative stress in association with both IMMP2L and ASD. To better understand IMMP2L's association with behaviour, we developed the Immp2lKD knockout (KO) mouse model which is devoid of Immp2l peptidase activity. Immp2lKD -/- KO mice do not display any of the core behavioural symptoms of ASD, albeit homozygous Immp2lKD -/- KO mice do display increased auditory stimulus-driven instrumental behaviour and increased amphetamine-induced locomotion. Due to reports of increased ROS and oxidative stress phenotypes in an earlier truncated Immp2l mouse model resulting from an intragenic deletion within Immp2l, we tested whether high doses of the synthetic mitochondrial targeted antioxidant (MitoQ) could reverse or moderate the behavioural changes in Immp2lKD -/- KO mice. To our surprise, we observed that ROS levels were not increased but significantly lowered in our new Immp2lKD -/- KO mice and that these mice had no oxidative stress-associated phenotypes and were fully fertile with no age-related ataxia or neurodegeneration as ascertained using electron microscopy. Furthermore, the antioxidant MitoQ had no effect on the increased amphetamine-induced locomotion of these mice. Together, these findings indicate that the behavioural changes in Immp2lKD -/- KO mice are associated with an antioxidant-like phenotype with lowered and not increased levels of ROS and no oxidative stress-related phenotypes. This suggested that treatments with antioxidants are unlikely to be effective in treating behaviours directly resulting from the loss of Immp2l/IMMP2L activity, while any behavioural deficits that maybe associated with IMMP2L intragenic deletion-associated truncations have yet to be determined.

Increased NMDARs in neurons and glutamine synthetase in astrocytes underlying autistic-like behaviors of Gabrb1-/- mice

Mutations of the GABA-A receptor subunit β1 (GABRB1) gene are found in autism patients. However, it remains unclear how mutations in Gabrb1 may lead to autism. We generated Gabrb1-/- mouse model, which showed autistic-like behaviors. We carried out RNA-seq on the hippocampus and found glutamatergic pathway may be involved. We further carried out single-cell RNA sequencing on the whole brain followed by qRT-PCR, immunofluorescence, electrophysiology, and metabolite detection on specific cell types. We identified the up-regulated Glul/Slc38a3 in astrocytes, Grin1/Grin2b in neurons, glutamate, and the ratio of Glu/GABA in the hippocampus. Consistent with these results, increased NMDAR-currents and reduced GABAAR-currents in the CA1 neurons were detected in Gabrb1-/- mice. NMDAR antagonist memantine or Glul inhibitor methionine sulfoximine could rescue the abnormal behaviors in Gabrb1-/- mice. Our data reveal that upregulation of the glutamatergic synapse pathway, including NMDARs at neuronal synapses and glutamine exported by astrocytes, may lead to autistic-like behaviors.

Labeling PIEZO2 activity in the peripheral nervous system

Sensory neurons detect mechanical forces from both the environment and internal organs to regulate physiology. PIEZO2 is a mechanosensory ion channel critical for touch, proprioception, and bladder stretch sensation, yet its broad expression in sensory neurons suggests it has undiscovered physiological roles. To fully understand mechanosensory physiology, we must know where and when PIEZO2-expressing neurons detect force. The fluorescent styryl dye FM 1-43 was previously shown to label sensory neurons. Surprisingly, we find that the vast majority of FM 1-43 somatosensory neuron labeling in mice in vivo is dependent on PIEZO2 activity within the peripheral nerve endings. We illustrate the potential of FM 1-43 by using it to identify novel PIEZO2-expressing urethral neurons that are engaged by urination. These data reveal that FM 1-43 is a functional probe for mechanosensitivity via PIEZO2 activation in vivo and will facilitate the characterization of known and novel mechanosensory processes in multiple organ systems.

