Neonatal immune stimulation results in sex-specific changes in ultrasonic vocalizations but does not affect seizure susceptibility in neonatal mice

Neuroinflammation during the neonatal period has been linked to disorders such as autism and epilepsy. In this study, we investigated the early life behavioral consequences of a single injection of lipopolysaccharide (LPS) at postnatal day 10 (PD10) in mice. To assess deficits in communication, we performed the isolation-induced ultrasonic vocalizations (USVs) test at PD12. To determine if early life immune stimulus could alter seizure susceptibility, latency to flurothyl-induced generalized seizures was measured at 4 hours (hrs), 2 days, or 5 days after LPS injections. LPS had a sex-dependent effect on USV number. LPS-treated male mice presented significantly fewer USVs than LPS-treated female mice. However, the number of calls did not significantly differ between control and LPS for either sex. In male mice, we found that downward, short, and composite calls were significantly more prevalent in the LPS treatment group, while upward, chevron, and complex calls were less prevalent than in controls (p < 0.05). Female mice that received LPS presented a significantly higher proportion of short, frequency steps, two-syllable, and composite calls in their repertoire when compared with female control mice (p < 0.05). Seizure latency was not altered by early-life inflammation at any of the time points measured. Our findings suggest that early-life immune stimulation at PD10 disrupts vocal development but does not alter the susceptibility to flurothyl-induced seizures during the neonatal period. Additionally, the effect of inflammation in the disruption of vocalization is sex-dependent.

Neuronal deletion of phosphatase and tensin homolog in mice results in spatial dysregulation of adult hippocampal neurogenesis

Adult neurogenesis is a persistent phenomenon in mammals that occurs in select brain structures in both healthy and diseased brains. The tumor suppressor gene, phosphatase and tensin homolog deleted on chromosome 10 (Pten) has previously been found to restrict the proliferation of neural stem/progenitor cells (NSPCs) in vivo. In this study, we aimed to provide a comprehensive picture of how conditional deletion of Pten may regulate the genesis of adult NSPCs in the dentate gyrus of the hippocampus and the subventricular zone bordering the lateral ventricles. Using conventional markers and stereology, we quantified multiple stages of neurogenesis, including proliferating cells, immature neurons (neuroblasts), and apoptotic cells in several regions of the dentate gyrus, including the subgranular zone (SGZ), outer granule cell layer (oGCL), molecular layer, and hilus at 4 and 10 weeks of age. Our data demonstrate that conditional deletion of Pten in mice produces successive increases in dentate gyrus proliferating cells and immature neuroblasts, which confirms the known negative roles Pten has on cell proliferation and maturation. Specifically, we observe a significant increase in Ki67+ proliferating cells in the neurogenic SGZ at 4 weeks of age, but not 10 weeks of age. We also observe a delayed increase in neuroblasts at 10 weeks of age. However, our study expands on previous work by providing temporal, subregional, and neurogenesis-stage resolution. Specifically, we found that Pten deletion initially increases cell proliferation in the neurogenic SGZ, but this increase spreads to non-neurogenic dentate gyrus areas, including the hilus, oGCL, and molecular layer, as mice age. We also observed region-specific increases in apoptotic cells in the dentate gyrus hilar region that paralleled the regional increases in Ki67+ cells. Our work is accordant with the literature showing that Pten serves as a negative regulator of dentate gyrus neurogenesis but adds temporal and spatial components to the existing knowledge.

Hippocampal Upregulation of Complement Component C3 in Response to Lipopolysaccharide Stimuli in a Model of Fragile-X Syndrome

The complement system is part of the innate immune system and has been shown to be altered in autism spectrum disorder (ASD). Fragile-X syndrome (FXS) is the main genetic cause of ASD and studies suggest a dysregulation in the immune system in patients with the disorder. To assess if an animal model of FXS presents with altered complement signaling, we treated male Fmr1 knockout (KO) mice with lipopolysaccharide (LPS) and collected the hippocampus 24 h later. Assessment of the expression of the complement genes C1q, C3, and C4 identified the upregulation of C3 in both wild-type (WT) and knockout mice. Levels of C3 also increased in both genotypes. Analysis of the correlation between the expression of C3 and the cytokines IL-6, IL-1β, and TNF-α identified a different relationship between the expression of the genes in Fmr1 KO when compared to WT mice. Our findings did not support our initial hypotheses that the lack of the FMR1 gene would alter complement system signaling, and that the induction of the complement system in response to LPS in Fmr1 KO mice differed from wild-type conspecifics.

Neocortical and cerebellar malformations affect flurothyl-induced seizures in female C57BL/6J mice

Brain malformations cause cognitive disability and seizures in both human and animal models. Highly laminated structures such as the neocortex and cerebellum are vulnerable to malformation, affecting lamination and neuronal connectivity as well as causing heterotopia. The objective of the present study was to determine if sporadic neocortical and/or cerebellar malformations in C57BL/6J mice are correlated with reduced seizure threshold. The inhaled chemi-convulsant flurothyl was used to induce generalized, tonic-clonic seizures in male and female C57BL/6J mice, and the time to seizure onset was recorded as a functional correlate of brain excitability changes. Following seizures, mice were euthanized, and brains were extracted for histology. Cryosections of the neocortex and cerebellar vermis were stained and examined for the presence of molecular layer heterotopia as previously described in C57BL/6J mice. Over 60% of mice had neocortical and/or cerebellar heterotopia. No sex differences were observed in the prevalence of malformations. Significantly reduced seizure onset time was observed dependent on sex and the type of malformation present. These results raise important questions regarding the presence of malformations in C57BL/6J mice used in the study of brain development, epilepsy, and many other diseases of the nervous system.

Lipopolysaccharide-induced sickness behavior is not altered in male Fmr1-deficient mice

OBJECTIVES

Fragile X syndrome is the main monogenetic cause of intellectual disability and autism. Alterations in the immune system are commonly found in these developmental disorders. We and others have demonstrated that Fmr1 mutant mice present an altered response to immune stimuli. However, whether this altered immune response can influence the Fmr1 mutant behavioral outcomes in response to inflammation has not been fully investigated.

MATERIALS AND METHODS

In the current study, we examine the behavioral sickness response of male wildtype and knockout  mice to the innate immune stimulus lipopolysaccharide (LPS) (0.1 mg/kg) to determine if Fmr1 mutants have altered sickness behavior. We used an enzyme-linked immunosorbent assay (ELISA) to measure changes in the cytokine interleukin-6 (IL-6) to determine that inflammation was induced in the mice. Sickness behavior was assessed in a wheel-running paradigm, and a tail suspension test was used to assess the depressive-like phenotype that follows sickness behavior in response to LPS.

RESULTS

The ELISA using blood serum confirmed a significant increase in IL-6 in mice that were treated with LPS. Treated Fmr1 mutants exhibited decreased distance traveled in the wheel running after LPS administration, similar to treated controls. Another cohort of animals treated with LPS were tested in the tail suspension test and exhibited no alterations in immobility time in response to LPS.

CONCLUSION

Together, our data suggest that Fmr1 mutant mice do not have altered sickness behavior in response to a low dose of LPS.

Rapamycin improves social and stereotypic behavior abnormalities induced by pre-mitotic neuronal subset specific Pten deletion

The mechanistic target of rapamycin (mTOR) pathway is a signaling system integral to neural growth and migration. In both patients and rodent models, mutations to the phosphatase and tensin homolog gene (PTEN) on chromosome 10 results in hyperactivation of the mTOR pathway, as well as seizures, intellectual disabilities and autistic behaviors. Rapamycin, an inhibitor of mTOR, can reverse the epileptic phenotype of neural subset specific Pten knockout (NS-Pten KO) mice, but its impact on behavior is not known. To determine the behavioral effects of rapamycin, male and female NS-Pten KO and wildtype (WT) mice were assigned as controls or administered 10 mg/kg of rapamycin for 2 weeks followed by behavioral testing. Rapamycin improved social behavior in both genotypes and stereotypic behaviors in NS-Pten KO mice. Rapamycin treatment resulted in a reduction of several measures of activity in the open field test in both genotypes. Rapamycin did not reverse the reduced anxiety behavior in KO mice. These data show the potential clinical use of mTOR inhibitors by showing its administration can reduce the production of autistic-like behaviors in NS-Pten KO mice.

