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The maturation of photon-counting detector (PCD) technology promises to enhance routine CT imaging applications with high-fidelity spectral information. In this paper, we demonstrate the power of this synergy and our complementary reconstruction techniques, performing 4D, cardiac PCD-CT data acquisition and reconstruction in a mouse model of atherosclerosis, including calcified plaque. Specifically, in vivo cardiac micro-CT scans were performed in four ApoE knockout mice, following their development of calcified plaques. The scans were performed with a prototype PCD (DECTRIS, Ltd.) with 4 energy thresholds. Projections were sampled every 10 ms with a 10 ms exposure, allowing the reconstruction of 10 cardiac phases at each of 4 energies (40 total 3D volumes per mouse scan). Reconstruction was performed iteratively using the split Bregman method with constraints on spectral rank and spatio-temporal gradient sparsity. The reconstructed images represent the first in vivo, 4D PCD-CT data in a mouse model of atherosclerosis. Robust regularization during iterative reconstruction yields high-fidelity results: an 8-fold reduction in noise standard deviation for the highest energy threshold (relative to unregularized algebraic reconstruction), while absolute spectral bias measurements remain below 13 Hounsfield units across all energy thresholds and scans. Qualitatively, image domain material decomposition results show clear separation of iodinated contrast and soft tissue from calcified plaque in the in vivo data. Quantitatively, spatial, spectral, and temporal fidelity are verified through a water phantom scan and a realistic MOBY phantom simulation experiment: spatial resolution is robustly preserved by iterative reconstruction (10% MTF: 2.8–3.0 lp/mm), left-ventricle, cardiac functional metrics can be measured from iodine map segmentations with ~1% error, and small calcifications (615 μm) can be detected during slow moving phases of the cardiac cycle. Given these preliminary results, we believe that PCD technology will enhance dynamic CT imaging applications with high-fidelity spectral and material information. [ABSTRACT FROM AUTHOR]

Longitudinal studies of bone adaptation in mice using in vivo micro-computed tomography (μCT) have been commonly used for pre-clinical evaluation of physical and pharmacological interventions. The main advantage of this approach is to use each mouse as its own control, reducing considerably the sample size required by statistical power analysis. To date, multi-scale estimation of bone adaptations become essential since the bone activity that takes place at different scales may be associated with different bone mechanisms. Measures of bone adaptations at different time scales have been attempted in a previous study. This paper extends quantification of bone activity at different spatial scales with a proposition of a novel framework. The method involves applying level-set method (LSM) to track the geometric changes from the longitudinal in vivo μCT scans of mice tibia. Bone low- and high-spatial frequency patterns are then estimated using multi-resolution analysis. The accuracy of the framework is quantified by applying it to two times separated scanned images with synthetically manipulated global and/or local activity. The Root Mean Square Deviation (RMSD) was approximately 1.5 voxels or 0.7 voxels for the global low-spatial frequency or local high-spatial frequency changes, respectively. The framework is further applied to the study of bone changes in longitudinal datasets of wild-type mice tibiae over time and space. The results demonstrate the ability for the spatio-temporal quantification and visualisation of bone activity at different spatial scales in longitudinal studies thus providing further insight into bone adaptation mechanisms. [ABSTRACT FROM AUTHOR]

This paper presents a variational framework for dense diffeomorphic atlas-mapping onto high-throughput histology stacks at the 20 μm meso-scale. The observed sections are modelled as Gaussian random fields conditioned on a sequence of unknown section by section rigid motions and unknown diffeomorphic transformation of a three-dimensional atlas. To regularize over the high-dimensionality of our parameter space (which is a product space of the rigid motion dimensions and the diffeomorphism dimensions), the histology stacks are modelled as arising from a first order Sobolev space smoothness prior. We show that the joint maximum a-posteriori, penalized-likelihood estimator of our high dimensional parameter space emerges as a joint optimization interleaving rigid motion estimation for histology restacking and large deformation diffeomorphic metric mapping to atlas coordinates. We show that joint optimization in this parameter space solves the classical curvature non-identifiability of the histology stacking problem. The algorithms are demonstrated on a collection of whole-brain histological image stacks from the Mouse Brain Architecture Project. [ABSTRACT FROM AUTHOR]

Arousals can be roughly characterized by punctual intrusions of wakefulness into sleep. In a standard perspective, using human electroencephalography (EEG) data, arousals are associated to slow-wave rhythms and K-complex brain activity. The physiological mechanisms that give rise to arousals during sleep are not yet fully understood. Moreover, subtle body movement patterns, which may characterize arousals both in human and in animals, are usually not detectable by eye perception and are not in general present in sleep studies. In this paper, we focus attention on accelerometer records (AR) to characterize and predict arousal during slow wave sleep (SWS) stage of mice. Furthermore, we recorded the local field potentials (LFP) from the CA1 region in the hippocampus and paired with accelerometer data. The hippocampus signal was also used here to identify the SWS stage. We analyzed the AR dynamics of consecutive arousals using recurrence technique and the determinism (DET) quantifier. Recurrence is a fundamental property of dynamical systems, which can be exploited to characterize time series properties. The DET index evaluates how similar are the evolution of close trajectories: in this sense, it computes how accurate are predictions based on past trajectories. For all analyzed mice in this work, we observed, for the first time, the occurrence of a universal dynamic pattern a few seconds that precedes the arousals during SWS sleep stage based only on the AR signal. The predictability success of an arousal using DET from AR is nearly 90%, while similar analysis using LFP of hippocampus brain region reveal 88% of success. Noteworthy, our findings suggest an unique dynamical behavior pattern preceding an arousal of AR data during sleep. Thus, the employment of this technique applied to AR data may provide useful information about the dynamics of neuronal activities that control sleep-waking switch during SWS sleep period. We argue that the predictability of arousals observed through DET(AR) can be functionally explained by a respiratory-driven modification of neural states. Finally, we believe that the method associating AR data with other physiologic events such as neural rhythms can become an accurate, convenient and non-invasive way of studying the physiology and physiopathology of movement and respiratory processes during sleep. [ABSTRACT FROM AUTHOR]

With the development of hybrid imaging scanners, micro-CT is widely used in locating abnormalities, studying drug metabolism, and providing structural priors to aid image reconstruction in functional imaging. Due to the low contrast of soft tissues, segmentation of soft tissue organs from mouse micro-CT images is a challenging problem. In this paper, we propose a mouse segmentation scheme based on dynamic contrast enhanced micro-CT images. With a homemade fast scanning micro-CT scanner, dynamic contrast enhanced images were acquired before and after injection of non-ionic iodinated contrast agents (iohexol). Then the feature vector of each voxel was extracted from the signal intensities at different time points. Based on these features, the heart, liver, spleen, lung, and kidney could be classified into different categories and extracted from separate categories by morphological processing. The bone structure was segmented using a thresholding method. Our method was validated on seven BALB/c mice using two different classifiers: a support vector machine classifier with a radial basis function kernel and a random forest classifier. The results were compared to manual segmentation, and the performance was assessed using the Dice similarity coefficient, false positive ratio, and false negative ratio. The results showed high accuracy with the Dice similarity coefficient ranging from 0.709 ± 0.078 for the spleen to 0.929 ± 0.006 for the kidney. [ABSTRACT FROM AUTHOR]

