Contextual and cued fear conditioning test using a video analyzing system in mice

Age-related behavioral changes from young to old age in male mice of a C57BL/6J strain maintained under a genetic stability program

AIM

Aging is thought to coincide with gradual and progressive changes in brain function and behavior over the lifetime. Our previous meta-analytic study reported age-related behavioral changes from young to middle age in male C57BL/6J mice. However, the previous study had some limitations that could affect the generalizability of the findings because of the potential influence of genetic and environmental factors on behavior, in addition to a lack of information regarding the behaviors of old-aged mice. Here, to investigate age-related behavioral changes from young to old age in mice, we analyzed the behaviors of male C57BL/6J mice from four different age groups (8, 47, 73, and 99 weeks of age at the beginning of the experiment) from a colony that had been maintained in a genetically controlled condition based on The Jackson Laboratory's Genetic Stability Program in an environmentally controlled animal facility.

METHODS

We used a battery of behavioral tests, including the light/dark transition, open field, elevated plus maze, hot plate, social interaction, rotarod, three-chamber social approach, prepulse inhibition, Porsolt forced swim, T-maze, Barnes maze, tail suspension, and fear-conditioning tests.

RESULTS

Some behavioral changes occurred between young and middle age, and further changes in various behaviors were observed in old age. Decreased locomotor activity and increased anxiety-like behavior were found in old-aged mice compared to those in young and middle-aged mice in the light/dark transition test. Similarly, an age-dependent decrease in locomotor activity was observed in the open field test and the elevated plus maze test, while there was an age-dependent increase in the time spent in the center area in the open field test and there were no significant differences among age groups in behavioral measures of anxiety in the elevated plus maze test. Decreases in motor performance and the auditory startle response were found in middle-aged mice compared to those in young mice. Similar behavioral changes and increased pain sensitivity, decreased social novelty preference, reduced working and spatial memory, and impaired cued fear memory were observed in old-aged mice compared to those in young mice. Prepulse inhibition was higher in middle-aged mice than in young and old-aged mice. Age-related changes in depression-related behavior were dependent on the type of test and the test time period.

CONCLUSIONS

This study generally confirmed our previous report regarding age-related behavioral changes from young to middle age and expanded the previous observations by examining the behaviors of old-aged mice. Our results show age-related changes in a wide range of behaviors in mice from young to old age. Most behaviors showed gradual changes with advancing age, but some types of behaviors, such as vertical activity, prepulse inhibition, and depression-related behavior, did not show unidirectional changes with age. These findings provide basic information about the behavioral characteristics of young, middle-aged, and aged male C57BL/6J mice.

N-Acetyl Serotonin Protects Neural Progenitor Cells Against Oxidative Stress-Induced Apoptosis and Improves Neurogenesis in Adult Mouse Hippocampus Following Traumatic Brain Injury

In this study, with primary mouse neural progenitor cells (NPCs), we investigated the neuroprotective effect of a tropomyosin-related kinase receptor B (TrkB) agonist, N-acetyl serotonin (NAS), against hydrogen peroxide (H₂O₂)-induced toxicity. We found that pre-incubation with NAS not only ameliorates H₂O₂-induced cell viability loss, lactate dehydrogenase (LDH) release, and proliferative and migratory capacity impairments, but counteracts H₂O₂-triggered production of nitric oxide (NO), reactive oxygen species (ROS), malondialdehyde (MDA), and 8-hydroxy-deoxyguanosine (8-OHdG) in a dose-dependent manner. Additionally, pre-treatment with NAS was able to attenuate H₂O₂-induced apoptosis in NPCs, evidenced by the decreased percentage of apoptotic cells and altered expression of apoptosis-related factors. Furthermore, in differentiated NPCs, NAS improves H₂O₂-induced reduction in neurite growth. Mechanistic studies revealed that the protective effects of NAS in NPCs may be mediated by the TrkB/PI3K/Akt/ cAMP response element binding protein (CREB) signaling cascades. In a mouse traumatic brain injury (TBI) model, we found that systemic administration of 30 mg/kg NAS could improve hippocampal neurogenesis, manifested by the increased number of SOX-2-positive cells and increased expression of phosphorylated CREB in the dentate gyrus (DG) area. Treatment with NAS also ameliorates cognitive impairments caused by TBI, as assessed by Y-maze and contextual and cued fear conditioning tests. Taken together, these results provide valuable insights into the neuroprotective and neuroregenerative effects of NAS, suggesting it may have therapeutic potential for the treatment of TBI.

Open source code for behavior analysis in rodents

Aim

We have conducted a series of behavioral tests, which cover a broad range of behavioral domains, on various strains of genetically engineered mice. For the behavioral screening, we have been using Image J plugins that we developed for most of the tests in the battery. Our behavioral analysis system with the plugins enables systematic and automated image analysis of behavior. The plugins are freely available on the “Mouse Phenotype Database” website (http://www.mouse-phenotype.org/software.html). Here, we release the source code of the plugins in a Git repository with the aim of promoting their use and expanding their functionality.

Methods

We published the source code of the Image J plugins for behavioral analysis at Git repository (https://github.com/neuroinformatics). The source code for light/dark transition, elevated plus maze, open filed, T‐maze, and fear conditioning tests was made publicly available in the repository.

Conclusions

The source code of the plugins for the behavioral tests as well as the pre‐compiled binaries can be freely obtained. The open source code could promote the development and modification of the plugins for additional behavioral indices in these tests and for other behavioral tests.

We developed the Image J plugins for behavioral analysis, and the pre‐compiled plugins are freely available on the website of “Mouse Phenotype Database.” Here, we released the source code of the plugins in the Git repository.