Vitamin D supplementation positively affects activity but impairs stimulus response behavior in an age and sex specific manner in C57BL/6 mice

Several studies have begun to demonstrate the possible cognitive and physiological benefits of a fortified vitamin D diet. However, the behavioral effects of a high vitamin D fortified diet during adolescence has not been fully explored. In the present study, a 4-week vitamin D fortified diet (20,000 IU/Kg) compared to controls (1500 IU/Kg) was administered during the juvenile (4 weeks old) or early adult period (8 weeks old) in C57BL/6 J mice to investigate the effects of fortification on cognition, behavior, and their bone phenotype. After 4 weeks on the diet, vitamin D-treated and control groups underwent a 4-week battery of behavioral tests while remaining on their respective diets. We found that a fortified diet affected behavior in both an age- and sex-specific manner. When vitamin D was administered to juveniles, both sexes displayed impaired habituation to a loud tone. However, females also presented with impaired prepulse inhibition compared to female controls. In the adult treated group, the fortified diet increased only time spent in the open field and had no effect on anxiety-like behavior in the elevated plus maze. Juvenile mice treated with a high vitamin D fortified diet showed a decrease in the total volume compared to the control group in the proximal metaphysis and midshaft region of their femur. There were no differences in bone measurements for mice treated during adulthood. Overall, our results suggest that the juvenile period is a more sensitive time point to the startle response and bone effects of a diet supplemented with high vitamin D, while adults exhibited alterations in locomotive behavior.

Assessment of tau phosphorylation and β-amyloid pathology in human drug-resistant epilepsy

OBJECTIVE

Epilepsy can be comorbid with cognitive impairments. Recent evidence suggests the possibility that cognitive decline in epilepsy may be associated with mechanisms typical of Alzheimer's disease (AD). Neuropathological hallmarks of AD have been found in brain biopsies surgically resected from patients with drug-resistant epilepsies. These include hyperphosphorylation of the tau protein (p-tau) that aggregate into neuropil threads (NT) or neurofibrillary tangles (NFT), as well as presence of β-amyloid (Aβ) deposits. While recent studies agree on these AD neuropathological findings in epilepsy, some contrast in their correlation to cognitive decline. Thus, to further address this question we determined the abundance of p-tau and Aβ proteins along with their association to cognitive function in 12 cases of refractory epilepsy.

METHODS

Cortical biopsies surgically extracted from the temporal lobes of patients with refractory epilepsy were processed for immunohistology and enzyme-linked immunoassays to assess distribution and levels, respectively, of p-tau (Antibodies: Ser202/Thr205; Thr205; Thr181) and Aβ proteins. In parallel, we measured activation of mechanistic target of rapamycin (mTOR) via p-S6 (Antibodies: Ser240/244; Ser235/236). Pearson correlation coefficient analysis determined associations between these proteins and neurophysiological scores for full scale intelligence quotient (FSIQ).

RESULTS

We found a robust presence of p-tau (Ser202/Thr205)-related NT and NFT pathology, as well as Aβ deposits, and p-S6 (Ser240/244; Ser235/236) in the epilepsy biopsies. We found no significant correlations between FSIQ and p-tau (Thr205; Thr181), Aβ or mTOR markers with FSIQ scores, although some correlation coefficients were modest to strong.

SIGNIFICANCE

These findings strongly support the existence of hyperphosphorylated tau protein and Aβ deposits in patients with human refractory epilepsy. However, their relation to cognitive decline is still unclear and requires further investigation.

Assessment of the effects of sex, age, and rearing condition on ultrasonic vocalizations elicited by pups during the maternal potentiation paradigm in C57BL/6J mice

Isolation-induced ultrasonic vocalizations (USVs) are important to elicit parental retrieval. This behavior is critical for the animal's survival and can be altered in models of developmental disorders. The potentiation of vocalizations in response to reunion with the dam, also called maternal potentiation, has been extensively studied in rats. However, the assessment of this paradigm in mice is scarce. In rats, the potentiation of vocalizations is dependent on rearing conditions. Since mice are the main species used for genetic models of diseases, we aimed to investigate how different factors such as age, sex, and rearing conditions can affect the potentiation of vocalizations in the maternal potentiation paradigm in mice. We carried out experiments using biparental (dam and sire) or uniparental rearing (dam). Pups were tested on postnatal days (PD) 9 or 12. Pups showed increased potentiation in both sexes at PD9 with uniparental rearing. Both rearing conditions and ages changed the repertoire from the first to the second isolation. Spectral parameters were affected by sex, rearing condition and reunion at PD9. At PD12, only duration was altered by reunion. We conclude that the performance of the pups in the maternal potentiation paradigm is dependent on age, sex, and rearing condition.

Neuronal subset-specific phosphatase and tensin homolog knockout mice exhibit age and brain region-associated alterations in microglia/macrophage activation

Seizures induce brain region-dependent enhancements in microglia/macrophage activation. Neuronal subset-specific phosphatase and tensin homolog (PTEN) knockout (KO) mice display hyperactive mammalian target of rapamycin (mTOR) signaling in the hippocampus, cerebellum, and cortex followed by seizures that increase in severity with age. To determine if KO mice also exhibit alterations in the spatiotemporal activation pattern of microglia, we used flow cytometry to compare the percentage of major histocompatibility complex-II activated microglia/macrophages between KO and wildtype (WT) mice at 5, 10, and 15 weeks of age. At 5 weeks, microglia/macrophage activation was greater in the cortex, P < 0.001, cerebellum, P < 0.001, and hippocampus, P < 0.001, of KO compared to WT mice. At 10 weeks, activation was greatest in the cortex of KO mice, P < 0.001, in the cerebellum of WT mice, P < 0.001, but similar in the hippocampus, P > 0.05. By 15 weeks, activation in the hippocampus was more than 25 times greater in KO mice compared to WT mice, P < 0.001. We show that hyperactive mTOR signaling is associated with an altered spatiotemporal pattern of microglia/macrophage activation in the brain and induces an enhanced neuroimmune response in the hippocampus.

Dietary rescue of adult behavioral deficits in the Fmr1 knockout mouse

The current study aimed to further address important questions regarding the therapeutic efficacy of omega-3 fatty acids for various behavioral and neuroimmune aspects of the Fmr1 phenotype. To address these questions, our experimental design utilized two different omega-3 fatty acid administration timepoints, compared to both standard laboratory chow controls ("Standard") and a diet controlling for the increase in fat content ("Control Fat"). In the first paradigm, post-weaning supplementation (after postnatal day 21) with the omega-3 fatty acid diet ("Omega-3") reversed deficits in startle threshold, but not deficits in prepulse inhibition, and the effect on startle threshold was not specific to the Omega-3 diet. However, post-weaning supplementation with both experimental diets also impaired acquisition of a fear response, recall of the fear memory and contextual fear conditioning compared to the Standard diet. The post-weaning Omega-3 diet reduced hippocampal expression of IL-6 and this reduction of IL-6 was significantly associated with diminished performance in the fear conditioning task. In the perinatal experimental paradigm, the Omega-3 diet attenuated hyperactivity and acquisition of a fear response. Additionally, perinatal exposure to the Control Fat diet (similar to a "Western" diet) further diminished nonsocial anxiety in the Fmr1 knockout. This study provides significant evidence that dietary fatty acids throughout the lifespan can significantly impact the behavioral and neuroimmune phenotype of the Fmr1 knockout model.

Multiple Early-Life Seizures Alters Neonatal Communicative Behavior in Fmr1 Knockout Mice

Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and a significant contributor to Autism Spectrum Disorder. Individuals with FXS are subject to developing numerous comorbidities, one of the most prevalent being seizures. In the present study, we investigated how seizures affected neonatal communicative behavior in the FXS mouse model. On postnatal day (PD) 7 through 11, we administered 3 flurothyl seizures per day to both Fmr1 knockout and wild-type C57BL/6J male mice. Ultrasonic vocalizations were recorded on PD12. Statistically significant alterations were found in both spectral and temporal measurements across seizure groups. We found that induction of seizures across PD7-11 resulted in an increased fundamental frequency (pitch) of ultrasonic vocalizations produced (p < 0.05), a longer duration of calls (p < 0.05), and a greater cumulative duration of calls (p < 0.05) in both genotypes. Induction of seizures across PD7-11 also resulted in a decreased latency to the first emitted vocalization (p < 0.05) and a decrease in mean power (loudness) for their vocalizations (p < 0.05). Early-life seizures also resulted in an increase in the number of downward and frequency step call types (p < 0.05). There was a significant increase in the number of chevron calls emitted from the Fmr1 knockout mice that received seizures compared to knockout control and wild-type seizure mice (p < 0.05). Overall, this study provides evidence that early-life seizures result in communication impairments and that superimposing seizures in Fmr1 knockout mice does produce an additional deficit in vocalization.