An allelic series of spontaneous Rorb mutant mice exhibit a gait phenotype, changes in retina morphology and behavior, and gene expression signatures associated with the unfolded protein response

The Retinoid-related orphan receptor beta (RORβ) gene encodes a developmental transcription factor and has 2 predominant isoforms created through alternative first exon usage; one specific to the retina and another present more broadly in the central nervous system, particularly regions involved in sensory processing. RORβ belongs to the nuclear receptor family and plays important roles in cell fate specification in the retina and cortical layer formation. In mice, loss of RORβ causes disorganized retina layers, postnatal degeneration, and production of immature cone photoreceptors. Hyperflexion or "high-stepping" of rear limbs caused by reduced presynaptic inhibition by Rorb-expressing inhibitory interneurons of the spinal cord is evident in RORβ-deficient mice. RORβ variants in patients are associated with susceptibility to various neurodevelopmental conditions, primarily generalized epilepsies, but including intellectual disability, bipolar, and autism spectrum disorders. The mechanisms by which RORβ variants confer susceptibility to these neurodevelopmental disorders are unknown but may involve aberrant neural circuit formation and hyperexcitability during development. Here we report an allelic series in 5 strains of spontaneous Rorb mutant mice with a high-stepping gait phenotype. We show retinal abnormalities in a subset of these mutants and demonstrate significant differences in various behavioral phenotypes related to cognition. Gene expression analyses in all 5 mutants reveal a shared over-representation of the unfolded protein response and pathways related to endoplasmic reticulum stress, suggesting a possible mechanism of susceptibility relevant to patients.

A novel naïve Bayes approach to identifying grooming behaviors in the force-plate actometric platform

Background

Self-grooming behavior in rodents serves as a valuable model for investigating stereotyped and perseverative responses. Most current grooming analyses primarily rely on video observation, which lacks standardization, efficiency, and quantitative information about force. To address these limitations, we developed an automated paradigm to analyze grooming using a force-plate actometer.

New Method

Grooming behavior is quantified by calculating ratios of relevant movement power spectral bands. These ratios are then input into a naïve Bayes classifier, trained with manual video observations. To validate the effectiveness of this method, we applied it to the behavioral analysis of the early-life striatal cholinergic interneuron depletion (CIN-d) mouse, a model of tic pathophysiology recently developed in our laboratory, which exhibits prolonged grooming responses to acute stressors. Behavioral monitoring was simultaneously conducted on the force-place actometer and by video recording.

Results

The naïve Bayes approach achieved 93.7% accurate classification and an area under the receiver operating characteristic curve of 0.894. We confirmed that male CIN-d mice displayed significantly longer grooming durations compared to controls. However, this elevation was not correlated with increases in grooming force. Notably, haloperidol, a benchmark therapy for tic disorders, reduced both grooming force and duration.

Comparison with Existing Methods

In contrast to observation-based approaches, our method affords rapid, unbiased, and automated assessment of grooming duration, frequency, and force.

Conclusions

Our novel approach enables fast and accurate automated detection of grooming behaviors. This method holds promise for high-throughput assessments of grooming stereotypies in animal models of tic disorders and other psychiatric conditions.

Alternative splicing and heparan sulfation converge on neurexin-1 to control glutamatergic transmission and autism-related behaviors

Neurexin synaptic organizing proteins are central to a genetic risk pathway in neuropsychiatric disorders. Neurexins also exemplify molecular diversity in the brain, with over a thousand alternatively spliced forms and further structural heterogeneity contributed by heparan sulfate glycan modification. Yet, interactions between these modes of post-transcriptional and post-translational modification have not been studied. We reveal that these regulatory modes converge on neurexin-1 splice site 5 (S5): the S5 insert increases the number of heparan sulfate chains. This is associated with reduced neurexin-1 protein level and reduced glutamatergic neurotransmitter release. Exclusion of neurexin-1 S5 in mice boosts neurotransmission without altering the AMPA/NMDA ratio and shifts communication and repetitive behavior away from phenotypes associated with autism spectrum disorders. Thus, neurexin-1 S5 acts as a synaptic rheostat to impact behavior through the intersection of RNA processing and glycobiology. These findings position NRXN1 S5 as a potential therapeutic target to restore function in neuropsychiatric disorders.

Lateral septum as a melanocortin downstream site in obesity development

The melanocortin pathway is well established to be critical for body-weight regulation in both rodents and humans. Despite extensive studies focusing on this pathway, the downstream brain sites that mediate its action are not clear. Here, we found that, among the known paraventricular hypothalamic (PVH) neuron groups, those expressing melanocortin receptors 4 (PVH^Mc4R) preferably project to the ventral part of the lateral septum (LSv), a brain region known to be involved in emotional behaviors. Photostimulation of PVH^Mc4R neuron terminals in the LSv reduces feeding and causes aversion, whereas deletion of Mc4Rs or disruption of glutamate release from LSv-projecting PVH neurons causes obesity. In addition, disruption of AMPA receptor function in PVH-projected LSv neurons causes obesity. Importantly, chronic inhibition of PVH- or PVH^Mc4R-projected LSv neurons causes obesity associated with reduced energy expenditure. Thus, the LSv functions as an important node in mediating melanocortin action on body-weight regulation.