Effects of chronic fentanyl administration on behavioral characteristics of mice

Background

Fentanyl, a synthetic opioid categorized as a narcotic analgesic, has a 100‐ to 200‐fold stronger effect than most opioids, such as morphine. Fatal accidents due to chronic use and abuse of fentanyl are a worldwide social problem. One reason for the abuse of fentanyl is its psychostimulant effects that could induce behavioral changes. The effects of chronic fentanyl administration on behavior, however, are unclear.

Methods

Adult male C57BL/6J mice were chronically administered fentanyl (0.03 or 0.3 mg/kg/d i.p.), and various behaviors were assessed using a behavioral test battery.

Results

Mice chronically administered a high dose of fentanyl (0.3 mg/kg/d) exhibited decreased anxiety‐like behavior as assessed by the open field and elevated plus maze tests. On the other hand, interruption of fentanyl administration led to increased anxiety‐like behavior as observed in the light and dark transition test. The hot plate test revealed that chronic administration of fentanyl reduced pain sensitivity. High‐dose chronic fentanyl administration reduced the locomotor stimulatory effects of cocaine. The results, however, failed to reach the threshold for study‐wide statistical significance.

Conclusion

Chronic fentanyl administration induces some behavioral changes in mice. Although further studies are needed to clarify the underlying mechanisms of the behavioral effects of chronic fentanyl administration, our findings suggest that fentanyl is safe under properly controlled conditions.

To investigate the effects of long‐term fentanyl use on brain function, adult male C57BL/6J mice were chronically administered fentanyl (0.03 or 0.3 mg/kg/d ip) and analyzed in a behavioral test battery. Chronic fentanyl administration reduced anxiety‐like behavior, pain sensitivity, and the locomotor stimulatory effects of cocaine in mice. The results, however, failed to reach the threshold for study‐wide statistical significance.

Distribution of Caskin1 protein and phenotypic characterization of its knockout mice using a comprehensive behavioral test battery

Calcium/calmodulin-dependent serine protein kinase (CASK)-interacting protein 1 (Caskin1) is a direct binding partner of the synaptic adaptor protein CASK. Because Caskin1 forms homo-multimers and binds not only CASK but also other neuronal proteins in vitro, it is anticipated to have neural functions; but its exact role in mammals remains unclear. Previously, we showed that the concentration of Caskin1 in the spinal dorsal horn increases under chronic pain. To characterize this protein, we generated Caskin1-knockout (Caskin1-KO) mice and specific anti-Caskin1 antibodies. Biochemical and immunohistochemical analyses demonstrated that Caskin1 was broadly distributed in the whole brain and spinal cord, and that it primarily localized at synapses. To elucidate the neural function of Caskin1 in vivo, we subjected Caskin1-KO mice to comprehensive behavioral analysis. The mutant mice exhibited differences in gait, enhanced nociception, and anxiety-like behavior relative to their wild-type littermates. In addition, the knockouts exhibited strong freezing responses, with or without a cue tone, in contextual and cued-fear conditioning tests as well as low memory retention in the Barnes Maze test. Taken together, these results suggest that Caskin1 contributes to a wide spectrum of behavioral phenotypes, including gait, nociception, memory, and stress response, in broad regions of the central nervous system.

MouBeAT: A New and Open Toolbox for Guided Analysis of Behavioral Tests in Mice

Animal behavioral tests are essential to understand the bases of neurologic and psychological disorders, which can be evaluated by different methodological and experimental models. However, the quantification of behavioral tests results is limited by the considerable amount of time needed for manual evaluation and the high costs of automated analysis software. To overcome these limitations, we describe here a new, open source toolbox for ImageJ, called Mouse Behavioral Analysis Toolbox (MouBeAT), designed to analyze different behavioral tests in rodents semi-automatically. These tests include Open Field (OF), Elevated Plus Maze (EPM), Y-maze (YM) test and Morris Water Maze (MWM). MouBeAT showed a high correlation with manual evaluation in all the parameters analyzed for all the behavioral tests, reinforcing its value as an accurate analysis tool. This new tool is freely available online.

Cognitive and emotional alterations in App knock-in mouse models of Aβ amyloidosis

Background

Alzheimer’s disease (AD), the most common cause of dementia, is characterized by the progressive deposition of amyloid-β (Aβ) peptides and neurofibrillary tangles. Mouse models of Aβ amyloidosis generated by knock-in (KI) of a humanized Aβ sequence provide distinct advantages over traditional transgenic models that rely on overexpression of amyloid precursor protein (APP). In App-KI mice, three familial AD-associated mutations were introduced into the endogenous mouse App locus to recapitulate Aβ pathology observed in AD: the Swedish (NL) mutation, which elevates total Aβ production; the Beyreuther/Iberian (F) mutation, which increases the Aβ42/Aβ40 ratio; and the Arctic (G) mutation, which promotes Aβ aggregation. App^NL-G-F mice harbor all three mutations and develop progressive Aβ amyloidosis and neuroinflammatory response in broader brain areas, whereas App^NL mice carrying only the Swedish mutation exhibit no overt AD-related pathological changes. To identify behavioral alterations associated with Aβ pathology, we assessed emotional and cognitive domains of App^NL-G-F and App^NL mice at different time points, using the elevated plus maze, contextual fear conditioning, and Barnes maze tasks.

Results

Assessments of emotional domains revealed that, in comparison with wild-type (WT) C57BL/6J mice, App^{NL-G-F/NL-G-F} mice exhibited anxiolytic-like behavior that was detectable from 6 months of age. By contrast, App^NL/NL mice exhibited anxiogenic-like behavior from 15 months of age. In the contextual fear conditioning task, both App^NL/NL and App^{NL-G-F/NL-G-F} mice exhibited intact learning and memory up to 15–18 months of age, whereas App^{NL-G-F/NL-G-F} mice exhibited hyper-reactivity to painful stimuli. In the Barnes maze task, App^{NL-G-F/NL-G-F} mice exhibited a subtle decline in spatial learning ability at 8 months of age, but retained normal memory functions.