A comparison of four commercially available RNA extraction kits for wastewater surveillance of SARS-CoV-2 in a college population

Localized wastewater surveillance has allowed for public health officials to gain a broader understanding of SARS-CoV-2 viral prevalence in the community allowing public health officials time to prepare for impending outbreaks. Given variable levels of virus in the population through public health interventions, proper concentration and extraction of viral RNA is a key step in ensuring accurate detections. With many commercial RNA extraction kits and methodologies available, the performance of 4 different kits were evaluated for SARS-CoV-2 RNA detection in wastewater, specifically focusing on their applicability to lower population densities such as those at university campus dorms. Raw wastewater samples were collected at 4 sites on a college campus over a 24 hour period as a composite sample. Included in these sites was an isolation site that housed students that tested positive for Covid-19 via nasopharyngeal swabs. These samples were analyzed using the following kits: Qiagen All Prep PowerViral DNA/RNA kit, New England BioLabs Monarch RNA MiniPrep Kit, and Zymo Quick RNA-Viral Kit, and the Zymo Quick-RNA Fecal/Soil Microbe MicroPrep Kit. All four sites were processed according to the manufacturer's guidelines. Extractions were then quantified with RT-qPCR one-step reactions using an N2 primer and a linearized plasmid standard. While the Zymo Quick-RNA Fecal/Soil Microbe MicroPrep Kit (also known as the Zymo Environ Water RNA Kit) only recovered approximately 73% (±38%) SARS-CoV-2 RNA compared to the Zymo Quick-RNA Viral kit, it was the most time efficient kit to yield comparable results. This extraction kit had a cumulative processing time of approximately 5 h compared, while the other three kits had processing times between approximately 9 and 9.5 h. Based on the current research, the most effective kits for smaller population densities are pellet based and include a homogenization, inhibitor removal, and RNA preservation step.

A vitamin D enriched diet attenuates sex-specific behavioral deficits, increases the lifespan, but does not rescue bone abnormalities in a mouse model of cortical dysplasia

Individuals who experience recurrent spontaneous seizures often show behavioral and physiological comorbidities. Those with epilepsy are at a high risk of bone fractures (independent of seizure-related falls) and show a higher rate of a diagnosis of Autism Spectrum Disorder. The neural subset-specific (NS) Pten knockout (KO) mouse has an epilepsy phenotype, has been characterized to show autistic-like deficits, and has an osteoporosis phenotype. The current study examined the effect of a vitamin D enriched diet (20,000 IU VD) in the NS-Pten KO and wildtype mice. Mice were placed onto a vitamin D enriched diet at 4 weeks of age and maintained on that diet throughout testing. Behavioral testing began at 6 weeks of age and included tests for general activity, anxiety, repetitive behaviors, social behaviors, and memory. Results indicated that a vitamin D diet attenuated hypoactivity levels in male KO mice (p < 0.05). In a social partition task, vitamin D increased sociability in male wildtype mice, (p < 0.05). Most significantly, vitamin D fortified diet increased percent survival in KO animals and decreased the level of microglia marker IBA-1 and mTOR (mammalian target of rapamycin) downstream targets pS6 and pAKT. A high vitamin D diet did not reverse bone deficits in male or female KO mice. Overall, these findings suggest that a vitamin D enriched diet had a significant impact on the behavioral phenotype of NS-Pten KO mice, suggesting that dietary manipulations could be a potential therapeutic option for autistic-like behavior.

Rapamycin, but not minocycline, significantly alters ultrasonic vocalization behavior in C57BL/6J pups in a flurothyl seizure model

Epilepsy is one of the most common neurological disorders, with individuals having an increased susceptibility of seizures in the first few years of life, making children at risk of developing a multitude of cognitive and behavioral comorbidities throughout development. The present study examined the role of PI3K/Akt/mTOR pathway activity and neuroinflammatory signaling in the development of autistic-like behavior following seizures in the neonatal period. Male and female C57BL/6J mice were administered 3 flurothyl seizures on postnatal (PD) 10, followed by administration of minocycline, the mTOR inhibitor rapamycin, or a combined treatment of both therapeutics. On PD12, isolation-induced ultrasonic vocalizations (USVs) of mice were examined to determine the impact of seizures and treatment on communicative behaviors, a component of the autistic-like phenotype. Seizures on PD10 increased the quantity of USVs in female mice and reduced the amount of complex call types emitted in males compared to controls. Inhibition of mTOR with rapamycin significantly reduced the quantity and duration of USVs in both sexes. Changes in USVs were associated with increases in mTOR and astrocyte levels in male mice, however, three PD10 seizures did not result in enhanced proinflammatory cytokine expression in either sex. Beyond inhibition of mTOR activity by rapamycin, both therapeutics did not demonstrate beneficial effects. These findings emphasize the importance of differences that may exist across preclinical seizure models, as three flurothyl seizures did not induce as drastic of changes in mTOR activity or inflammation as observed in other rodent models.

Prenatal High-Fat Diet Rescues Communication Deficits in Fmr1 Mutant Mice in a Sex-Specific Manner

Using high-throughput analysis methods, the present study sought to determine the impact of prenatal high-fat dietary manipulations on isolation-induced ultrasonic vocalization production in both male and female Fmr1mutants on postnatal day 9. Prior to breeding, male FVB/129 Fmr1 wildtype and female Fmr1 heterozygous breeding pairs were assigned to 1 of 3 diet conditions: standard lab chow, omega-3 fatty acid-enriched chow, and a diet controlling for the fat increase. Prenatal exposure to omega-3 fatty acids improved reductions in the number of calls produced by Fmr1heterozygotes females. Moreover, diminished spectral purity in the female Fmr1homozygous mouse was rescued by exposure to both high-fat diets, although these effects were not seen in the male Fmr1knockout. Prenatal dietary fat manipulation also influenced several other aspects of vocalization production, such as the number of calls produced and their fundamental frequency, aside from effects due to loss of Fmr1.Specifically, in males, regardless of genotype, prenatal exposure to high omega-3s increased the average fundamental frequency of calls. These data support the need for future preclinical and clinical work elucidating the full potential of prenatal high-fat diets as a novel therapeutic alternative forFragile X syndrome.

A comparison of the Avisoft (v.5.2) and MATLAB Mouse Song Analyzer (v.1.3) vocalization analysis systems in C57BL/6, Fmr1-FVB.129, NS-Pten-FVB, and 129 mice

BACKGROUND

Communicative behaviors play a vital role in mammals and are highly relevant to human neurodevelopmental conditions. Mice produce communicative vocalizations that occur in the ultrasonic range, which are commonly analyzed within the Avisoft recording system. Fully automated programs such as the Mouse Song Analyzer in MATLAB, have been developed to analyze USVs in a shorter time period, however, no study has compared the accuracy of MATLAB to Avisoft.

NEW METHOD

In order to determine MATLAB's accuracy, we used data from four different mouse strains and assessed whether the total number of USVs detected was similar between systems.

RESULTS

We found that there was a high correlation between systems for the number of USVs emitted from C57BL/6 and NS-Pten mice however, Avisoft detected significantly more USVs than MATLAB for both strains. For Fmr1-FVB.129 and 129 mice, large correlations were observed between systems and no significant difference was present in the USVs detected. A partial correlation was run to control for the covariates: sex, age, strain, and treatment, and found that only strain substantially influences the relationship between the USVs detected in Avisoft and those detected in MATLAB.

COMPARISON WITH EXISTING METHOD

These findings demonstrate that there is a high degree of agreement between Avisoft and the Mouse Song Analyzer however, Avisoft does detect significantly more USVs depending on the strain assessed.