Congenital nystagmus, involuntary oscillating small eye movements, is commonly thought to originate from aberrant interactions between brainstem nuclei and foveal cortical pathways. Here, we investigated whether nystagmus associated with congenital stationary night blindness (CSNB) results from primary deficits in the retina. We found that CSNB patients as well as an animal model (nob mice), both of which lacked functional nyctalopin protein (NYX, nyx) in ON bipolar cells (BCs) at their synapse with photoreceptors, showed oscillating eye movements at a frequency of 4–7 Hz. nob ON direction-selective ganglion cells (DSGCs), which detect global motion and project to the accessory optic system (AOS), oscillated with the same frequency as their eyes. In the dark, individual ganglion cells (GCs) oscillated asynchronously, but their oscillations became synchronized by light stimulation. Likewise, both patient and nob mice oscillating eye movements were only present in the light when contrast was present. Retinal pharmacological and genetic manipulations that blocked nob GC oscillations also eliminated their oscillating eye movements, and retinal pharmacological manipulations that reduced the oscillation frequency of nob GCs also reduced the oscillation frequency of their eye movements. We conclude that, in nob mice, synchronized oscillations of retinal GCs, most likely the ON-DCGCs, cause nystagmus with properties similar to those associated with CSNB in humans. These results show that the nob mouse is the first animal model for a form of congenital nystagmus, paving the way for development of therapeutic strategies. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH), a commonly abused drug, elevates extracellular dopamine (DA) levels by inducing DA efflux through the DA transporter (DAT). Emerging evidence in rodent models suggests that locomotor responses to a novel inescapable open field may predict behavioral responses to abused drugs; METH produces more potent stimulant effects in high responders to novelty than in low responders. We herein found that mice deficient in protein tyrosine phosphatase receptor type Z (Ptprz-KO) exhibited an enhanced behavioral response to novelty; however, METH-induced hyperlocomotion was significantly lower in Ptprz-KO than in wild-type mice when METH was administered at a non-toxic dose of 1 mg per kg body weight (bdw). Single-cell RT-PCR revealed that the majority of midbrain DA neurons expressed PTPRZ. No histological alterations were observed in the mesolimbic or nigrostriatal dopaminergic pathways in Ptprz-KO brains; however, a significant decrease was noted in brain DA turnover, suggesting functional alterations. In vivo microdialysis experiments revealed that METH-evoked DA release in the nucleus accumbens was significantly lower in Ptprz-KO mice than in wild-type mice. Consistent with this result, Ptprz-KO mice showed significantly fewer cell surface DAT as well as weaker DA uptake activity in striatal synaptosomes prepared 1 hr after the administration of METH than wild-type mice, while no significant differences were observed in the two groups treated with saline. These results indicate that the high response phenotype of Ptprz-KO mice to novelty may not be simply attributed to hyper-dopaminergic activity, and that deficits in PTPRZ reduce the effects of METH by reducing DAT activity. [ABSTRACT FROM AUTHOR]

Protein tyrosine phosphatase receptor type Z (PTPRZ) is preferentially expressed in the central nervous system as two transmembrane receptor isoforms PTPRZ-A/B and one secretory isoform PTPRZ-S. Ptprz-knockout mice lacking the expression of all three isoforms show behavioral, learning, and neurological abnormalities, including increased exploratory activities to novelty, deficits in spatial and contextual learning, and reduced responses to methamphetamine, relative to wild-type mice. To investigate whether PTPRZ isoforms play distinct physiological roles, we herein performed behavioral studies on two knock-in mouse lines: One expresses the catalytically inactive Cys-1930 to Ser (CS) mutants of PTPRZ-A/B, while the other generated in the present study expresses catalytically active mutants of PTPRZ-A/B lacking the negative regulatory PTP-D2 domain and C-terminal PDZ-binding motif (ΔD2) instead of wild-type PTPRZ-A/-B. In contrast to Ptprz-knockout mice, neither increased responses to novelty in the open field nor memory impairments in the inhibitory-avoidance task were observed in Ptprz-CS or Ptprz-ΔD2 mice. However, the effects of methamphetamine on locomotor activity were significantly weaker in Ptprz-KO mice and CS mutant mice than in wild-type mice, but were normal in ΔD2 mutant mice. Furthermore, microdialysis experiments revealed that methamphetamine-evoked dopamine release in the nucleus accumbens was reduced in Ptprz-KO mice and CS mutant mice. These results suggest that the extracellular region of PTPRZ, including the secretory isoform, is crucial for behavioral responses to novelty and the formation of aversive memories, whereas the PTPase activities of PTPRZ receptor isoforms are involved in regulating the dopaminergic system. [ABSTRACT FROM AUTHOR]

Visual cortex is organized into discrete sub-regions or areas that are arranged into a hierarchy and serves different functions in the processing of visual information. In retinotopic maps of mouse cortex, there appear to be substantial mouse-to-mouse differences in visual area location, size and shape. Here we quantify the biological variation in the size, shape and locations of 11 visual areas in the mouse, after separating biological variation and measurement noise. We find that there is biological variation in the locations and sizes of visual areas. [ABSTRACT FROM AUTHOR]

Sepsis is a life threatening condition which produces multi-organ dysfunction with profound circulatory and cellular derangements. Administration of E.Coli endotoxin (LPS) produces systemic inflammatory effects of sepsis including disruption of endothelial barrier, and if severe enough death. Whole body periodic acceleration (pGz) is the headward-footward motion of the body. pGz has been shown to induce pulsatile shear stress to the endothelium, thereby releasing vascular and cardio protective mediators. The purpose of this study was to determine whether or not pGz performed as a pre-treatment or post-treatment strategy improves survival in a lethal murine endotoxin model.This study was designed as a prospective randomized controlled study in mice. pGz was performed in mice as pre-treatment (pGz-LPS, 3 days prior to LPS), post-treatment (LPS- pGz, 30 min after LPS) strategies or Control (LPS-CONT), in a lethal murine model of endotoxemia. Endotoxemia was induced with intraperitoneal injection of E.Coli LPS (40mg/kg). In a separate group of mice, a nonspecific nitric oxide synthase inhibitor (L-NAME) was provided in their drinking water and pGz-LPS and LPS-pGz performed to determine the effect of nitric oxide (NO) inhibition on survival. In another subset of mice, micro vascular leakage was determined. Behavioral scoring around the clock was performed in all mice at 30 min intervals after LPS administration, until 48 hrs. survival or death. LPS induced 100% mortality in LPS-CONT animals by 30 hrs. In contrast, survival to 48 hrs. occurred in 60% of pGz-LPS and 80% of LPS-pGz. L-NAME abolished the survival effects of pGz. Microvascular leakage was markedly reduced in both pre and post pGz treated animals and was associated with increased tyrosine kinase endothelial-enriched tunica interna endothelial cell kinase 2 (TIE2) receptor and its phosphorylation (p-TIE2). In a murine model of lethal endotoxemia, pGz performed as a pre or post treatment strategy significantly improved survival, and markedly reduced microvascular leakage. The effect was modulated, in part, by NO since a non-selective inhibitor of NO abolished the pGz survival effect. [ABSTRACT FROM AUTHOR]