Conclusion

App^NL/NL and App^{NL-G-F/NL-G-F} mice exhibit behavioral changes associated with non-cognitive, emotional domains before the onset of definitive cognitive deficits. Our observations consistently indicate that App^{NL-G-F/NL-G-F} mice represent a model for preclinical AD. These mice are useful for the study of AD prevention rather than treatment after neurodegeneration.

Electronic supplementary material

The online version of this article (10.1186/s12868-018-0446-8) contains supplementary material, which is available to authorized users.

Prefrontal cortex-dependent innate behaviors are altered by selective knockdown of Gad1 in neuropeptide Y interneurons

GABAergic dysfunction has been implicated in a variety of neurological and psychiatric disorders, including anxiety disorders. Anxiety disorders are the most common type of psychiatric disorder during adolescence. There is a deficiency of GABAergic transmission in anxiety, and enhancement of GABA transmission through pharmacological means reduces anxiety behaviors. GAD67—the enzyme responsible for GABA production–has been linked to anxiety disorders. One class of GABAergic interneurons, Neuropeptide Y (NPY) expressing cells, is abundantly found in brain regions associated with anxiety and fear learning, including prefrontal cortex, hippocampus and amygdala. Additionally, NPY itself has been shown to have anxiolytic effects, and loss of NPY+ interneurons enhances anxiety behaviors. A previous study showed that knockdown of Gad1 from NPY+ cells led to reduced anxiety behaviors in adult mice. However, the role of GABA release from NPY+ interneurons in adolescent anxiety is unclear. Here we used a transgenic mouse that reduces GAD67 in NPY+ cells (NPYGAD1-TG) through Gad1 knockdown and tested for effects on behavior in adolescent mice. Adolescent NPYGAD1-TG mice showed enhanced anxiety-like behavior and sex-dependent changes in locomotor activity. We also found enhancement in two other innate behavioral tasks, nesting construction and social dominance. In contrast, fear learning was unchanged. Because we saw changes in behavioral tasks dependent upon prefrontal cortex and hippocampus, we investigated the extent of GAD67 knockdown in these regions. Immunohistochemistry revealed a 40% decrease in GAD67 in NPY+ cells in prefrontal cortex, indicating a significant but incomplete knockdown of GAD67. In contrast, there was no decrease in GAD67 in NPY+ cells in hippocampus. Consistent with this, there was no change in inhibitory synaptic transmission in hippocampus. Our results show the behavioral impact of cell-specific interneuron dysfunction and suggest that GABA release by NPY+ cells is important for regulating innate prefrontal cortex-dependent behavior in adolescents.

Dissociated Role of D-Serine in Extinction During Consolidation vs. Reconsolidation of Context Conditioned Fear

Extinction-based exposure therapy is widely used for the treatment of anxiety disorders, such as post-traumatic stress disorder (PTSD). D-serine, an endogenous co-agonist at the glycine-binding site of the N-methyl-D-aspartate-type glutamate receptor (NMDAR), has been shown to be involved in extinction of fear memory. Recent findings suggest that the length of time between the initial learning and an extinction session is a determinant of neural mechanism involved in fear extinction. However, how D-serine is involved in extinction of fear memory at different timings remains unclear. In the present study, we investigated the role of D-serine in immediate, delayed and post-retrieval extinction (P-RE) of contextual fear memory using wild-type (WT) and serine racemase (SRR) knockout (KO) mice that exhibit 90% reduction in D-serine content in the hippocampus. We found that SRR disruption impairs P-RE, facilitates immediate extinction (IE), but has no effect on delayed extinction (DE) of contextual fear memories. The impaired P-RE of contextual fear memory in SRRKO mice was associated with increased expression of the GluA1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor (AMPAR) in the hippocampal synaptic membrane fraction after P-RE, and this increase of AMPAR and impaired P-RE were rescued by the administration of D-serine to SRRKO mice. Our findings suggest that D-serine is differentially involved in the regulation of contextual fear extinction depending on the timing of behavioral intervention, and that combining D-serine or other drugs, enhancing the NMDAR function, with P-RE may achieve optimal outcomes for the treatment of PTSD.

Comprehensive behavioral analysis of mice deficient in Rapgef2 and Rapgef6, a subfamily of guanine nucleotide exchange factors for Rap small GTPases possessing the Ras/Rap-associating domain

Rapgef2 and Rapgef6 define a subfamily of guanine nucleotide exchange factors for Rap small GTPases, characterized by the possession of the Ras/Rap-associating domain. Previous genomic analyses suggested their possible involvement in the etiology of schizophrenia. We recently demonstrated the development of an ectopic cortical mass (ECM), which resembles the human subcortical band heterotopia, in the dorsal telencephalon-specific Rapgef2 conditional knockout (Rapgef2-cKO) brains. Additional knockout of Rapgef6 in Rapgef2-cKO mice resulted in gross enlargement of the ECM whereas knockout of Rapgef6 alone (Rapgef6-KO) had no discernible effect on the brain morphology. Here, we performed a battery of behavioral tests to examine the effects of Rapgef2 or Rapgef6 deficiency on higher brain functions. Rapgef2-cKO mice exhibited hyperlocomotion phenotypes. They showed decreased anxiety-like behavior in the elevated plus maze and the open-field tests as well as increased depression-like behavior in the Porsolt forced swim and tail suspension tests. They also exhibited increased sociability especially in novel environments. They showed defects in cognitive function as evidenced by reduced learning ability in the Barnes circular maze test and by impaired working memory in the T maze tests. In contrast, although Rapgef6 and Rapgef2 share similarities in biochemical roles, Rapgef6-KO mice exhibited mild behavioral abnormalities detected with a number of behavioral tests, such as hyperlocomotion phenotype in the open-field test and the social interaction test with a novel environment and working-memory defects in the T-maze test. In conclusion, although there were differences in their brain morphology and the magnitude of the behavioral abnormalities, Rapgef2-cKO mice and Rapgef6-KO mice exhibited hyperlocomotion phenotype and working-memory defect, both of which could be recognized as schizophrenia-like behavior.