CONCLUSIONS

Therefore, there are relative advantages and disadvantages with both systems that vocalization researchers should be aware of when interpreting USV results, and when using either system.

A single episode of early-life status epilepticus impacts neonatal ultrasonic vocalization behavior in the Fmr1 knockout mouse

Fragile X syndrome (FXS) is a genetic disorder caused by a trinucleotide (CGG) expansion mutation in the Fmr1 gene located on the X chromosome. It is characterized by hyperactivity, increased anxiety, repetitive-stereotyped behaviors, and impaired language development. Many children diagnosed with FXS also experience seizures during their lifetime. However, the underlying etiology of the relationship between FXS and epilepsy is not fully understood. Ultrasonic vocalizations (UVs) are one tool that may be used to measure early behavioral changes in mouse pups. In the present study, neonatal UVs were analyzed as a measure of communicative behavior in a mouse model of FXS, both with and without early-life seizures (ELSs). On postnatal day (PD) 10, status epilepticus (SE) was induced via intraperitoneal injections of 0.5% kainic acid (2.0 mg/kg) in male Fmr1 knockout (KO) and wild-type (WT) mice. On PD 12, all pups were temporarily isolated from their dam and UVs were recorded. Significant alterations were found in both spectral and temporal measures across genotype and seizure groups. Early-life seizure experience resulted in a significant increase in the quantity of UVs only in WT animals (p < 0.05). We also found that while there was no difference between genotypes in the total number of vocalizations made, calls produced by Fmr1 KO mice were significantly shorter and had a higher peak frequency compared with WT mice. Overall, these findings support the use of vocalization behavior as an early phenotypic marker and highlight the importance of utilizing double-hit models to better understand comorbid disorders.

An acute seizure prior to memory reactivation transiently impairs associative memory performance in C57BL/6J mice

Memory deficits significantly decrease an individual's quality of life and are a pervasive comorbidity of epilepsy. Despite the various distinct processes of memory, the majority of epilepsy research has focused on seizures during the encoding phase of memory, therefore the effects of a seizure on other memory processes is relatively unknown. In the present study, we investigated how a single seizure affects memory reactivation in C57BL/6J adult mice using an associative conditioning paradigm. Initially, mice were trained to associate a tone (conditioned stimulus), with the presence of a shock (unconditioned stimulus). Flurothyl was then administered 1 h before, 1 h after, or 6 h before a memory reactivation trial. The learned association was then assessed by presenting a conditioned stimulus in a new context 24 h or 1 wk after memory reactivation. We found that mice receiving a seizure 1 h prior to reactivation exhibited a deficit in memory 24 h later but not 1 wk later. When mice were administered a seizure 6 h before or 1 h after reactivation, there were no differences in memory between seizure and control animals. Altogether, our study indicates that an acute seizure during memory reactivation leads to a temporary deficit in associative memory in adult mice. These findings suggest that the cognitive impact of a seizure may depend on the timing of the seizure relative to the memory process that is active.

NS-Pten adult knockout mice display both quantitative and qualitative changes in urine-induced ultrasonic vocalizations

The NS-Pten knockout (KO) mouse exhibits hyperactivity of the mammalian target of rapamycin (mTOR) and is a model of autism spectrum disorder (ASD). ASD presents with marked deficits in communication which can be elucidated by investigating their counterpart in mice, ultrasonic vocalizations (USVs). While USVs have been found to be altered in NS-Pten KO pups, no study has assessed whether this communication deficit persists into adulthood. In the present study, we investigate female urine-induced USVs, scent marking behavior, and open field activity in NS-Pten KO and wildtype (WT) adult male mice. Results showed that there was no difference in the quantity of vocalizations produced between groups, however, there were extensive alterations in the spectral properties of USVs. KO mice emitted vocalizations of a lower peak frequency, shorter duration, and higher peak amplitude compared to WT mice. KO animals also emitted a significantly different distribution of call-types relative to controls, displaying increased complex and short calls, but fewer upward, chevron, frequency steps, and composite calls. No significant differences between groups were observed for scent marking behavior and there was no difference between groups in the amount of time spent near the female urine. Overall, this study demonstrated that mTOR hyperactivity contributes to communication deficits in adult mice.

Lipopolysaccharide-induced inflammation leads to acute elevations in pro-inflammatory cytokine expression in a mouse model of Fragile X syndrome

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a single genetic mutation in the Fmr1 gene, serving as the largest genetic cause of intellectual disability. Trinucleotide expansion mutations in Fmr1 result in silencing and hypermethylation of the gene, preventing synthesis of the RNA binding protein Fragile X mental retardation protein which functions as a translational repressor. Abnormal immune responses have been demonstrated to play a role in FXS pathophysiology, however, whether these alterations impact how those with FXS respond to an immune insult behaviorally is not entirely known. In the current study, we examine how Fmr1 knockout (KO) and wild type (WT) mice respond to the innate immune stimulus lipopolysaccharide (LPS), both on a molecular and behavioral level, to determine if Fmr1 mutations impact the normal physiological response to an immune insult. In response to LPS, Fmr1 KO mice had elevated hippocampal IL-1β and IL-6 mRNA levels 4 h post-treatment compared to WT mice, with no differences detected in any cytokines at baseline or between genotypes 24 h post-LPS administration. Fmr1 KO mice also had upregulated hippocampal BDNF gene expression 4 h post-treatment compared to WT mice, which was not dependent on LPS administration. There were no differences in hippocampal protein expression between genotypes in microglia (Iba1) or astrocyte (GFAP) reactivity. Further, both genotypes displayed the typical sickness response following LPS stimulation, demonstrated by a significant reduction in food burrowed by LPS-treated mice in a burrowing task. Additional investigation is critical to determine if the transient increases in cytokine expression could lead to long-term changes in downstream molecular signaling in FXS.

High-throughput analysis of vocalizations reveals sex-specific changes in Fmr1 mutant pups

There have been several reports that individuals with Fragile X syndrome (FXS) and animal models of FXS have communication deficits. The present study utilized two different call classification taxonomies to examine the sex-specificity of ultrasonic vocalization (USV) production on postnatal day (PD8) in the FVB strain of Fmr1 knockout (KO) mice. One classification protocol requires the investigator to score each call by hand, while the other protocol uses an automated algorithm. Results using the hand-scoring protocol indicated that male Fmr1 KO mice exhibited longer calls (P = .03) than wild types on PD8. Male KOs also produced fewer complex, composite, downward, short and two-syllable call-types, as well as more frequency steps and chevron call-types. Female heterozygotes exhibited no significant changes in acoustic or temporal aspects of calls, yet showed significant changes in call-type production proportions across two different classification taxonomies (P < .001). They exhibited increased production of harmonic and frequency steps calls, as well as fewer chevron, downward and short calls. According to the second high-throughput analysis, female heterozygotes produced significantly fewer single-type and more multiple-type syllables, unlike male KOs that showed no changes in these aspects of syllable production. Finally, we correlated both scoring methods and found a high level of correlation between the two methods. These results contribute further knowledge of sex differences in USV calling behavior for Fmr1 heterozygote and KO mice and provide a foundation for the use of high-throughput analysis of neonatal USVs.

High seizure load during sensitive periods of development leads to broad shifts in ultrasonic vocalization behavior in neonatal male and female C57BL/6J mice

There is increasing evidence that seizures during early development can impact ultrasonic vocalizations (USVs) emitted from neonatal mice. However, most of the effects of early-life seizures have been reported using chemoconvulsants that produce continuous seizures (status epilepticus). In the present study, we evaluated the impact of different seizure frequency loads during early-life vocalization development in C57BL/6J male and female mice. For the high seizure load (HSL) paradigm, we administered 3 flurothyl seizures to mice on postnatal day (PD) 7 through PD11, and recorded USVs on PD12. We found that the induction of seizures across PD7-11 resulted in increased average duration (P < 0.05) and cumulative duration (P < 0.05) of USVs across both sexes. Call-type analyses indicated several call-type changes, including reduced production of complex call-types from males' HSL condition. For the low seizure load (LSL) paradigm, we induced 3 flurothyl seizures only on PD10 and recorded USVs on PD12. We found no change in any spectral or temporal features of USVs. However, call-type production analyses indicated that both male and female animals from the LSL paradigm also produced changes in call-types. This study provides evidence that the magnitude of communication impairment following seizures is significantly impacted by seizure frequency load early in development.