We show that in an animal model of anxiety the overall excitation, particularly in the infralimbic region of the medial prefrontal cortex (IL), is increased and that the activity ratio between excitatory pyramidal neurons and inhibitory interneurons (AR PN/IN) is shifted towards excitation. The same change in AR PN/IN is evident for wildtype mice, which have been exposed to an anxiety stimulus. We hypothesize, that an elevated activity and the imbalance of excitation (PN) and inhibition (IN) within the neuronal microcircuitry of the prefrontal cortex is responsible for anxiety behaviour and employed optogenetic methods in freely moving mice to verify our findings. Consistent with our hypothesis elevation of pyramidal neuron activity in the infralimbic region of the prefrontal cortex significantly enhanced anxiety levels in several behavioural tasks by shifting the AR PN/IN to excitation, without affecting motor behaviour, thus revealing a novel mechanism by which anxiety is facilitated. [ABSTRACT FROM AUTHOR]

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by impaired social interactions, difficulty with communication, and repetitive behavior patterns. In humans affected by ASD, there is a male pre-disposition towards the condition with a male to female ratio of 4:1. In part due to the complex etiology of ASD including genetic and environmental interplay, there are currently no available medical therapies to improve the social deficits of ASD. Studies in rodent models and humans have shown promising therapeutic effects of oxytocin in modulating social adaptation. One pharmacological approach to stimulating oxytocinergic activity is the melanocortin receptor 4 agonist Melanotan-II (MT-II). Notably the effects of oxytocin on environmental rodent autism models has not been investigated to date. We used a maternal immune activation (MIA) mouse model of autism to assess the therapeutic potential of MT-II on autism-like features in adult male mice. The male MIA mice exhibited autism-like features including impaired social behavioral metrics, diminished vocal communication, and increased repetitive behaviors. Continuous administration of MT-II to male MIA mice over a seven-day course resulted in rescue of social behavioral metrics. Normal background C57 male mice treated with MT-II showed no significant alteration in social behavioral metrics. Additionally, there was no change in anxiety-like or repetitive behaviors following MT-II treatment of normal C57 mice, though there was significant weight loss following subacute treatment. These data demonstrate MT-II as an effective agent for improving autism-like behavioral deficits in the adult male MIA mouse model of autism. [ABSTRACT FROM AUTHOR]

Tolerance to bitter foods and its potentiation by repetitive exposure are commonly experienced and potentially underlie the consumption of bitter foods, but it remains unknown whether permissive and adaptive responses are general phenomena for bitter-tasting substances or specific to certain substances, and they have not been rigorously studied in mice. Here, we investigated the effects of prolonged exposure to a bitter compound on both recognition and rejection behaviors to the same compound in mice. Paired measurements of rejection (RjT) and apparent recognition (aRcT) thresholds were conducted using brief-access two-bottle choice tests before and after taste aversion conditioning, respectively. First, RjT was much higher than aRcT for the bitter amino acids L-tryptophan and L-isoleucine, which mice taste daily in their food, indicating strong acceptance of those familiar stimuli within the concentration range between RjT and aRcT. Next, we tested five other structurally dissimilar bitter compounds, to which mice were naive at the beginning of experiments: denatonium benzoate, quinine-HCl, caffeine, salicin, and epigallocatechin gallate. RjT was moderately higher than aRcT for all the compounds tested, indicating the presence of innate acceptance to these various, unfamiliar bitter stimuli in mice. Lastly, a 3-week forced exposure increased RjT for all the bitter compounds except salicin, demonstrating that mice acquire tolerance to a broad array of bitter compounds after long-term exposure to them. Although the underlying mechanisms remain to be determined, our studies provide behavioral evidence of innate and acquired tolerance to various bitter stimuli in mice, suggesting its generality among bitterants. [ABSTRACT FROM AUTHOR]

CHIP (carboxyl terminus of heat shock 70-interacting protein) has long been recognized as an active member of the cellular protein quality control system given the ability of CHIP to function as both a co-chaperone and ubiquitin ligase. We discovered a genetic disease, now known as spinocerebellar autosomal recessive 16 (SCAR16), resulting from a coding mutation that caused a loss of CHIP ubiquitin ligase function. The initial mutation describing SCAR16 was a missense mutation in the ubiquitin ligase domain of CHIP (p.T246M). Using multiple biophysical and cellular approaches, we demonstrated that T246M mutation results in structural disorganization and misfolding of the CHIP U-box domain, promoting oligomerization, and increased proteasome-dependent turnover. CHIP-T246M has no ligase activity, but maintains interactions with chaperones and chaperone-related functions. To establish preclinical models of SCAR16, we engineered T246M at the endogenous locus in both mice and rats. Animals homozygous for T246M had both cognitive and motor cerebellar dysfunction distinct from those observed in the CHIP null animal model, as well as deficits in learning and memory, reflective of the cognitive deficits reported in SCAR16 patients. We conclude that the T246M mutation is not equivalent to the total loss of CHIP, supporting the concept that disease-causing CHIP mutations have different biophysical and functional repercussions on CHIP function that may directly correlate to the spectrum of clinical phenotypes observed in SCAR16 patients. Our findings both further expand our basic understanding of CHIP biology and provide meaningful mechanistic insight underlying the molecular drivers of SCAR16 disease pathology, which may be used to inform the development of novel therapeutics for this devastating disease. [ABSTRACT FROM AUTHOR]