Comprehensive behavioral analysis of tryptophan 2,3-dioxygenase (Tdo2) knockout mice

AIMS

Tryptophan 2,3-dioxygenase (TDO2) is an initial rate-limiting enzyme of the kynurenine (Kyn) pathway in tryptophan (Trp) metabolism. The Trp-degrading enzymes, TDO2 and indoleamine 2,3-dioxygenase, are activated by stress and/or inflammation. Dysregulation of Trp metabolism, which causes shifts in the balance between Kyn and serotonin (5-HT) pathways, is associated with psychiatric and neurological disorders. In genetic studies, single-nucleotide polymorphisms in the TDO2 gene were shown to be involved in psychiatric disorders, such as schizophrenia and depression. It has been reported that targeted deletion of the Tdo2 gene in mice resulted in reduced anxiety-like behavior, enhanced exploratory activity and cognitive performance, and increased levels of Trp and 5-HT in the hippocampus and midbrain. However, the effect of Tdo2 gene deletion on behavioral phenotypes has not yet been investigated extensively.

MATERIALS & METHODS

We conducted tests to further examine the behavioral effects of knockout (KO) of Tdo2 in mice.

RESULTS

Deletion of Tdo2 resulted in seemingly lower anxiety-like behavior, higher locomotor activity, and abnormal gait pattern in mice, though none of them reached study-wide statistical significance. Tdo2 deficiency had no significant effects on other behaviors, such as prepulse inhibition, and depression-like and social behaviors.

DISCUSSION AND CONCLUSION

He lack of clear phenotypes in Tdo2KO mice in this study might be due to the absence of stress and inflammatory conditions, which could induce expression of Tdo2 mRNA. Further studies are necessary to elucidate the roles of Tdo2 in behavioral phenotypes related to psychiatric disorders.

Behavioral effects of long-term oral administration of aluminum ammonium sulfate in male and female C57BL/6J mice

Background

Aluminum (Al) is considered to be a neurotoxic metal, and excessive exposure to Al has been reported to be a potential risk factor for neurodegenerative diseases. Al ammonium sulfate is one of the Al compounds that is widely used as a food additive. However, the effects of the oral administration of Al ammonium sulfate on physical development and behavior remain to be examined.

Methods

In this study, we investigated the effects of the administration of Al ammonium sulfate 12‐water dissolved in drinking water (0.075 mg/mL) beginning in adolescence on various types of behavior in adult female C57BL/6J mice through a battery of behavioral tests (low‐dose experiment; Experiment 1). We further examined the behavioral effects of the oral administration of a higher dose of the Al compound in drinking water (1 mg/mL) beginning in the prenatal period on behavior in adult male and female mice (high‐dose experiment; Experiment 2).

Results

In the low‐dose experiment, in which females’ oral intake of Al was estimated to be 0.97 mg Al/kg/d as adults, Al‐treated females exhibited an increase in total arm entries in the elevated plus maze test, an initial decrease and subsequent increase in immobility in the forced swim test, and reduced freezing in the fear conditioning test approximately 1 month after the conditioning session compared with vehicle‐treated females (uncorrected P < .05). However, the behavioral differences did not reach a statistically significant level after correction for multiple testing. In the high‐dose experiment, in which animals’ oral intakes were estimated to be about ten times higher than those in the low‐dose experiment, behavioral differences found in the low‐dose experiment were not observed in high‐dose Al‐treated mice, suggesting that the results of the low‐dose experiment might be false positives. Additionally, although high‐dose Al‐treated females exhibited increased social contacts with unfamiliar conspecifics and impaired reference memory performance, and high‐dose Al‐treated mice exhibited decreases in prepulse inhibition and in correct responses in the working memory task (uncorrected P < .05), the differences in any of the behavioral measures did not reach the significance level after correction for multiple testing.

Conclusion

Our results show that long‐term oral exposure to Al ammonium sulfate at the doses used in this study may have the potential to induce some behavioral changes in C57BL/6J mice. However, the behavioral effects of Al were small and statistically weak, as indicated by the fact that the results failed to reach the study‐wide significance level. Thus, further study will be needed to replicate the results and reevaluate the behavioral outcomes of oral intake of Al ammonium sulfate.

Aluminum (Al) ammonium sulfate was orally administered to C57BL/6J mice (estimated dose of 0.97‐9.78 Al mg/kg/d). Behavioral effects of Al were assessed in a battery of behavioral tests in mice in adulthood. Statistically significant behavioral differences were not found between Al‐ and vehicle‐treated mice.

Acute inhalation of combustion smoke triggers neuroinflammation and persistent anxiety-like behavior in the mouse

CONTEXT

Acute inhalation of combustion smoke triggers neurologic sequelae in survivors. Due to the challenges posed by heterogeneity of smoke exposures in humans, mechanistic links between acute smoke inhalation and neuropathologic sequelae have not been systematically investigated.

METHODS

Here, using mouse model of acute inhalation of combustion smoke, we studied longitudinal neurobehavioral manifestations of smoke exposures and molecular/cellular changes in the mouse brain.