A single seizure selectively impairs hippocampal-dependent memory and is associated with alterations in PI3K/Akt/mTOR and FMRP signaling

Objective

A single brief seizure before learning leads to spatial and contextual memory impairment in rodents without chronic epilepsy. These results suggest that memory can be impacted by seizure activity in the absence of epilepsy pathology. In this study, we investigated the types of memory affected by a seizure and the time course of impairment. We also examined alterations to mammalian target of rapamycin (mTOR) and fragile X mental retardation protein (FMRP) signaling, which modulate elements of the synapse and may underlie impairment.

Methods

We induced a single seizure and investigated hippocampal and nonhippocampal memory using trace fear conditioning, novel object recognition (NOR), and accelerating rotarod to determine the specificity of impairment in mice. We used western blot analysis to examine for changes to cellular signaling and synaptic proteins 1 h, 24 h, and 1 week after a seizure. We also included a histologic examination to determine if cell loss or gross lesions might alternatively explain memory deficits.

Results

Behavioral results indicated that a seizure before learning leads to impairment of trace fear memory that worsens over time. In contrast, nonhippocampal memory was unaffected by a seizure in the NOR and rotarod tasks. Western analysis indicated increased hippocampal phospho‐S6 and total FMRP 1 h following a seizure. Tissue taken 24 h after a seizure indicated increased hippocampal GluA1, suggesting increased α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor expression. Histologic analysis indicated that neither cell loss nor lesions are present after a single seizure.

Significance

The presence of memory impairment in the absence of damage suggests that memory impairment caused by seizure activity differs from general memory impairment in epilepsy. Instead, memory impairment after a single seizure is associated with alterations to mTOR and FMRP signaling, which leads to a disruption of synaptic proteins involved in consolidation of long‐term memory. These results have implications for understanding memory impairment in epilepsy.

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

Neuroinflammation is consistently found in many neurological disorders, but whether or not the inflammatory response independently affects neuronal network properties is poorly understood. Here, we report that intracerebroventricular injection of the prototypical inflammatory molecule lipopolysaccharide (LPS) in rats triggered a strong and long-lasting inflammatory response in hippocampal microglia associated with a concomitant upregulation of Toll-like receptor (TLR4) in pyramidal and hilar neurons. This, in turn, was associated with a significant reduction of the dendritic hyperpolarization-activated cyclic AMP-gated channel type 1 (HCN1) protein level while Kv4.2 channels were unaltered as assessed by western blot. Immunohistochemistry confirmed the HCN1 decrease in CA1 pyramidal neurons and showed that these changes were associated with a reduction of TRIP8b, an auxiliary subunit for HCN channels implicated in channel subcellular localization and trafficking. At the physiological level, this effect translated into a 50% decrease in HCN1-mediated currents (Ih) measured in the distal dendrites of hippocampal CA1 pyramidal cells. At the functional level, the band-pass-filtering properties of dendrites in the theta frequency range (4-12 Hz) and their temporal summation properties were compromised. We conclude that neuroinflammation can independently trigger an acquired channelopathy in CA1 pyramidal cell dendrites that alters their integrative properties. By directly changing cellular function, this phenomenon may participate in the phenotypic expression of various brain diseases.

Neuronal subset-specific deletion of Pten results in aberrant Wnt signaling and memory impairments

The canonical Wnt and PI3K/Akt/mTOR pathways both play critical roles in brain development early in life. There is extensive evidence of how each pathway is involved in neuronal and synaptic maturation, however, how these molecular networks interact requires further investigation. The present study examines the effect of neuronal subset-specific deletion of phosphatase and tensin homolog (Pten) in mice on Wnt signaling protein levels and associated cognitive impairments. PTEN functions as a negative regulator of the PI3K/Akt/mTOR pathway, and mutations in Pten can result in cognitive and behavioral impairments. We found that deletion of Pten resulted in elevated Dvl2, Wnt5a/b, and Naked2, along with decreased GSK3β hippocampal synaptosome protein expression compared to wild type mice. Aberrations in the canonical Wnt pathway were associated with learning and memory deficits in Pten knockout mice, specifically in novel object recognition and the Lashley maze. This study demonstrates that deletion of Pten not only significantly impacts PI3K/Akt/mTOR signaling, but affects proper functioning of the Wnt signaling pathway. Overall, these findings will help elucidate how the PI3K/Akt/mTOR pathway intersects with Wnt signaling to result in cognitive impairments, specifically in memory.

Wnt/β-catenin signaling as a potential target for novel epilepsy therapies

Epilepsy is one of the most common neurological disorders, and yet many afflicted individuals are resistant to all available therapeutic treatments. Existing pharmaceutical treatments function primarily to reduce hyperexcitability and prevent seizures, but fail to influence the underlying pathophysiology of the disorder. Recently, research efforts have focused on identifying alternative mechanistic targets for anti-epileptogenic therapies that can prevent the development of chronic epilepsy. The Wnt/β-catenin pathway, one possible target, has been demonstrated to be disrupted in both acute and chronic phases of epilepsy. Wnt/β-catenin signaling can regulate many seizure-induced changes in the brain, including neurogenesis and neuronal death, as well as can influence seizure susceptibility and potentially the development of chronic epilepsy. Several genome-wide studies and in vivo knockout animal models have provided evidence for an association between disrupted Wnt/β-catenin signaling and epilepsy. Furthermore, approved pharmaceutical drugs and other small molecule compounds that target components of the β-catenin destruction complex or antagonize endogenous inhibitors of the pathway have shown to be protective following seizures. However, additional studies are needed to determine the optimal time period in which modulation of the pathway may be most beneficial. Overall, disrupted molecular networks such as Wnt/β-catenin signaling, could be a promising anti-epileptogenic target for future epilepsy therapies.

Reversal learning paradigm reveals deficits in cognitive flexibility in the Fmr1 knockout male mouse

Background: Loss of FMR1 is associated with Fragile X syndrome, amongst the most prevalent inherited intellectual disability. Despite extensive research in this area, previous studies have failed to detect consistent evidence of cognitive impairments in the Morris water maze (MWM) task in the Fmr1 knockout (KO) mouse. However, few studies have examined cognitive flexibility in a reversal form of the MWM task, which may illuminate subtle learning deficits. Methods: Adult male Fmr1 wildtype (WT) and KO mice were bred and tested in the MWM reversal paradigm. The testing paradigm consisted of two blocks per day, with 4 trials per block to locate a hidden platform. After the last trials on the fourth day of testing, the animals were given a probe trial with the platform removed. The following week, the location of the platform was switched to the opposite quadrant and the animals received 2 more days of testing, with 4 blocks in total. Results: As expected, Fmr1 KO mice did not display a learning deficit during the acquisition phase, F genotype (1, 24) = 0.034, p = 0.854, and performed similarly on the probe trial, F genotype (1, 23) = 0.024, p = 0.877. However, during the reversal phase of learning, Fmr1 KO mice showed deficits in their ability to learn the new location of the platform, F genotype (1, 23) = 3.93, p = 0.059. Further independent samples t-testing revealed that KO animals displayed significantly higher latency to reach the hidden platform during the third trial, t(23) = -2.96, p < 0.01. Conclusions: While previous studies have not demonstrated deficits in spatial memory in the Fmr1 KO model, it is possible that the acquisition phase of the task is less sensitive to deficits in learning. Future studies using this model to evaluate therapeutic interventions should consider utilizing the MWM reversal paradigm.

NS-Pten knockout mice show sex- and age-specific differences in ultrasonic vocalizations

OBJECTIVE

The goal of this study was to identify changes in quantitative and qualitative aspects of neonatal ultrasonic vocalizations USVs in neuron-subset specific (NS-Pten) knockout males and females when compared with wild-type male and female mice.

BACKGROUND

One signaling cascade that plays a crucial role in the development of an autistic-like phenotype is the PI3K/Akt/mTOR pathway. Mouse models that illustrate this connection include Fmr1, Tsc1, and NS-Pten-deficient mice. While numerous studies have investigated ultrasonic vocalizations in Fmr1 knockout and Tsc1 heterogenous mice, none have investigated USVs in NS-Pten knockout mice using a full spectrum recording system.