In the European Union (EU) millions of laboratory mice are used and killed for experimental and other scientific purposes each year. Although controversially discussed, the use of carbon dioxide (CO2) is still permitted for killing rodents according to the Directive 2010/63/EU. Within the scope of refinement, our aim was to investigate if isoflurane and sevoflurane are an appropriate alternative killing method to CO2 in mice. Different concentrations of CO2 (filling rates of 20%, 60%, 100%; CO2 20, 60, 100), isoflurane (Iso 2%, 5%) and sevoflurane (Sevo 4.8%, 8%) were compared in two mouse strains (NMRI, C57Bl/6J) using a broad spectrum of behavioral parameters, including the approach-avoidance test, and analyzing blood for stress parameters (glucose, adrenaline, noradrenaline). We focused in our study on the period from the beginning of the gas inlet to loss of consciousness, as during this period animals are able to perceive pain and distress. Our results show that only higher concentrations of CO2 (CO2 60, 100) and isoflurane (5%) induced surgical tolerance within 300 s in both strains, with CO2 100 being the fastest acting inhalant anesthetic. The potency of halogenated ethers depended on the mouse strain, with C57Bl/6J being more susceptible than NMRI mice. Behavioral analysis revealed no specific signs of distress, e. g. stress-induced grooming, and pain, i. e. audible vocalizations, for all inhalant gases. However, adrenaline and noradrenaline plasma concentrations were increased, especially in NMRI mice exposed to CO2 in high concentrations, whereas we did not observe such increase in animals exposed to isoflurane or sevoflurane. Escape latencies in the approach-avoidance test using C57Bl/6J mice did not differ between the three inhalant gases, however, some animals became recumbent during isoflurane and sevoflurane but not during CO2 exposure. The rise in catecholamine concentrations suggests that CO2 exposure might be linked to a higher stress response compared to isoflurane and sevoflurane exposure, although we did not observe a behavioral correlate for that. Follow-up studies investigating other fast-acting stress hormones and central anxiety circuits are needed to confirm our findings. [ABSTRACT FROM AUTHOR]

Approaches to identify the perception of tinnitus in various animal models have been difficult to apply to mouse. As a result, mice have been underutilized to investigate the cellular, molecular, and genetic mechanisms underlying tinnitus. A recent study in guinea pigs identified a novel spontaneous behavior (unconditioned response), changes in movement during silent gaps, that identified a subgroup of animals presumably with tinnitus. Guinea pigs identified with tinnitus failed to “freeze” in response to silent gaps in sound. In the hope of developing a rapid and reliable assay for mice, we used a similar approach. C57BL/6J mice underwent three trials in which spontaneous movement was video recorded in the presence of white noise interrupted with six silent gaps. Movement metrics included velocity and body movement. Before the third trial, mice underwent either sham or noise exposure to induce hearing loss and tinnitus. Auditory brainstem responses before and after noise trauma confirmed normal hearing in sham-treated animals and hearing loss in the noise-exposed cohort. No differences in the various movement metrics were detected during the silent gaps either before or after sham/noise exposure. Variability in spontaneous movement both before and after sham/noise exposure was substantially greater in mice compared to guinea pigs. Thus, this assay is not sufficiently statistically powerful to identify changes in movement that might indicate tinnitus perception in mice. Previous observations also reported increased movement overall in guinea pigs identified as suffering tinnitus. In contrast, mice showed no statistically significant differences in movement between the three trials. Despite our results, other unconditioned (as well as conditioned) behaviors should be examined in mice to test their utility to detect changes that indicate the perception of tinnitus. Such assays are essential to accelerate the use of mouse models in tinnitus research. [ABSTRACT FROM AUTHOR]

We screened a library of botanical compounds purified from plants of Vietnam for modulators of the activity of a two-pore domain K+ channel, TREK-1, and we identified a hydroxycoumarin-related compound, ostruthin, as an activator of this channel. Ostruthin increased whole-cell TREK-1 channel currents in 293T cells at a low concentration (EC50 = 5.3 μM), and also activity of the TREK-2 channel (EC50 = 3.7 mM). In contrast, ostruthin inhibited other K+ channels, e.g. human ether-à-go-go-related gene (HERG1), inward-rectifier (Kir2.1), voltage-gated (Kv1.4), and two-pore domain (TASK-1) at higher concentrations, without affecting voltage-gated potassium channel (KCNQ1 and 3). We tested the effect of this compound on mouse anxiety- and depression-like behaviors and found anxiolytic activity in the open-field, elevated plus maze, and light/dark box tests. Of note, ostruthin also showed antidepressive effects in the forced swim and tail suspension tests, although previous studies reported that inhibition of TREK-1 channels resulted in an antidepressive effect. The anxiolytic and antidepressive effect was diminished by co-administration of a TREK-1 blocker, amlodipine, indicating the involvement of TREK-1 channels. Administration of ostruthin suppressed the stress-induced increase in anti-c-Fos immunoreactivity in the lateral septum, without affecting immunoreactivity in other mood disorder-related nuclei, e.g. the amygdala, paraventricular nuclei, and dorsal raphe nucleus. Ostruthin may exert its anxiolytic and antidepressive effects through a different mechanism from current drugs. [ABSTRACT FROM AUTHOR]

Recent investigations of Nogo-A, a well characterized protein inhibitor of neurite outgrowth in the brain, have revealed additional functions including a role in neuropsychiatric disorders such as schizophrenia. Here we examined Nogo-A functions in mouse CA3 hippocampal circuitry. Patch clamp recordings showed that the absence of Nogo-A results in a hyperactive network. In addition, mGlu3 metabotropic glutamate receptors, which exhibit mutations in certain forms of schizophrenia, were downregulated specifically in the CA3 area. Furthermore, Nogo-A-/- mice showed disordered theta oscillations with decreased incidence and frequency, similar to those observed in mGlu3-/- mice. As disruptions in theta rhythmicity are associated with impaired spatial navigation, we tested mice using modified Morris water maze tasks. Mice lacking Nogo-A exhibited altered search strategies, displaying greater dependence on global as opposed to local reference frames. This link between Nogo-A and mGlu3 receptors may provide new insights into mechanisms underlying schizophrenia. [ABSTRACT FROM AUTHOR]

Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders. Recently we have generated Cdkl5 KO mice by targeting exon 2 on the C57BL/6N background, and demonstrated postsynaptic overaccumulation of GluN2B-containing N-methyl-D-aspartate (NMDA) receptors in the hippocampus. In the current study, we subjected the Cdkl5 KO mice to a battery of comprehensive behavioral tests, aiming to reveal the effects of loss of CDKL5 in a whole perspective of motor, emotional, social, and cognition/memory functions, and to identify its undetermined roles. The neurological screen, rotarod, hot plate, prepulse inhibition, light/dark transition, open field, elevated plus maze, Porsolt forced swim, tail suspension, one-chamber and three-chamber social interaction, 24-h home cage monitoring, contextual and cued fear conditioning, Barnes maze, and T-maze tests were applied on adult Cdkl5 -/Y and +/Y mice. Cdkl5 -/Y mice showed a mild alteration in the gait. Analyses of emotional behaviors revealed significantly enhanced anxiety-like behaviors of Cdkl5 -/Y mice. Depressive-like behaviors and social interaction of Cdkl5 -/Y mice were uniquely altered. The contextual and cued fear conditioning of Cdkl5 -/Y mice were comparable to control mice; however, Cdkl5 -/Y mice showed a significantly increased freezing time and a significantly decreased distance traveled during the pretone period in the altered context. Both acquisition and long-term retention of spatial reference memory were significantly impaired. The morphometric analysis of hippocampal CA1 pyramidal neurons revealed impaired dendritic arborization and immature spine development in Cdkl5 -/Y mice. These results indicate that CDKL5 plays significant roles in regulating emotional behaviors especially on anxiety- and fear-related responses, and in both acquisition and long-term retention of spatial reference memory, which suggests that focus and special attention should be paid to the specific mechanisms of these deficits in the CDKL5 deficiency disorder. [ABSTRACT FROM AUTHOR]