Chronic intermittent ethanol exposure disrupts stress-related tripartite communication to impact affect-related behavioral selection in male rats

Alcohol use disorder (AUD) is characterized by loss of intake control, increased anxiety, and susceptibility to relapse inducing stressors. Both astrocytes and neurons contribute to behavioral and hormonal consequences of chronic intermittent ethanol (CIE) exposure in animal models. Details on how CIE disrupts hypothalamic neuro-glial communication, which mediates stress responses are lacking. We conducted a behavioral battery (grooming, open field, reactivity to a single, uncued foot-shock, intermittent-access two-bottle choice ethanol drinking) followed by Ca²⁺ imaging in ex-vivo slices of paraventricular nucleus of the hypothalamus (PVN) from male rats exposed to CIE vapor or air-exposed controls. Ca²⁺ signals were evaluated in response to norepinephrine (NE) with or without selective α-adrenergic receptor (αAR) or GluN2B-containing N-methyl-D-aspartate receptor (NMDAR) antagonists, followed by dexamethasone (DEX) to mock a pharmacological stress response. Expectedly, CIE rats had altered anxiety-like, rearing, grooming, and drinking behaviors. Importantly, NE-mediated reductions in Ca²⁺ event frequency were blunted in both CIE neurons and astrocytes. Administration of the selective α1AR antagonist, prazosin, reversed this CIE-induced dysfunction in both cell types. Additionally, the pharmacological stress protocol reversed the altered basal Ca²⁺ signaling profile of CIE astrocytes. Signaling changes in astrocytes in response to NE were correlated with anxiety-like behaviors, such as the grooming:rearing ratio, suggesting tripartite synaptic function plays a role in switching between exploratory and stress-coping behavior. These data show how CIE exposure causes persistent changes to PVN neuro-glial function and provides the groundwork for how these physiological changes manifest in behavioral selection.

Progressive tremor and motor impairment in seizure-prone mutant tremor mice are associated with neurotransmitter dysfunction

BACKGROUND

The tremor mutant mice present motor impairments comprised of whole-body tremors, ataxia, decreased exploratory behavior, and audiogenic seizures.

OBJECTIVES

This study aims to investigate the development of motor dysfunction in this mutant mouse and the relationships with cortical, striatal, and cerebellar levels of GABA, glutamate, glycine, dopamine (DA), serotonin (5-HT), noradrenaline (NOR), and its metabolites. The serum cytokines levels, myelin content, and the astrocytic expression of the glial fibrillary acidic protein (GFAP) investigated the possible influence of inflammation in motor dysfunction.

RESULTS

Relative to wild-type (WT) mice, the tremor mice presented: increased tremors and bradykinesia associated with postural instability, decreased range of motion, and difficulty in initiating voluntary movements directly proportional to age; reduced step length for right and left hindlimbs; reduced cortical GABA, glutamate and, aspartate levels, the DOPAC/DA and ratio and increased the NOR levels; in the striatum, the levels of glycine and aspartate were reduced while the HVA levels, the HVA/DA and 5HIAA/5-HT ratios increased; in the cerebellum the glycine, NOR and 5-HIAA levels increased.

CONCLUSIONS

We suggest that the motor disturbances resulted mainly from the activation of the indirect striatal inhibitory pathway to the frontal cortex mediated by GABA, glutamate, and aspartate, reducing the dopaminergic activity at the prefrontal cortex, which was associated with the progressive tremor. The reduced striatal and increased cerebellar glycine levels could be partially responsible for the mutant tremor motor disturbances.

Effects of water restriction and dirt on grooming behavior in neotropical rodents (Trinomys setosus and T. yonenagae) (Echimyidae)