METHODS

We recorded ultrasonic vocalizations from NS-Pten wild-type and knockout male and female mice on postnatal days 8 and 11. On these days, we measured the number and quality of calls emitted from pups when they were removed from their mothers.

RESULTS

We found that knockout pups emitted fewer vocalizations for both sexes (p < .05). Knockout males had calls of a shorter duration and lower peak amplitude on day 8, while showing a shorter duration, lower peak amplitude, and higher peak and fundamental frequency on day 11 (p < .001). Knockout females vocalized at a lower peak amplitude and fundamental frequency, and a higher peak frequency on day 8, while showing a shorter duration and a higher peak and fundamental frequency on day 11 (p < .001). Spectrographic analyses also revealed significant differences in call type for both genotypes and sexes (p < .05).

CONCLUSIONS

These findings demonstrate that deletion of NS-Pten results in significant decreases in vocalizations across both sexes. Additionally, our findings indicate that the aberrant vocalizations and increased call duration seen in other mTOR models are also present in NS-Pten knockout mice. Our study provides evidence of a connection between hyperactive mTOR signaling and neonatal ultrasonic vocalizations.

Deletion of Fmr1 results in sex-specific changes in behavior

OBJECTIVE

In this study, we used a systemic Fmr1 knockout in order to investigate both genotype- and sex-specific differences across multiple measures of sociability, repetitive behaviors, activity levels, anxiety, and fear-related learning and memory.

BACKGROUND

Fragile X syndrome is the most common monogenic cause of intellectual disability and autism. Few studies to date have examined sex differences in a mouse model of Fragile X syndrome, though clinical data support the idea of differences in both overall prevalence and phenotype between the sexes.

METHODS

Using wild-type and systemic homozygous Fmr1 knockout mice, we assessed a variety of behavioral paradigms in adult animals, including the open field test, elevated plus maze, nose-poke assay, accelerating rotarod, social partition task, three-chambered social task, and two different fear conditioning paradigms. Tests were ordered such that the most invasive tests were performed last in the sequence, and testing paradigms for similar behaviors were performed in separate cohorts to minimize testing effects.

RESULTS

Our results indicate several sex-specific changes in Fmr1 knockout mice, including male-specific increases in activity levels, and female-specific increases in repetitive behaviors on both the nose-poke assay and motor coordination on the accelerating rotarod task. The results also indicated that Fmr1 deletion results in deficits in fear learning and memory across both sexes, and no changes in social behavior across two tasks.

CONCLUSION

These findings highlight the importance of including female subjects in preclinical studies, as simply studying the impact of genetic mutations in males does not yield a complete picture of the phenotype. Further research should explore these marked phenotypic differences among the sexes. Moreover, given that treatment strategies are typically equivalent between the sexes, the results highlight a potential need for sex-specific therapeutics.

Oral aniracetam treatment in C57BL/6J mice without pre-existing cognitive dysfunction reveals no changes in learning, memory, anxiety or stereotypy

Background: The piracetam analog, aniracetam, has recently received attention for its cognition enhancing potential, with minimal reported side effects.  Previous studies report the drug to be effective in both human and non-human models with pre-existing cognitive dysfunction, but few studies have evaluated its efficacy in healthy subjects. A previous study performed in our laboratory found no cognitive enhancing effects of oral aniracetam administration 1-hour prior to behavioral testing in naïve C57BL/6J mice. Methods: The current study aims to further evaluate this drug by administration of aniracetam 30 minutes prior to testing in order to optimize any cognitive enhancing effects. In this study, all naïve C57BL/6J mice were tested in tasks of delayed fear conditioning, novel object recognition, rotarod, open field, elevated plus maze, and marble burying. Results: Across all tasks, animals in the treatment group failed to show enhanced learning when compared to controls. Conclusions: These results provide further evidence suggesting that aniracetam conveys no therapeutic benefit to subjects without pre-existing cognitive dysfunction.

Oral aniracetam treatment in C57BL/6J mice without pre-existing cognitive dysfunction reveals no changes in learning, memory, anxiety or stereotypy

Background: The piracetam analog, aniracetam, has recently received attention for its cognition enhancing potential, with minimal reported side effects.  Previous studies report the drug to be effective in both human and non-human models with pre-existing cognitive dysfunction, but few studies have evaluated its efficacy in healthy subjects. A previous study performed in our laboratory found no cognitive enhancing effects of oral aniracetam administration 1-hour prior to behavioral testing in naïve C57BL/6J mice. Methods: The current study aims to further evaluate this drug by administration of aniracetam 30 minutes prior to testing in order to optimize any cognitive enhancing effects. In this study, all naïve C57BL/6J mice were tested in tasks of delayed fear conditioning, novel object recognition, rotarod, open field, elevated plus maze, and marble burying. Results: Across all tasks, animals in the treatment group failed to show enhanced learning when compared to controls. Conclusions: These results provide further evidence suggesting that aniracetam conveys no therapeutic benefit to subjects without pre-existing cognitive dysfunction.

Study of oral aniracetam in C57BL/6J mice without pre-existing cognitive impairments

BACKGROUND

The piracetam analog, aniracetam, has recently received attention for its cognition enhancing potential, with minimal reported side effects.  Previous studies report the drug to be effective in both human and non-human models with pre-existing cognitive dysfunction, but few studies have evaluated its efficacy in healthy subjects. A previous study performed in our laboratory found no cognitive enhancing effects of oral aniracetam administration 1-hour prior to behavioral testing in naïve C57BL/6J mice.

METHODS

The current study aims to further evaluate this drug by administration of aniracetam 30 minutes prior to testing in order to optimize any cognitive enhancing effects. In this study, all naïve C57BL/6J mice were tested in tasks of delayed fear conditioning, novel object recognition, rotarod, open field, elevated plus maze, and marble burying.

RESULTS

Across all tasks, animals in the treatment group failed to show enhanced learning when compared to controls.

CONCLUSIONS

These results provide further evidence suggesting that aniracetam conveys no therapeutic benefit to subjects without pre-existing cognitive dysfunction.

Early-life status epilepticus acutely impacts select quantitative and qualitative features of neonatal vocalization behavior: Spectrographic and temporal characterizations in C57BL/6 mice

Early-life seizures are known to cause long-term deficits in social behavior, learning, and memory, however little is known regarding their acute impact. Ultrasonic vocalization (USV) recordings have been developed as a tool for investigating early communicative deficits in mice. Previous investigation from our lab found that postnatal day (PD) 10 seizures cause male-specific suppression of 50-kHz USVs on PD12 in 129 SvEvTac mouse pups. The present study extends these findings by spectrographic characterization of USVs following neonatal seizures. On PD10, male C57BL/6 pups were administered intraperitoneal injections of kainic acid or physiological saline. On PD12, isolation-induced recordings were captured using a broad-spectrum ultrasonic microphone. Status epilepticus significantly suppressed USV quantity (p=0.001) and total duration (p<0.05). Seizure pups also utilized fewer complex calls than controls (p<0.05). There were no changes in call latency or inter-call intervals. Spectrographic analysis revealed increased peak amplitude for complex, downward, short, two-syllable, and upward calls, as well as reduced mean duration for short and two-syllable calls in seizure mice. This investigation provides the first known spectrographic characterization of USVs following early-life seizures. These findings also enhance evidence for USVs as an indicator of select communicative impairment.

Spectral and temporal properties of calls reveal deficits in ultrasonic vocalizations of adult Fmr1 knockout mice

The Fmr1 knockout (KO) mouse has commonly been used to investigate communication impairments, one of the key diagnostic symptoms observed in Fragile X syndrome (FXS) and Autism spectrum disorder (ASD). Many studies have found alterations in ultrasonic vocalizations (USVs) in neonatal Fmr1 KO mice, however, there is limited research investigating whether these deficits continue into adulthood. In the present study, we examine differences in female urine-induced ultrasonic vocalizations, scent marking behavior, odor discrimination, and open field activity in adult male Fmr1 KO and wildtype (WT) mice. Overall, we found extensive alterations between genotypes in both spectral and temporal properties of ultrasonic vocalizations. There was no difference in the average number of calls emitted by both genotypes, however, Fmr1 KO mice emitted calls of a higher frequency, decreased amplitude, and shorter duration than WT mice. Spectrographic analyses revealed statistically significant differences between genotypes in the types of calls emitted. Contrastingly, we found no differences in scent marking behavior, a form of social communication, or in odor discrimination and activity levels of the mice. The results corroborate previous studies emphasizing the importance of qualitative differences observed in vocalization behavior of Fmr1 KO mice, rather than quantitative measurements such as number of calls emitted. Overall, the study confirms the presence of abnormalities in vocalization behavior in adult Fmr1 KO mice that we believe are consistent with communication deficits seen in the syndrome.