Reduced expression of Sp4, the murine homolog of human SP4, a risk gene of multiple psychiatric disorders, led to N-methyl-D-aspartate (NMDA) hypofunction in mice, producing behavioral phenotypes reminiscent of schizophrenia, including hypersensitivity to ketamine. As accumulating evidence on molecular mechanisms and behavioral phenotypes established Sp4 hypomorphism as a promising animal model, systems-level neural circuit mechanisms of Sp4 hypomorphism, especially network dynamics underlying cognitive functions, remain poorly understood. We attempted to close this gap in knowledge in the present study by recording multi-channel epidural electroencephalogram (EEG) from awake behaving wildtype and Sp4 hypomorphic mice. We characterized cortical theta-band power and phase-coupling phenotypes, a known neural circuit substrate underlying cognitive functions, and further studied the effects of a subanesthetic dosage of ketamine on theta abnormalities unique to Sp4 hypomorphism. Sp4 hypomorphic mice had markedly elevated theta power localized frontally and parietally, a more pronounced theta phase progression along the neuraxis, and a stronger frontal-parietal theta coupling. Acute subanesthetic ketamine did not affect theta power in wildtype animals but significantly reduced it in Sp4 hypomorphic mice, nearly completely neutralizing their excessive frontal/parietal theta power. Ketamine did not significantly alter cortical theta phase progression in either wildtype or Sp4 hypomorphic animals, but significantly strengthened cortical theta phase-coupling in wildtype, but not in Sp4 hypomorphic animals. Our results suggested that the resting-state phenotypes of cortical theta oscillations unique to Sp4 hypomorphic mice closely mimicked a schizophrenic endophenotype. Further, ketamine independently modulated Sp4 hypomorphic anomalies in theta power and phase-coupling, suggesting separate underlying neural circuit mechanisms. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction plays a significant role in neurodegenerative disease including ataxias and other movement disorders, particularly those marked by progressive degeneration in the cerebellum. In this study, we investigate the role of mitochondrial oxidative phosphorylation (OXPHOS) deficits in cerebellar tissue of a Purkinje cell-driven spinocerebellar ataxia type 1 (SCA1) mouse. Using RNA sequencing transcriptomics, OXPHOS complex assembly analysis and oxygen consumption assays, we report that in the presence of mutant polyglutamine-expanded ataxin-1, SCA1 mice display deficits in cerebellar OXPHOS complex I (NADH-coenzyme Q oxidoreductase). Complex I genes are upregulated at the time of symptom onset and upregulation persists into late stage disease; yet, functional assembly of complex I macromolecules are diminished and oxygen respiration through complex I is reduced. Acute treatment of postsymptomatic SCA1 mice with succinic acid, a complex II (succinate dehydrogenase) electron donor to bypass complex I dysfunction, ameliorated cerebellar OXPHOS dysfunction, reduced cerebellar pathology and improved motor behavior. Thus, exploration of mitochondrial dysfunction and its role in neurodegenerative ataxias, and warrants further investigation. [ABSTRACT FROM AUTHOR]

In humans and rodents, stress promotes habit-based behaviors that can interfere with action—outcome decision-making. Further, developmental stressor exposure confers long-term habit biases across rodent—primate species. Despite these homologies, mechanisms remain unclear. We first report that exposure to the primary glucocorticoid corticosterone (CORT) in adolescent mice recapitulates multiple neurobehavioral consequences of stressor exposure, including long-lasting biases towards habit-based responding in a food-reinforced operant conditioning task. In both adolescents and adults, CORT also caused a shift in the balance between full-length tyrosine kinase receptor B (trkB) and a truncated form of this neurotrophin receptor, favoring the inactive form throughout multiple corticolimbic brain regions. In adolescents, phosphorylation of the trkB substrate extracellular signal-regulated kinase 42/44 (ERK42/44) in the ventral hippocampus was also diminished, a long-term effect that persisted for at least 12 wk. Administration of the trkB agonist 7,8-dihydroxyflavone (7,8-DHF) during adolescence at doses that stimulated ERK42/44 corrected long-lasting corticosterone-induced behavioral abnormalities. Meanwhile, viral-mediated overexpression of truncated trkB in the ventral hippocampus reduced local ERK42/44 phosphorylation and was sufficient to induce habit-based and depression-like behaviors. Together, our findings indicate that ventral hippocampal trkB is essential to goal-directed action selection, countering habit-based behavior otherwise facilitated by developmental stress hormone exposure. They also reveal an early-life sensitive period during which trkB—ERK42/44 tone determines long-term behavioral outcomes. [ABSTRACT FROM AUTHOR]

Alterations in the social and cognitive domain are considered important indicators for increased disability in many stress-related disorders. Similar impairments have been observed in rodents chronically exposed to stress, mimicking potential endophenotypes of stress-related psychopathologies such as major depression disorder (MDD), anxiety, conduct disorder, and posttraumatic stress disorder (PTSD). Data from numerous studies suggest that deficient plasticity mechanisms in hippocampus (HC) and prefrontal cortex (PFC) might underlie these social and cognitive deficits. Specifically, stress-induced deficiencies in neural plasticity have been associated with a hypodopaminergic state and reduced neural plasticity persistence. Here we assessed the effects of unpredictable chronic mild stress (UCMS) on exploratory, social and cognitive behavior of females of two inbred mouse strains (C57BL/6J and DBA/2J) that differ in their dopaminergic profile. Exposure to chronic stress resulted in impaired circadian rhythmicity, sociability and social cognition in both inbred strains, but differentially affected activity patterns and contextual discrimination performance. These stress-induced behavioral impairments were accompanied by reduced expression levels of brain derived neurotrophic factor (BDNF) in the prefrontal cortex. The strain-specific cognitive impairment was coexistent with enhanced plasma corticosterone levels and reduced expression of genes related to dopamine signaling in hippocampus. These results underline the importance of assessing different strains with multiple test batteries to elucidate the neural and genetic basis of social and cognitive impairments related to chronic stress. [ABSTRACT FROM AUTHOR]