RESULTS

Immunohistochemical analyses at eight months post-smoke, revealed hippocampal astrogliosis and microgliosis accompanied by reduced myelination. Elevated expression of proinflammatory cytokines was also detected. Longitudinal testing in different neurobehavioral paradigms in the course of post-smoke recovery, revealed lasting anxiety-like behavior. The examined paradigms included the open field exploration/anxiety testing at two, four and six months post-smoke, which detected decreases in total distance traveled and time spent in the central arena in the smoke-exposed compared to sham-control mice, suggestive of dampened exploratory activity and increased anxiety-like behavior. In agreement with reduced open field activity, cued fear conditioning test revealed increased freezing in response to conditioned auditory stimulus in mice after acute smoke inhalation. Similarly, elevated plus maze testing demonstrated lesser presence in open arms of the maze, consistent with anxiety-like behavior, for the post-smoke exposure mice.

CONCLUSIONS

Taken together, our data demonstrate for the first time persistent neurobehavioral manifestations of acute inhalation of combustion smoke and provide new insights into long-term progression of events initiated by disrupted brain oxygenation that might contribute to lasting adverse sequelae in survivors of smoke inhalation injuries.

Elevation of arachidonoylethanolamide levels by activation of the endocannabinoid system protects against colitis and ameliorates remote organ lesions in mice

The endocannabinoid system (ECS) is a potential pharmaceutical target for the treatment of inflammatory bowel diseases (IBDs). The aim of this study was to explore the effects of activation of the ECS on IBD and the associated neural inflammation-induced disruption of the blood-brain barrier (BBB). In a mouse model of trinitrobenzene sulfonic acid-induced colitis, the inhibition of fatty acid amide hydrolase with URB597 elevated the arachidonoylethanolamide concentration of the colon. Macroscopic alterations of the colons were evaluated, and the 7-day survival rate of mice was analyzed. BBB integrity was assessed using a dye tracer method, and the cognitive function of mice was examined using a fear-conditioning test. URB597 treatment significantly reduced macroscopic alterations of the colon, decreased the mortality rate, and protected the integrity of the BBB in the mice (P<0.05). No significant changes were observed in the cognitive functions of the mice (P>0.05); therefore, the neuroprotective effect of ECS in this colitis model requires further investigation. Activation of the ECS was efficient in ameliorating colitis and increasing the survival rate of the mice, and reducing remote organ changes induced by colitis. The results suggest that modulation of the ECS is a potential therapeutic approach for IBDs and the associated remote organ lesions.

Predator Odor-induced Freezing Test for Mice

The innate fear response is an emotional response that does not require any previously acquired conditioning. One of the standard methods to analyze the innate fear response is a 2,4,5-trimethylthiazoline (TMT)-induced freezing test. TMT is an odor originally isolated from anal secretion of the red fox. Acute TMT exposure has been shown to induce robust freezing behavior in rats and mice (Wallace and Rosen, 2000; Galliot et al., 2012 ). Here, I show how to expose mice to TMT and how to analyze their freezing behavior.

Arid1b Haploinsufficiency Causes Abnormal Brain Gene Expression and Autism-Related Behaviors in Mice

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with core symptoms that include poor social communication, restricted interests, and repetitive behaviors. Several ASD mouse models exhibit impaired social interaction, anxiety-like behavior, and elevated perseveration. Large-scale whole exome sequencing studies identified many genes putatively associated with ASD. Like chromodomain helicase DNA binding protein 8 (CHD8), the most frequently mutated gene in individuals with ASD, the candidate gene AT-rich interaction domain 1B (ARID1B) encodes a chromatin remodeling factor. Arid1b heterozygous knockout (hKO) mice exhibited ASD-like traits related to social behavior, anxiety, and perseveration, in addition to associated features reported in some cases of ASD, such as reduced weight, impaired motor coordination, and hydrocephalus. Hydrocephalus was present in 5 of 91 hKO mice, while it was not observed in wild-type littermates (0 of 188). Genome-wide gene expression patterns in Arid1b hKO mice were similar to those in ASD patients and Chd8-haploinsufficient mice, an ASD model, and to developmental changes in gene expression in fast-spiking cells in the mouse brain. Our results suggest that Arid1b haploinsufficiency causes ASD-like phenotypes in mice.

Strain-dependence of the Angelman Syndrome phenotypes in Ube3a maternal deficiency mice

Angelman syndrome (AS) is a genetic neurodevelopmental disorder, most commonly caused by deletion or mutation of the maternal allele of the UBE3A gene, with behavioral phenotypes and seizures as key features. Currently no treatment is available, and therapeutics are often ineffective in controlling AS-associated seizures. Previous publications using the Ube3a maternal deletion model have shown behavioral and seizure susceptibility phenotypes, however findings have been variable and merit characterization of electroencephalographic (EEG) activity. In this study, we extend previous studies comparing the effect of genetic background on the AS phenotype by investigating the behavioral profile, EEG activity, and seizure threshold. AS C57BL/6J mice displayed robust behavioral impairments, spontaneous EEG polyspikes, and increased cortical and hippocampal power primarily driven by delta and theta frequencies. AS 129 mice performed poorly on wire hang and contextual fear conditioning and exhibited a lower seizure threshold and altered spectral power. AS F1 hybrid mice (C57BL/6J × 129) showed milder behavioral impairments, infrequent EEG polyspikes, and fewer spectral power alterations. These findings indicate the effect of common genetic backgrounds on the Ube3a maternal deletion behavioral, EEG, and seizure threshold phenotypes. Our results will inform future studies on the optimal strain for evaluating therapeutics with different AS-like phenotypes.