Early-life status epilepticus induces long-term deficits in anxiety and spatial learning in mice

Background

One of the most devastating aspects of developmental epilepsy is the long-term impact on behavior. Children with epilepsy show a high co-morbidity with anxiety disorders and autism.

Methods

To examine whether early-life status epilepticus results in altered anxiety, repetitive behavior, social behavior, and learning and memory, we induced status epilepticus in male C57BL/6 mice on postnatal day (PD) 10. The mice received intraperitoneal injections of either kainic acid (2mg/kg) or 0.9% normal saline. We also included a nontreated control group. Kainic acid induced status epilepticus for approximately 1.5 hrs. At PD60, the adult mice were then tested in a battery of behavioral tasks, including open field activity, elevated-plus maze, light-dark test, marble burying, social chamber, social partition, conditioned fear, novel object recognition, and Morris water maze.

Results

The early-life seizure group showed consistent increases in anxiety in the open field test (p < 0.05), elevated plus maze (p < 0.05), and light-dark task (p < 0.01). The seizure group showed significant (p < 0.01) impairment in the Morris water maze. There were no differences observed in marble burying, social partition, social chamber, novel object recognition, or delay fear conditioning tasks.

Conclusions

These results demonstrate that a single insult of status epilepticus during the neonatal period is sufficient to cause specific, long-term impairments in anxiety and spatial learning.

Kv4.2 knockout mice display learning and memory deficits in the Lashley maze

Background: Potassium channels have been shown to be involved in neural plasticity and learning. Kv4.2 is a subunit of the A-type potassium channel. Kv4.2 channels modulate excitability in the dendrites of pyramidal neurons in the cortex and hippocampus. Deletion of Kv4.2 results in spatial learning and conditioned fear deficits; however, previous studies have only examined deletion of Kv4.2 in aversive learning tests. Methods: For the current study, we used the Lashley maze as an appetitive learning test. We examined Kv4.2 wildtype (WT) and knockout (KO) mice in the Lashley maze over 4 days during adulthood. The first day consisted of habituating the mice to the maze. The mice then received five trials per day for the next 3 days. The number of errors and the time to the goal box was recorded for each trial. The goal box contained a weigh boat with an appetitive reward (gelatin with sugar). There was an intertrial interval of 15 minutes. Results: We found that Kv4.2 KO mice committed more errors across the trials compared to the WT mice p<0.001. There was no difference in the latency to find the goal box over the period. Discussion: Our finding that deletion of Kv4.2 resulted in more errors in the Lashley maze across 15 trials contribute to a growing body of evidence that Kv4.2 channels are significantly involved in learning and memory.

Kv4.2 knockout mice display learning and memory deficits in the Lashley maze

Background: Potassium channels have been shown to be involved in neural plasticity and learning. Kv4.2 is a subunit of the A-type potassium channel. Kv4.2 channels modulate excitability in the dendrites of pyramidal neurons in the cortex and hippocampus. Deletion of Kv4.2 results in spatial learning and conditioned fear deficits; however, previous studies have only examined deletion of Kv4.2 in aversive learning tests. Methods: For the current study, we used the Lashley maze as an appetitive learning test. We examined Kv4.2 wildtype (WT) and knockout (KO) mice in the Lashley maze over 4 days during adulthood. The first day consisted of habituating the mice to the maze. The mice then received five trials per day for the next 3 days. The number of errors and the time to the goal box was recorded for each trial. The goal box contained a weigh boat with an appetitive reward (gelatin with sugar). There was an intertrial interval of 15 minutes. Results: We found that Kv4.2 KO mice committed more errors across the trials compared to the WT mice p<0.001. There was no difference in the latency to find the goal box over the period. Discussion: Our finding that deletion of Kv4.2 resulted in more errors in the Lashley maze across 15 trials contribute to a growing body of evidence that Kv4.2 channels are significantly involved in learning and memory.

The effect of early life status epilepticus on ultrasonic vocalizations in mice

OBJECTIVE

Infant crying is a series of innate vocal patterns intended to elicit the attention of adult caregivers for fulfillment of specific needs such as pain, hunger, or hypostimulation. It is one of the earliest forms of observable communication. In neonatal rodents, this behavior has recently been investigated as a potential early behavioral marker of neural deficits in neurodevelopmental disorders. However, few studies have examined the effects of seizures on vocalization behavior during the neonatal period. The purpose of this study is to investigate the effect of a single kainate-induced early life seizure on vocalization behavior in mice. This study also investigates the subsequent effect of seizures on two pathways critical for early neural development and epileptogenesis: the phosphoinositide 3-kinase|serine/threonine kinase|mammalian target of rapamycin (PI3K-Akt-mTOR) and canonical (Wingless-Int Wnt) intracellular signaling pathways.

METHODS

On postnatal day 10, male and female 129SvEvTac mice received a single intraperitoneal injection of kainic acid (2.5 mg/kg) or vehicle injection. The kainate administration resulted in 1-2 h of status epilepticus. On postnatal days 11 and 12, the quantity and duration of isolation-induced ultrasonic vocalizations were recorded. Western blotting analyses were performed using male and female pups on postnatal day 12.

RESULTS

There was significant, male-specific suppression in the quantity and total duration of 50-kHz calls on postnatal day 12 following seizures. The hippocampi of male mice on this postnatal day also revealed male-specific changes in the PI3K-Akt-mTOR intracellular signaling pathway, as well as changes in phosphorylated fragile × mental retardation protein.

SIGNIFICANCE

These findings demonstrate that early life seizures can disrupt communication behavior in neonatal mice.

Effects of an acute seizure on associative learning and memory

Past studies have demonstrated that inducing several seizures or continuous seizures in neonatal or adult rats results in impairments in learning and memory. The impact of a single acute seizure on learning and memory has not been investigated in mice. In this study, we exposed adult 129SvEvTac mice to the inhalant flurothyl until a behavioral seizure was induced. Our study consisted of 4 experiments where we examined the effect of one seizure before or after delay fear conditioning. We also included a separate cohort of animals that was tested in the open field after a seizure to rule out changes in locomotor activity influencing the results of memory tests. Mice that had experienced a single seizure 1h, but not 6h, prior to training showed a significant impairment in associative conditioning to the conditioned stimulus when compared with controls 24h later. There were no differences in freezing one day later for animals that experienced a single seizure 1h after associative learning. We also found that an acute seizure reduced activity levels in an open-field test 2h but not 24h later. These findings suggest that an acute seizure occurring immediately before learning can have an effect on the recall of events occurring shortly after that seizure. In contrast, an acute seizure occurring shortly after learning appears to have little or no effect on long-term memory. These findings have implications for understanding the acute effects of seizures on the acquisition of new knowledge.

Comparison of Equivalence between Two Commercially Available S499-Phosphorylated FMRP Antibodies in Mice

Fragile X syndrome (FXS) develops from excessive trinucleotide CGG repeats in the 5’-untranslated region at Xq27.3 of the Fmr-1 gene, which functionally silences its expression and prevents transcription of its protein. This disorder is the most prominent form of heritable intellectual deficiency, affecting roughly 1 in 5,000 males and 1 in 10,000 females globally. Antibody specificity and selectivity are essential for investigating changes in intracellular protein signaling and phosphorylation status of the Fragile X Mental Retardation Protein (FMRP). Currently, both PhosphoSolutions^® and abcam® produce commercially available S499-phosphorylated FMRP specific antibodies. The antibody from PhosphoSolutions^® has been validated in previous studies; however, the antibody from abcam^® antibody has yet to receive similar validation. This study aims to determine whether these two antibodies are true equivalents through western blot analysis of both NS-Pten knockout (KO) and Fmr-1 KO mice strains. We prepared hippocampal synaptosomal preparations and probed the samples using total FMRP, abcam^® phosphorylated FMRP, and PhosphoSolutions^® phosphorylated FMRP antibodies. We found that there was a significant increase in phosphorylated FMRP levels using the abcam® and PhosphoSolutions^® antibodies in the NS-Pten KO mice compared to wildtype mice. However, there was much more variability using the abcam^® antibody. Furthermore, there was a band present in the Fmr-1 KO for the phosphorylated FMRP site using the abcam^® antibody for western blotting but not for the PhosphoSolutions^® antibody. Our findings strongly suggest that the antibody from abcam^® is neither specific nor selective for its advertised targeted substrate, S499-phosphorylated FMRP.