The application of complex network modeling to analyze large co-expression data sets has gained traction during the last decade. In particular, the use of the weighted gene co-expression network analysis framework has allowed an unbiased and systems-level investigation of genotype-phenotype relationships in a wide range of systems. Since mouse is an important model organism for biomedical research on human disease, it is of great interest to identify similarities and differences in the functional roles of human and mouse orthologous genes. Here, we develop a novel network comparison approach which we demonstrate by comparing two gene-expression data sets from a large number of human and mouse tissues. The method uses weighted topological overlap alongside the recently developed network-decomposition method of s-core analysis, which is suitable for making gene-centrality rankings for weighted networks. The aim is to identify globally central genes separately in the human and mouse networks. By comparing the ranked gene lists, we identify genes that display conserved or diverged centrality-characteristics across the networks. This framework only assumes a single threshold value that is chosen from a statistical analysis, and it may be applied to arbitrary network structures and edge-weight distributions, also outside the context of biology. When conducting the comparative network analysis, both within and across the two species, we find a clear pattern of enrichment of transcription factors, for the homeobox domain in particular, among the globally central genes. We also perform gene-ontology term enrichment analysis and look at disease-related genes for the separate networks as well as the network comparisons. We find that gene ontology terms related to regulation and development are generally enriched across the networks. In particular, the genes FOXE3, RHO, RUNX2, ALX3 and RARA, which are disease genes in either human or mouse, are on the top-10 list of globally central genes in the human and mouse networks. [ABSTRACT FROM AUTHOR]

Eye movements provide insights into what people pay attention to, and therefore are commonly included in a variety of human-computer interaction studies. Eye movement recording devices (eye trackers) produce gaze trajectories, that is, sequences of gaze location on the screen. Despite recent technological developments that enabled more affordable hardware, gaze data are still costly and time consuming to collect, therefore some propose using mouse movements instead. These are easy to collect automatically and on a large scale. If and how these two movement types are linked, however, is less clear and highly debated. We address this problem in two ways. First, we introduce a new movement analytics methodology to quantify the level of dynamic interaction between the gaze and the mouse pointer on the screen. Our method uses volumetric representation of movement, the space-time densities, which allows us to calculate interaction levels between two physically different types of movement. We describe the method and compare the results with existing dynamic interaction methods from movement ecology. The sensitivity to method parameters is evaluated on simulated trajectories where we can control interaction levels. Second, we perform an experiment with eye and mouse tracking to generate real data with real levels of interaction, to apply and test our new methodology on a real case. Further, as our experiment tasks mimics route-tracing when using a map, it is more than a data collection exercise and it simultaneously allows us to investigate the actual connection between the eye and the mouse. We find that there seem to be natural coupling when eyes are not under conscious control, but that this coupling breaks down when instructed to move them intentionally. Based on these observations, we tentatively suggest that for natural tracing tasks, mouse tracking could potentially provide similar information as eye-tracking and therefore be used as a proxy for attention. However, more research is needed to confirm this. [ABSTRACT FROM AUTHOR]

Koolen-de Vries syndrome (KdVS) is a multi-system disorder characterized by intellectual disability, friendly behavior, and congenital malformations. The syndrome is caused either by microdeletions in the 17q21.31 chromosomal region or by variants in the KANSL1 gene. The reciprocal 17q21.31 microduplication syndrome is associated with psychomotor delay, and reduced social interaction. To investigate the pathophysiology of 17q21.31 microdeletion and microduplication syndromes, we generated three mouse models: 1) the deletion (Del/+); or 2) the reciprocal duplication (Dup/+) of the 17q21.31 syntenic region; and 3) a heterozygous Kansl1 (Kans1+/-) model. We found altered weight, general activity, social behaviors, object recognition, and fear conditioning memory associated with craniofacial and brain structural changes observed in both Del/+ and Dup/+ animals. By investigating hippocampus function, we showed synaptic transmission defects in Del/+ and Dup/+ mice. Mutant mice with a heterozygous loss-of-function mutation in Kansl1 displayed similar behavioral and anatomical phenotypes compared to Del/+ mice with the exception of sociability phenotypes. Genes controlling chromatin organization, synaptic transmission and neurogenesis were upregulated in the hippocampus of Del/+ and Kansl1+/- animals. Our results demonstrate the implication of KANSL1 in the manifestation of KdVS phenotypes and extend substantially our knowledge about biological processes affected by these mutations. Clear differences in social behavior and gene expression profiles between Del/+ and Kansl1+/- mice suggested potential roles of other genes affected by the 17q21.31 deletion. Together, these novel mouse models provide new genetic tools valuable for the development of therapeutic approaches. [ABSTRACT FROM AUTHOR]

The Barnes maze is one of the main behavioral tasks used to study spatial learning and memory. The Barnes maze is a task conducted on “dry land” in which animals try to escape from a brightly lit exposed circular open arena to a small dark escape box located under one of several holes at the periphery of the arena. In comparison with another classical spatial learning and memory task, the Morris water maze, the negative reinforcements that motivate animals in the Barnes maze are less severe and less stressful. Furthermore, the Barnes maze is more compatible with recently developed cutting-edge techniques in neural circuit research, such as the miniature brain endoscope or optogenetics. For this study, we developed a lift-type task start system and equipped the Barnes maze with it. The subject mouse is raised up by the lift and released into the maze automatically so that it can start navigating the maze smoothly from exactly the same start position across repeated trials. We believe that a Barnes maze test with a lift-type task start system may be useful for behavioral experiments when combined with head-mounted or wire-connected devices for online imaging and intervention in neural circuits. Furthermore, we introduced a network analysis method for the analysis of the Barnes maze data. Each animal’s exploratory behavior in the maze was visualized as a network of nodes and their links, and spatial learning in the maze is described by systematic changes in network structures of search behavior. Network analysis was capable of visualizing and quantitatively analyzing subtle but significant differences in an animal’s exploratory behavior in the maze. [ABSTRACT FROM AUTHOR]

Purpose: Total salvianolic acid (TSA) is extracted from salvia miltiorrhiza; however, to date, there has been limited characterization of its effects on metabolites in Alzheimer’s disease model-APPswe/PS1dE9 mice. The main objective of this study was to investigate the metabolic changes in 7-month-old APPswe/PS1dE9 mice treated with TSA, which protects against learning and memory impairment. Methods: APPswe/PS1dE9 mice were treated with TSA (30 mg/kg·d and 60 mg/kg·d, i.p.) and saline (i.p.) daily from 3.5 months old for 14 weeks; saline-treated (i.p.) WT mice were included as the controls. The effects of TSA on learning and memory were assessed by a series of behavioral tests, including the NOR, MWM and step-through tasks. The FBG and plasma lipid levels were subsequently assessed using the GOPOD and enzymatic color methods, respectively. Finally, the concentrations of Aβ42, Aβ40 and metabolites in the hippocampus of the mice were detected via ELISA and GC-TOF-MS, respectively. Results: At 7 months of age, the APPswe/PS1dE9 mice treated with TSA exhibited an improvement in the preference index (PI) one hour after the acquisition phase in the NOR and the preservation of spatial learning and memory in the MWM. Treatment with TSA substantially decreased the LDL-C level, and 60 mg/kg TSA decreased the CHOL level compared with the plasma level of the APPswe/PS1dE9 group. The Aβ42 and Aβ40 levels in the hippocampus were decreased in the TSA-treated group compared with the saline-treated APPswe/PS1dE9 group. The regulation of metabolic pathways relevant to TSA predominantly included carbohydrate metabolism, such as sorbitol, glucose-6-phosphate, sucrose-6-phosphate and galactose, vitamin metabolism involved in cholecalciferol and ascorbate in the hippocampus. Conclusions: TSA induced a remarkable amelioration of learning and memory impairments in APPswe/PS1dE9 mice through the regulation of Aβ42, Aβ40, carbohydrate and vitamin metabolites in the hippocampus and LDL-C and CHOL in the plasma. [ABSTRACT FROM AUTHOR]