Grooming in rodents presents an evolutionarily conserved behavioral pattern that may cause water loss since saliva is deposited during washing onto large body surfaces. Trinomys yonenagae and Trinomys setosus are sister species of spiny rats occurring in Brazil, the former inhabiting a paleodesert of fixed dunes in the Caatinga, the latter being found in mesic environments of the Atlantic Forest. Consequently, it is expected that both species evolved under different selective pressures related to water balance, with T. yonenagae presenting mechanisms for dealing with water deprivation not found in T. setosus. Reduction of self-cleaning expression seems to offer a possible way to save water, as previously suggested by studies of the sand-dwelling spiny rat. Therefore, we propose to investigate grooming under four conditions: 'control' (C), a regimen of 'water restriction' (WR), of 'dirt' (D), and the combination of both conflicting stimuli (WR + D), in T. setosus, T. yonenagae, and Rattus norvegicus to compare the behavioral responses of these species. The main differences are observed in the forest dweller: T. setosus expresses a low relative duration of face washing under C, whose value is intermediate between the ones found in the two other species. WR treatment does not alter this pattern, however, the addition of dirt (D, WR + D) significantly increases the relative duration of washing in relation to C. Locomotor activity is decreased both in T. setosus and Wistar rats when they are under WR, a situation that could jeopardize antipredatory performance. T. yonenagae, the sand dweller, maintains a significantly lower expression of washing under C, as previously suggested, and under WR, D and WR + D. In addition, differently from the other two species the sand dweller maintains a normal activity level during all treatments. This study suggests differences in grooming as a strategy alluding to water balance by the two spiny rats inhabiting different ecosystems. A significantly clear pattern that saves water is observed in T. yonenagae, which probably has contributed to his evolution in one of the hottest semiarid areas of the world.

Excitatory SST neurons in the medial paralemniscal nucleus control repetitive self-grooming and encode reward

The use of body-focused repetitive behaviors (BFRBs) is conceptualized as a means of coping with stress. However, the neurological mechanism by which repetitive behaviors affect anxiety regulation is unclear. Here, we identify that the excitatory somatostatin-positive neurons in the medial paralemniscal nucleus (MPL^SST neurons) in mice promote self-grooming and encode reward. MPL^SST neurons display prominent grooming-related neuronal activity. Loss of function of MPL^SST neurons impairs both self-grooming and post-stress anxiety alleviation. Activation of MPL^SST neurons is rewarding and sufficient to drive reinforcement by activating dopamine (DA) neurons in the ventral tegmental area (VTA) and eliciting dopamine release. The neuropeptide SST facilitates the rewarding impact of MPL^SST neurons. MPL^SST neuron-mediated self-grooming is triggered by the input from the central amygdala (CeA). Our study reveals a dual role of CeA-MPL^SST-VTA^DA circuit in self-grooming and post-stress anxiety regulation and conceptualizes MPL^SST neurons as an interface linking the stress and reward systems in mice.

Differential effects of levetiracetam on hippocampal CA1 synaptic plasticity and molecular changes in the dentate gyrus in epileptic rats

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsies. Pharmacological treatment with anti-seizure drugs (ASDs) remains the mainstay in epilepsy management. Levetiracetam (LEV) is a second-generation ASD with a novel SV2A protein target and is indicated for treating focal epilepsies. While there is considerable literature in acute models, its effect in chronic epilepsy is less clear. Particularly, its effects on neuronal excitability, synaptic plasticity, adult hippocampal neurogenesis, and histological changes in chronic epilepsy have not been evaluated thus far, which formed the basis of the present study. Six weeks post-lithium-pilocarpine-induced status epilepticus (SE), epileptic rats were injected with levetiracetam (54mg/kg b.w. i.p.) once daily for two weeks. Following LEV treatment, Schaffer collateral - CA1 (CA3-CA1) synaptic plasticity and structural changes in hippocampal subregions CA3 and CA1 were evaluated. The number of doublecortin (DCX⁺) and reelin (RLN⁺) positive neurons was estimated. Further, mossy fiber sprouting was evaluated in DG by Timm staining, and splash test was performed to assess the anxiety-like behavior. Chronic epilepsy resulted in decreased basal synaptic transmission and increased paired-pulse facilitation without affecting post-tetanic potentiation and long-term potentiation. Moreover, chronic epilepsy decreased hippocampal subfields volume, adult hippocampal neurogenesis, and increased reelin expression and mossy fiber sprouting with increased anxiety-like behavior. LEV treatment restored basal synaptic transmission and paired-pulse facilitation ratio in CA3-CA1 synapses. LEV also restored the CA1 subfield volume in chronic epilepsy. LEV did not affect epilepsy-induced abnormal adult hippocampal neurogenesis, ectopic migration of newborn granule cells, mossy fiber sprouting in DG, and anxiety-like behavior. Our results indicate that in addition to reducing seizures, LEV has favorable effects on synaptic transmission and structural plasticity in chronic epilepsy. These findings add new dimensions to the use of LEV in chronic epilepsy and paves way for further research into its effects on cognition and affective behavior.