Testing for odor discrimination and habituation in mice

This video demonstrates a technique to establish the presence of a normally functioning olfactory system in a mouse. The test helps determine whether the mouse can discriminate between non-social odors and social odors, whether the mouse habituates to a repeatedly presented odor, and whether the mouse demonstrates dishabituation when presented with a novel odor. Since many social behavior tests measure the experimental animal's response to a familiar or novel mouse, false positives can be avoided by establishing that the animals can detect and discriminate between social odors. There are similar considerations in learning tests such as fear conditioning that use odor to create a novel environment or olfactory cues as an associative stimulus. Deficits in the olfactory system would impair the ability to distinguish between contexts and to form an association with an olfactory cue during fear conditioning. In the odor habitation/dishabituation test, the mouse is repeatedly presented with several odors. Each odor is presented three times for two minutes. The investigator records the sniffing time directed towards the odor as the measurement of olfactory responsiveness. A typical mouse shows a decrease in response to the odor over repeated presentations (habituation). The experimenter then presents a novel odor that elicits increased sniffing towards the new odor (dishabituation). After repeated presentation of the novel odor the animal again shows habituation. This protocol involves the presentation of water, two or more non-social odors, and two social odors. In addition to reducing experimental confounds, this test can provide information on the function of the olfactory systems of new knockout, knock-in, and conditional knockout mouse lines.

Deletion of PTEN produces autism-like behavioral deficits and alterations in synaptic proteins

Many genes have been implicated in the underlying cause of autism but each gene accounts for only a small fraction of those diagnosed with autism. There is increasing evidence that activity-dependent changes in neuronal signaling could act as a convergent mechanism for many of the changes in synaptic proteins. One candidate signaling pathway that may have a critical role in autism is the PI3K/AKT/mTOR pathway. A major regulator of this pathway is the negative repressor phosphatase and tensin homolog (PTEN). In the current study we examined the behavioral and molecular consequences in mice with neuron subset-specific deletion of PTEN. The knockout (KO) mice showed deficits in social chamber and social partition test. KO mice demonstrated alterations in repetitive behavior, as measured in the marble burying test and hole-board test. They showed no changes in ultrasonic vocalizations emitted on postnatal day 10 or 12 compared to wildtype (WT) mice. They exhibited less anxiety in the elevated-plus maze test and were more active in the open field test compared to WT mice. In addition to the behavioral alterations, KO mice had elevation of phosphorylated AKT, phosphorylated S6, and an increase in S6K. KO mice had a decrease in mGluR but an increase in total and phosphorylated fragile X mental retardation protein. The disruptions in intracellular signaling may be why the KO mice had a decrease in the dendritic potassium channel Kv4.2 and a decrease in the synaptic scaffolding proteins PSD-95 and SAP102. These findings demonstrate that deletion of PTEN results in long-term alterations in social behavior, repetitive behavior, activity, and anxiety. In addition, deletion of PTEN significantly alters mGluR signaling and many synaptic proteins in the hippocampus. Our data demonstrates that deletion of PTEN can result in many of the behavioral features of autism and may provide insights into the regulation of intracellular signaling on synaptic proteins.

Early-life seizures result in deficits in social behavior and learning

Children with epilepsy show a high co-morbidity with psychiatric disorders and autism. One of the critical determinants of a child's behavioral outcome with autism and cognitive dysfunction is the age of onset of seizures. In order to examine whether seizures during postnatal days 7-11 result in learning and memory deficits and behavioral features of autism we administered the inhalant flurothyl to induce seizures in C57BL/6J mice. Mice received three seizures per day for five days starting on postnatal day 7. Parallel control groups consisted of similarly handled animals that were not exposed to flurothyl and naïve mice. Subjects were then processed through a battery of behavioral tests in adulthood: elevated-plus maze, nose-poke assay, marble burying, social partition, social chamber, fear conditioning, and Morris water maze. Mice with early-life seizures had learning and memory deficits in the training portion of the Morris water maze (p<0.05) and probe trial (p<0.01). Mice with seizures showed no differences in marble burying, the nose-poke assay, or elevated plus-maze testing compared to controls. However, they showed a significant difference in the social chamber and social partition tests. Mice with seizures during postnatal days 7-11 showed a significant decrease in social interaction in the social chamber test and had a significant impairment in social behavior in the social partition test. Together, these results indicate that early life seizures result in deficits in hippocampal-dependent memory tasks and produce long-term disruptions in social behavior.

Trace fear conditioning in mice

In this experiment we present a technique to measure learning and memory. In the trace fear conditioning protocol presented here there are five pairings between a neutral stimulus and an unconditioned stimulus. There is a 20 sec trace period that separates each conditioning trial. On the following day freezing is measured during presentation of the conditioned stimulus (CS) and trace period. On the third day there is an 8 min test to measure contextual memory. The representative results are from mice that were presented with the aversive unconditioned stimulus (shock) compared to mice that received the tone presentations without the unconditioned stimulus. Trace fear conditioning has been successfully used to detect subtle learning and memory deficits and enhancements in mice that are not found with other fear conditioning methods. This type of fear conditioning is believed to be dependent upon connections between the medial prefrontal cortex and the hippocampus. One current controversy is whether this method is believed to be amygdala-independent. Therefore, other fear conditioning testing is needed to examine amygdala-dependent learning and memory effects, such as through the delay fear conditioning.

Deletion of PTEN produces deficits in conditioned fear and increases fragile X mental retardation protein

The phosphatase and tensin homolog detected on chromosome 10 (PTEN) gene product modulates activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway. The PI3K pathway has been found to be involved in the regulation of the fragile X mental retardation protein, which is important for long-term depression and in the formation of new memories. We used delayed fear conditioning and trace fear conditioning to determine learning and memory deficits in neuron subset-specific Pten (NS-Pten) conditional knockout (KO) mice. We found that NS-Pten KO mice had deficits in contextual learning and trace conditioning, but did not have deficits in the ability to learn a conditioned stimulus. Furthermore, we found increased levels in the total and phosphorylated forms of the fragile X mental retardation protein (FMRP) in the hippocampus of NS-Pten KO mice.

Rapamycin reverses status epilepticus-induced memory deficits and dendritic damage

Cognitive impairments are prominent sequelae of prolonged continuous seizures (status epilepticus; SE) in humans and animal models. While often associated with dendritic injury, the underlying mechanisms remain elusive. The mammalian target of rapamycin complex 1 (mTORC1) pathway is hyperactivated following SE. This pathway modulates learning and memory and is associated with regulation of neuronal, dendritic, and glial properties. Thus, in the present study we tested the hypothesis that SE-induced mTORC1 hyperactivation is a candidate mechanism underlying cognitive deficits and dendritic pathology seen following SE. We examined the effects of rapamycin, an mTORC1 inhibitor, on the early hippocampal-dependent spatial learning and memory deficits associated with an episode of pilocarpine-induced SE. Rapamycin-treated SE rats performed significantly better than the vehicle-treated rats in two spatial memory tasks, the Morris water maze and the novel object recognition test. At the molecular level, we found that the SE-induced increase in mTORC1 signaling was localized in neurons and microglia. Rapamycin decreased the SE-induced mTOR activation and attenuated microgliosis which was mostly localized within the CA1 area. These findings paralleled a reversal of the SE-induced decreases in dendritic Map2 and ion channels levels as well as improved dendritic branching and spine density in area CA1 following rapamycin treatment. Taken together, these findings suggest that mTORC1 hyperactivity contributes to early hippocampal-dependent spatial learning and memory deficits and dendritic dysregulation associated with SE.