Comprehensive Behavioral Analysis of Activating Transcription Factor 5-Deficient Mice

Activating transcription factor 5 (ATF5) is a member of the CREB/ATF family of basic leucine zipper transcription factors. We previously reported that ATF5-deficient (ATF5^-/-) mice demonstrated abnormal olfactory bulb development due to impaired interneuron supply. Furthermore, ATF5^-/- mice were less aggressive than ATF5^+/+ mice. Although ATF5 is widely expressed in the brain, and involved in the regulation of proliferation and development of neurons, the physiological role of ATF5 in the higher brain remains unknown. Our objective was to investigate the physiological role of ATF5 in the higher brain. We performed a comprehensive behavioral analysis using ATF5^-/- mice and wild type littermates. ATF5^-/- mice exhibited abnormal locomotor activity in the open field test. They also exhibited abnormal anxiety-like behavior in the light/dark transition test and open field test. Furthermore, ATF5^-/- mice displayed reduced social interaction in the Crawley’s social interaction test and increased pain sensitivity in the hot plate test compared with wild type. Finally, behavioral flexibility was reduced in the T-maze test in ATF5^-/- mice compared with wild type. In addition, we demonstrated that ATF5^-/- mice display disturbances of monoamine neurotransmitter levels in several brain regions. These results indicate that ATF5 deficiency elicits abnormal behaviors and the disturbance of monoamine neurotransmitter levels in the brain. The behavioral abnormalities of ATF5^-/- mice may be due to the disturbance of monoamine levels. Taken together, these findings suggest that ATF5^-/- mice may be a unique animal model of some psychiatric disorders.

Decreased cohesin in the brain leads to defective synapse development and anxiety-related behavior

Abnormal epigenetic regulation can cause the nervous system to develop abnormally. Here, we sought to understand the mechanism by which this occurs by investigating the protein complex cohesin, which is considered to regulate gene expression and, when defective, is associated with higher-level brain dysfunction and the developmental disorder Cornelia de Lange syndrome (CdLS). We generated conditional Smc3-knockout mice and observed greater dendritic complexity and larger numbers of immature synapses in the cerebral cortex of Smc3+/- mice. Smc3+/- mice also exhibited more anxiety-related behavior, which is a symptom of CdLS. Further, a gene ontology analysis after RNA-sequencing suggested the enrichment of immune processes, particularly the response to interferons, in the Smc3+/- mice. Indeed, fewer synapses formed in their cortical neurons, and this phenotype was rescued by STAT1 knockdown. Thus, low levels of cohesin expression in the developing brain lead to changes in gene expression that in turn lead to a specific and abnormal neuronal and behavioral phenotype.

Precondition of right frontal region with anodal tDCS can restore the fear memory impairment induced by ACPA in male mice

Fear memory and learning cause behavioural patterns such as fight or flight responses, which increase survival probability, but unfit processing of fear memory and learning can lead to maladaptive behaviours and maladies such as phobias, Post-Traumatic Stress Disorder (PTSD) and anxiety disorders. The growing prevalence of these maladies shows the need to quest novel methods for their treatment. We used anodal transcranial direct current stimulation (tDCS) on the right frontal region as a precondition neuromodulator and arachidonylcyclopropylamide (ACPA), a selective CB1 cannabinoid receptor agonist, as a fear memory impairing agent to assess their effects on contextual and auditory fear conditioning (reliable model for fear studies). Right frontal anodal tDCS (0.2 mA for. 20 minutes) 24 hours before the train did not alter contextual and auditory learning and memory in short-term (24 hrs after the training phase). Moreover, intraperitoneal pre-train injection of ACPA (0.1 mg/kg) alone, decreased both contextual and auditory learning and memory in short- but not long-term. Right frontal anodal tDCS improved short-term contextual fear memory in subthreshold doses of ACPA. On the other hand, right frontal anodal tDCS in long-term improved (lower doses of ACPA) and restored (higher doses of ACPA) both fear memories. These findings showed that, aforementioned approach could cause durable learning and memory improvements. Also this combined modality could be useful for fear extinction training and maladies which inflict amnesia.

DREADD in parvalbumin interneurons of the dentate gyrus modulates anxiety, social interaction and memory extinction

Parvalbumin (PV)-positive interneurons in the hippocampus play a critical role in animal memory, such as spatial working memory. However, how PV-positive interneurons in the subregions of the hippocampus affect animal behaviors remains poorly defined. Here, we achieved specific and reversible activation of PV-positive interneurons using designer receptors exclusively activated by designer drugs (DREADD) technology. Inducible DREADD expression was demonstrated in vitro in cultured neurons, in which co-transfection of the hM3D-Gq-mCherry vector with a Cre plasmid resulted in a cellular response to hM3Dq ligand clozapine-N-oxide (CNO) stimulation. In addition, the dentate gyrus (DG) of PV-Cre mice received bilateral injection of control lentivirus or lentivirus expressing double floxed hM3D-Gq-mCherry. Selective activation of PV-positive interneurons in the DG did not affect locomotor activity or depression-related behavior in mice. Interestingly, stimulation of PV-positive interneurons induced an anxiolytic effect. Activation of PVpositive interneurons appears to impair social interaction to novelty, but has no effect on social motivation. However, this defect is likely due to the anxiolytic effect as the exploratory behavior of mice expressing hM3DGq is significantly increased. Mice expressing hM3D-Gq did not affect novel object recognition. Activation of PV-positive interneurons in the DG maintains intact cued and contextual fear memory but facilitates fear extinction. Collectively, our results demonstrated that proper control of PV interneurons activity in the DG is critical for regulation of the anxiety, social interaction and fear extinction. These results improve our fundamental understanding of the physiological role of PV-positive interneurons in the hippocampus.