Tetraspanins (Tspan) are transmembrane proteins with important scaffold and signalling functions. Deletions of Tetraspanin 6 (Tspan6) gene, a member of the tetraspanin family, have been reported in patients with Epilepsy Female-restricted with Mental Retardation (EFMR). Interestingly, mutations in Tspan7, highly homologous to Tspan6, are associated with X-linked intellectual disability, suggesting that these two proteins are important for cognition. Considering recent evidences showing that Tspan7 plays a key role in synapse development and AMPAR trafficking, we initiated the study of Tspan6 in synaptic function using a Tspan6 knock out mouse model. Here we report that hippocampal field recordings from Tspan6 knock out mice show an enhanced basal synaptic transmission and impaired long term potentiation (LTP). A normal paired-pulse facilitation response suggests that Tspan6 affects the properties of the postsynaptic rather than the presynaptic terminal. However, no changes in spine morphology or postsynaptic markers could be detected in Tspan6 KO mice compared with wild types. In addition, Tspan6 KO mice show normal locomotor behaviour and no defects in hippocampus-dependent memory tests. [ABSTRACT FROM AUTHOR]

Fingolimod, the first oral, disease-modifying therapy for MS, has been recently proposed to modulate glutamate transmission in the central nervous system (CNS) of mice suffering from Experimental Autoimmune Encephalomyelitis (EAE) and in MS patients. Our study aims at investigating whether oral fingolimod recovers presynaptic defects that occur at different stages of disease in the CNS of EAE mice. In vivo prophylactic (0.3 mg/kg for 14 days, from the 7th day post immunization, d.p.i, the drug dissolved in the drinking water) fingolimod significantly reduced the clinical symptoms and the anxiety-related behaviour in EAE mice. Spinal cord inflammation, demyelination and glial cell activation are markers of EAE progression. These signs were ameliorated following oral fingolimod administration. Glutamate exocytosis was shown to be impaired in cortical and spinal cord terminals isolated from EAE mice at 21 ± 1 d.p.i., while GABA alteration emerged only at the spinal cord level. Prophylactic fingolimod recovered these presynaptic defects, restoring altered glutamate and GABA release efficiency. The beneficial effect occurred in a dose-dependent, region-specific manner, since lower (0.1–0.03 mg/kg) doses restored, although to a different extent, synaptic defects in cortical but not spinal cord terminals. A delayed reduction of glutamate, but not of GABA, exocytosis was observed in hippocampal terminals of EAE mice at 35 d.p.i. Therapeutic (0.3 mg/kg, from 21 d.p.i. for 14 days) fingolimod restored glutamate exocytosis in the cortex and in the hippocampus of EAE mice at 35 ± 1 d.p.i. but not in the spinal cord, where also GABAergic defects remained unmodified. These results improve our knowledge of the molecular events accounting for the beneficial effects elicited by fingolimod in demyelinating disorders. [ABSTRACT FROM AUTHOR]

Terminal Schwann cells (TSCs) are specialized cells that envelop the motor nerve terminal, and play a role in the maintenance and regeneration of neuromuscular junctions (NMJs). The chemorepulsive protein semaphorin 3A (SEMA3A) is selectively up-regulated in TSCs on fast-fatigable muscle fibers following experimental denervation of the muscle (BotoxA-induced paralysis or crush injury to the sciatic nerve) or in the motor neuron disease amyotrophic lateral sclerosis (ALS). Re-expression of SEMA3A in this subset of TSCs is thought to play a role in the selective plasticity of nerve terminals as observed in ALS and following BotoxA-induced paralysis. Using a mouse model expressing a mutant SEMA3A with diminished signaling capacity, we studied the influence of SEMA3A signaling at the NMJ with two denervation paradigms; a motor neuron disease model (the G93A-hSOD1 ALS mouse line) and an injury model (BotoxA-induced paralysis). ALS mice that either expressed 1 or 2 mutant SEMA3A alleles demonstrated no difference in ALS-induced decline in motor behavior. We also investigated the effects of BotoxA-induced paralysis on the sprouting capacity of NMJs in the K108N-SEMA3A mutant mouse, and observed no change in the differential neuronal plasticity found at NMJs on fast-fatigable or slow muscle fibers due to the presence of the SEMA3A mutant protein. Our data may be explained by the residual repulsive activity of the mutant SEMA3A, or it may imply that SEMA3A alone is not a key component of the molecular signature affecting NMJ plasticity in ALS or BotoxA-induced paralysis. Interestingly, we did observe a sex difference in motor neuron sprouting behavior after BotoxA-induced paralysis in WT mice which we speculate may be an important factor in the sex dimorphic differences seen in ALS. [ABSTRACT FROM AUTHOR]

Mitral cells (MCs) of the mammalian olfactory bulb have a single primary dendrite extending into a single glomerulus, where they receive odor information from olfactory sensory neurons (OSNs). Molecular mechanisms for controlling dendritic arbors of MCs, which dynamically change during development, are largely unknown. Here we found that MCs displayed more complex dendritic morphologies in mouse mutants of Maml1, a crucial gene in Notch signaling. Similar phenotypes were observed by conditionally misexpressing a dominant negative form of MAML1 (dnMAML1) in MCs after their migration. Conversely, conditional misexpression of a constitutively active form of Notch reduced their dendritic complexity. Furthermore, the intracellular domain of Notch1 (NICD1) was localized to nuclei of MCs. These findings suggest that Notch signaling at embryonic stages is involved in the dendritic complexity of MCs. After the embryonic misexpression of dnMAML1, many MCs aberrantly extended dendrites to more than one glomerulus at postnatal stages, suggesting that Notch signaling is essential for proper formation of olfactory circuits. Moreover, dendrites in cultured MCs were shortened by Jag1-expressing cells. Finally, blocking the activity of Notch ligands in OSNs led to an increase in dendritic complexity as well as a decrease in NICD1 signals in MCs. These results demonstrate that the dendritic complexity of MCs is controlled by their presynaptic partners, OSNs. [ABSTRACT FROM AUTHOR]