Self-directed orofacial grooming promotes social attraction in mice via chemosensory communication

Self-grooming is a stereotyped behavior displayed by nearly all animals. Among other established functions, self-grooming is implicated in social communication. However, whether self-grooming specifically influences behaviors of nearby individuals has not been directly tested, partly because of the technical challenge of inducing self-grooming in a reliable and temporally controllable manner. We recently found that optogenetic activation of dopamine D3 receptor expressing neurons in the ventral striatal islands of Calleja robustly induces orofacial grooming in mice. Using this optogenetic manipulation, here we demonstrate that observer mice exhibit social preference for mice that groom more regardless of biological sex. Moreover, grooming-induced social attraction depends on volatile chemosensory cues broadcasted from grooming mice. Collectively, our study establishes self-grooming as a means of promoting social attraction among mice via volatile cues, suggesting an additional benefit for animals to allocate a significant amount of time to this behavior.

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An optogenetic approach induces orofacial grooming with temporal precision in mice

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Observer mice show social preference toward mice that groom more regardless of sex

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Preference toward grooming mice requires main olfactory epithelia of observer mice

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Grooming-induced attraction depends on orofacial secretions from grooming mice

Prophylactic efficacy of ketamine, but not the low-trapping NMDA receptor antagonist AZD6765, against stress-induced maladaptive behavior and 4E-BP1-related synaptic protein synthesis impairment

Ketamine enhances the resilience against stress-induced depressive-like behavior, but its prophylactic efficacy in anxiety-related behaviors remains to be elucidated. Moreover, there is a need for developing novel preventive strategies against depressive- and anxiety-like behavior. AZD6765, a low-trapping NMDA receptor antagonist, shares with ketamine common molecular targets and produces rapid-onset antidepressant effects, suggesting that it could be a prophylactic agent. Therefore, this study investigated the prophylactic effect of ketamine against the depressive- and anxiety-like behavior induced by chronic restraint stress (2 h/day, for 10 days) in mice. We also investigated if AZD6765 exerts a resilience-enhancing response against these maladaptive behaviors. The contribution of 4E-BP1-related synaptic proteins synthesis (PSD-95/GluA1) in the possible pro-resilience efficacy of ketamine and AZD6765 was investigated. A single administration of ketamine (5 mg/kg, i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.), given 1 week before the stress protocol, was effective in preventing stress-induced depressive-like behavior in the tail suspension test and splash test. Ketamine administered at 1 and 5 mg/kg (i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.), prevented stress-induced anxiety-related self-grooming alterations. Stress-induced reduction on 4E-BP1 phosphorylation and PSD-95 and GluA1 immunocontent in the prefrontal cortex was prevented by ketamine (5 mg/kg, i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.). The results indicate that ketamine, but not AZD6765, exerts a pro-resilience response against stress-induced maladaptive behavior, reinforcing that it could be a prophylactic agent to manage individuals at-risk to develop MDD and anxiety.

A dystonia mouse model with motor and sequencing deficits paralleling human disease

The dystonias are a group of movement disorders characterized by involuntary twisting movements and postures. A lack of well characterized behavioral models of dystonia has impeded identification of circuit abnormalities giving rise to the disease. Most mouse behavioral assays are implemented independently of cortex, but cortical dysfunction is implicated in human dystonia. It is therefore important to identify dystonia models in which motor cortex-dependent behaviors are altered in ways relevant to human disease. The goal of this study was to characterize a cortically-dependent behavior in the recently-developed Dlx-CKO mouse model of DYT1 dystonia. Mice performed two tasks: skilled reaching and water-elicited grooming. These tests assess motor learning, dexterous skill, and innate motor sequencing. Furthermore, skilled reaching depends strongly on motor cortex, while dorsal striatum is critical for normal grooming. Dlx-CKO mice exhibited significantly lower success rates and pellet contacts compared to control mice during skilled reaching. Despite the skilled reaching impairments, Dlx-CKO mice adapt their reaching strategies. With training, they more consistently contacted the target. Grooming patterns of Dlx-CKO mice are more disorganized than in control mice, as evidenced by a higher proportion of non-chain grooming. However, when Dlx-CKO mice engage in syntactic chains, they execute them similarly to control mice. These abnormalities may provide targets for preclinical intervention trials, as well as facilitate determination of the physiologic path from torsinA dysfunction to motor phenotype.