Modulation of cannabinoid signaling by hippocampal 5-HT4 serotonergic system in fear conditioning

Behavioral studies have suggested a key role for the cannabinoid system in the modulation of conditioned fear memory. Likewise, much of the literature has revealed that the serotonergic system affects Pavlovian fear conditioning and extinction. A high level of functional overlap between the serotonin and cannabinoid systems has also been reported. To clarify the interaction between the hippocampal serotonin (5-HT4) receptor and the cannabinoid CB1 receptor in the acquisition of fear memory, the effects of 5-HT4 agents, arachidonylcyclopropylamide (ACPA; CB1 receptor agonist), and the combined use of these drugs on fear learning were studied in a fear conditioning task in adult male NMRI mice. Pre-training intraperitoneal administration of ACPA (0.1 mg/kg) decreased the percentage of freezing time in both context- and tone-dependent fear conditions, suggesting impairment of the acquisition of fear memory. Pre-training, intra-hippocampal (CA1) microinjection of RS67333, a 5-HT4 receptor agonist, at doses of 0.1 and 0.2 or 0.2 µg/mouse impaired contextual and tone fear memory, respectively. A subthreshold dose of RS67333 (0.005 µg/mouse) did not alter the ACPA response in either condition. Moreover, intra-CA1 microinjection of RS23597 as a 5-HT4 receptor antagonist did not alter context-dependent fear memory acquisition, but it did impair tone-dependent fear memory acquisition. However, a subthreshold dose of the RS23597 (0.01 µg/mouse) potentiated ACPA-induced fear memory impairment in both conditions. Therefore, we suggest that the blockade of hippocampal 5-HT4 serotonergic system modulates cannabinoid signaling induced by the activation of CB1 receptors in conditioned fear.

Comprehensive behavioral phenotyping of a new Semaphorin 3 F mutant mouse

BACKGROUND

Semaphorin 3 F (Sema3F) is a secreted type of the Semaphorin family of axon guidance molecules. Sema3F and its receptor neuropilin-2 (Npn-2) are expressed in a mutually exclusive manner in the embryonic mouse brain regions including olfactory bulb, hippocampus, and cerebral cortex. Sema3F is thought to have physiological functions in the formation of neuronal circuitry and its refinement. However, functional roles of Sema3F in the brain remain to be clarified. Here, we examined behavioral effects of Sema3F deficiency through a comprehensive behavioral test battery in Sema3F knockout (KO) male mice to understand the possible functions of Sema3F in the brain.

RESULTS

Male Sema3F KO and wild-type (WT) control mice were subjected to a battery of behavioral tests, including neurological screen, rotarod, hot plate, prepulse inhibition, light/dark transition, open field, elevated plus maze, social interaction, Porsolt forced swim, tail suspension, Barnes maze, and fear conditioning tests. In the open field test, Sema3F KO mice traveled shorter distance and spent less time in the center of the field than WT controls during the early testing period. In the light/dark transition test, Sema3F KO mice also exhibited decreased distance traveled, fewer number of transitions, and longer latency to enter the light chamber compared with WT mice. In addition, Sema3F KO mice traveled shorter distance than WT mice in the elevated plus maze test, although there were no differences between genotypes in open arm entries and time spent in open arms. Similarly, Sema3F KO mice showed decreased distance traveled in the social interaction test. Sema3F KO mice displayed reduced immobility in the Porsolt forced swim test whereas there was no difference in immobility between genotypes in the tail suspension test. In the fear conditioning test, Sema3F KO mice exhibited increased freezing behavior when exposed to a conditioning context and an altered context in absence of a conditioned stimulus. In the tests for assessing motor function, pain sensitivity, startle response to an acoustic stimulus, sensorimotor gating, or spatial reference memory, there were no significant behavioral differences between Sema3F KO and WT mice.

CONCLUSIONS

These results suggest that Sema3F deficiency induces decreased locomotor activity and possibly abnormal anxiety-related behaviors and also enhances contextual memory and generalized fear in mice. Thus, our findings suggest that Sema3F plays important roles in the development of neuronal circuitry underlying the regulation of some aspects of anxiety and fear responses.

Age-related changes in behavior in C57BL/6J mice from young adulthood to middle age

Background

Aging is considered to be associated with progressive changes in the brain and its associated sensory, motor, and cognitive functions. A large number of studies comparing young and aged animals have reported differences in various behaviors between age-cohorts, indicating behavioral dysfunctions related to aging. However, relatively little is known about behavioral changes from young adulthood to middle age, and the effect of age on behavior during the early stages of life remains to be understood. In order to investigate age-related changes in the behaviors of mice from young adulthood to middle age, we performed a large-scale analysis of the behavioral data obtained from our behavioral test battery involving 1739 C57BL/6J wild-type mice at 2–12 months of age.

Results

Significant behavioral differences between age groups (2–3-, 4–5-, 6–7-, and 8–12-month-old groups) were found in all the behavioral tests, including the light/dark transition, open field, elevated plus maze, rotarod, social interaction, prepulse inhibition, Porsolt forced swim, tail suspension, Barnes maze, and fear conditioning tests, except for the hot plate test. Compared with the 2–3-month-old group, the 4–5- and 6–7-month-old groups exhibited decreased locomotor activity to novel environments, motor function, acoustic startle response, social behavior, and depression-related behavior, increased prepulse inhibition, and deficits in spatial and cued fear memory. For most behaviors, the 8–12-month-old group showed similar but more pronounced changes in most of these behaviors compared with the younger age groups. Older groups exhibited increased anxiety-like behavior in the light/dark transition test whereas those groups showed seemingly decreased anxiety-like behavior measured by the elevated plus maze test.

Conclusions

The large-scale analysis of behavioral data from our battery of behavioral tests indicated age-related changes in a wide range of behaviors from young adulthood to middle age in C57BL/6J mice, though these results might have been influenced by possible confounding factors such as the time of day at testing and prior test experience. Our results also indicate that relatively narrow age differences can produce significant behavioral differences during adulthood in mice. These findings provide an insight into our understanding of the neurobiological processes underlying brain function and behavior that are subject to age-related changes in early to middle life. The findings also indicate that age is one of the critical factors to be carefully considered when designing behavioral tests and interpreting behavioral differences that might be induced by experimental manipulations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-016-0191-9) contains supplementary material, which is available to authorized users.

NMDA receptor agonists reverse impaired psychomotor and cognitive functions associated with hippocampal Hbegf-deficiency in mice

BACKGROUND

Structural and functional changes of the hippocampus are correlated with psychiatric disorders and cognitive dysfunctions. Genetic deletion of heparin-binding epidermal growth factor-like growth factor (HB-EGF), which is predominantly expressed in cortex and hippocampus, also causes similar psychiatric and cognitive dysfunctions, accompanying down-regulated NMDA receptor signaling. However, little is known of such dysfunctions in hippocampus-specific Hbegf cKO mice.

RESULTS

We successfully developed hippocampus-specific cKO mice by crossbreeding floxed Hbegf and Gng7-Cre knock-in mice, as Gng7 promoter-driven Cre is highly expressed in hippocampal neurons as well as striatal medium spiny neurons. In mice lacking hippocampus Hbegf gene, there was a decreased neurogenesis in the subgranular zone (SGZ) of the dentate gyrus as well as down-regulation of PSD-95/NMDA-receptor-NR1/NR2B subunits and related NMDA receptor signaling. Psychiatric, social-behavioral and cognitive abnormalities were also observed in hippocampal cKO mice. Interestingly, D-cycloserine and nefiracetam, positive allosteric modulators (PAMs) of NMDA receptor reversed the apparent reduction in NMDA receptor signaling and most behavioral abnormalities. Furthermore, decreased SGZ neurogenesis in hippocampal cKO mice was reversed by nefiracetam.

CONCLUSIONS

The present study demonstrates that PAMs of NMDA receptor have pharmacotherapeutic potentials to reverse down-regulated NMDA receptor signaling, neuro-socio-cognitive abnormalities and decreased neurogenesis in hippocampal cKO mice.

Comprehensive behavioral analysis of voltage-gated calcium channel beta-anchoring and -regulatory protein knockout mice

Calcium (Ca²⁺) influx through voltage-gated Ca²⁺ channels (VGCCs) induces numerous intracellular events such as neuronal excitability, neurotransmitter release, synaptic plasticity, and gene regulation. It has been shown that genes related to Ca²⁺ signaling, such as the CACNA1C, CACNB2, and CACNA1I genes that encode VGCC subunits, are associated with schizophrenia and other psychiatric disorders. Recently, VGCC beta-anchoring and -regulatory protein (BARP) was identified as a novel regulator of VGCC activity via the interaction of VGCC β subunits. To examine the role of the BARP in higher brain functions, we generated BARP knockout (KO) mice and conducted a comprehensive battery of behavioral tests. BARP KO mice exhibited greatly reduced locomotor activity, as evidenced by decreased vertical activity, stereotypic counts in the open field test, and activity level in the home cage, and longer latency to complete a session in spontaneous T-maze alteration test, which reached “study-wide significance.” Acoustic startle response was also reduced in the mutants. Interestingly, they showed multiple behavioral phenotypes that are seemingly opposite to those seen in the mouse models of schizophrenia and its related disorders, including increased working memory, flexibility, prepulse inhibition, and social interaction, and decreased locomotor activity, though many of these phenotypes are statistically weak and require further replications. These results demonstrate that BARP is involved in the regulation of locomotor activity and, possibly, emotionality. The possibility was also suggested that BARP KO mice may serve as a unique tool for investigating the pathogenesis/pathophysiology of schizophrenia and related disorders. Further evaluation of the molecular and physiological phenotypes of the mutant mice would provide new insights into the role of BARP in higher brain functions.

IL1RAPL1 knockout mice show spine density decrease, learning deficiency, hyperactivity and reduced anxiety-like behaviours

IL-1 receptor accessory protein-like 1 (IL1RAPL1) is responsible for nonsyndromic intellectual disability and is associated with autism. IL1RAPL1 mediates excitatory synapse formation through trans-synaptic interaction with PTPδ. Here, we showed that the spine density of cortical neurons was significantly reduced in IL1RAPL1 knockout mice. The spatial reference and working memories and remote fear memory were mildly impaired in IL1RAPL1 knockout mice. Furthermore, the behavioural flexibility was slightly reduced in the T-maze test. Interestingly, the performance of IL1RAPL1 knockout mice in the rotarod test was significantly better than that of wild-type mice. Moreover, IL1RAPL1 knockout mice consistently exhibited high locomotor activity in all the tasks examined. In addition, open-space and height anxiety-like behaviours were decreased in IL1RAPL1 knockout mice. These results suggest that IL1RAPL1 ablation resulted in spine density decrease and affected not only learning but also behavioural flexibility, locomotor activity and anxiety.

Parameter optimization for automated behavior assessment: plug-and-play or trial-and-error?

Behavioral neuroscience is relying more and more on automated behavior assessment, which is often more time-efficient and objective than manual scoring by a human observer. However, parameter adjustment and calibration are a trial-and-error process that requires careful fine-tuning in order to obtain reliable software scores in each context configuration. In this paper, we will pinpoint some caveats regarding the choice of parameters, and give an overview of our own and other researchers' experience with widely used behavioral assessment software. We conclude that, although each researcher should weigh the pros and cons of relying on software vs. manual scoring, we should be aware of possible divergence between both scores, which might be especially relevant when dealing with subtle behavioral effects, like for example in generalization or genetic research.