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease caused by loss of motor neurons. ALS patients experience rapid deterioration in muscle function with an average lifespan of 3–5 years after diagnosis. Currently, the most effective therapeutic only extends lifespan by a few months, thus highlighting the need for new and improved therapies. Neurotrophic factors (NTFs) are important for neuronal development, maintenance, and survival. NTF treatment has previously shown efficacy in pre-clinical ALS models. However, clinical trials using NTFs produced no major improvements in ALS patients, due in part to the limited blood brain barrier (BBB) penetration. In this study we assessed the potential neuroprotective effects of a novel class of compounds known as MicroNeurotrophins (MNTs). MNTs are derivatives of Dehydroepiandrosterone (DHEA), an endogenous neurosteroid that can cross the BBB and bind to tyrosine kinase receptors mimicking the pro-survival effects of NTFs. Here we sought to determine whether MNTs were neuroprotective in two different models of ALS. Our results demonstrate that BNN27 (10 μM) attenuated loss of motor neurons co-cultured with astrocytes derived from human ALS patients with SOD1 mutations via the reduction of oxidative stress. Additionally, in the G93A SOD1 mouse, BNN27 (10 mg/kg) treatment attenuated motor behavioral impairment in the paw grip endurance and rotarod tasks at postnatal day 95 in female but not male mice. In contrast, BNN27 (10 mg/kg and 50 mg/kg) treatment did not alter any other behavioral outcome or neuropathological marker in male or female mice. Lastly, BNN27 was not detected in post-mortem brain or spinal cord tissue of treated mice due to the rapid metabolism of BNN27 by mouse hepatocytes relative to human hepatocytes. Together, these findings demonstrate that BNN27 treatment failed to yield significant neuroprotective effects in the G93A SOD1 model likely due to its rapid rate of metabolism in mice. [ABSTRACT FROM AUTHOR]

Mounting evidence suggests the interaction between stress and genetics contribute to the development of depressive symptoms. Currently, the molecular mechanisms mediating this process are poorly understood, hindering the development of new clinical interventions. Here, we investigate the interaction between neuropsin, a serine protease, and chronic stress on the development of depressive-like behaviours in mice. We found no difference in baseline behaviour between neuropsin knockout and wild-type mice. However, our results show that neuropsin knockout mice are protected against the development of depressive-like behaviours and memory impairment following chronic stress. We hypothesised that this difference in behaviour may be due to an interaction between neuropsin and elevated plasma corticosterone. To test this, we subjected mice to chronic corticosterone injections. These injections resulted in changes to hippocampal structure similar to that observed following chronic stress. We found that inactivation of neuropsin limits the extent of these anatomical changes in both the chronic stress and the corticosterone injection exposed cohorts. We next used viral vectors to knockdown or overexpress neuropsin in the hippocampus to confirm the results of the KO study. Additionally, we found that inactivation of neuropsin limited glutamate dysregulation, associated with increased generation of reactive oxygen species, resulting from prolonged elevated plasma corticosterone. In this study, we demonstrate that neuropsin inactivation protects against the impairment of hippocampal functions and the depressive-like behaviour induced by chronic stress or high levels of corticosterone. Consequently, we suggest neuropsin is a potential target for clinical interventions for the management of stress disorders. [ABSTRACT FROM AUTHOR]

Phospholipase D2 (PLD2) is an enzyme that produces phosphatidic acid (PA), a lipid messenger molecule involved in a number of cellular events including, through its membrane curvature properties, endocytosis. The PLD2 knock out (PLD2KO) mouse has been previously reported to be protected from insult in a model of Alzheimer's disease. We have further analysed a PLD2KO mouse using mass spectrophotometry of its lipids and found significant differences in PA species throughout its brain. We have examined the expression pattern of PLD2 which allowed us to define which region of the brain to analyse for defect, notably PLD2 was not detected in glial-rich regions. The expression pattern lead us to specifically examine the mitral cells of olfactory bulbs, the Cornus Amonis (CA) regions of the hippocampus and the Purkinje cells of the cerebellum. We find that the change to longer PA species correlates with subtle architectural defect in the cerebellum, exemplified by ectopic Purkinje cells and an adult-onset deficit of olfaction. These observations draw parallels to defects in the reelin heterozygote as well as the effect of high fat diet on olfaction. [ABSTRACT FROM AUTHOR]

Blunt impact produces a heterogeneous brain injury in people and in animal models of traumatic brain injury. We report that a single closed head impact to adult C57/BL6 mice produced two injury syndromes (CHI-1 and CHI-2). CHI-1 mice spontaneously reinitiated breathing after injury while CHI-2 mice had prolonged apnea and regained breathing only after cardiopulmonary resuscitation and supplementation of 100% O2. The CHI-1 group significantly regained righting reflex more rapidly than the CHI-2 group. At 7 days post-injury, CHI-1, but not CHI-2 mice, acquired but had no long-term retention of an active place avoidance task. The behavioral deficits of CHI-1 and CHI-2 mice were retained one-month after the injury. CHI-1 mice had loss of hippocampal neurons and localized white matter injury at one month after injury. CHI-2 had a larger loss of hippocampal neurons and more widespread loss of myelin and axons. High-speed videos made during the injury were followed by assessment of breathing and righting reflex. These videos show that CHI-2 mice experienced a larger vertical g-force than CHI-1 mice. Time to regain righting reflex in CHI-2 mice significantly correlated with vertical g-force. Thus, physiological responses occurring immediately after injury can be valuable surrogate markers of subsequent behavioral and histological deficits. [ABSTRACT FROM AUTHOR]

Grooming is a complex and robust innate behavior, commonly performed by most vertebrate species. In mice, grooming consists of a series of stereotyped patterned strokes, performed along the rostro-caudal axis of the body. The frequency and duration of each grooming episode is sensitive to changes in stress levels, social interactions and pharmacological manipulations, and is therefore used in behavioral studies to gain insights into the function of brain regions that control movement execution and anxiety. Traditional approaches to analyze grooming rely on manually scoring the time of onset and duration of each grooming episode, and are often performed on grooming episodes triggered by stress exposure, which may not be entirely representative of spontaneous grooming in freely-behaving mice. This type of analysis is time-consuming and provides limited information about finer aspects of grooming behaviors, which are important to understand movement stereotypy and bilateral coordination in mice. Currently available commercial and freeware video-tracking software allow automated tracking of the whole body of a mouse or of its head and tail, not of individual forepaws. Here we describe a simple experimental set-up and a novel open-source code, named M-Track, for simultaneously tracking the movement of individual forepaws during spontaneous grooming in multiple freely-behaving mice. This toolbox provides a simple platform to perform trajectory analysis of forepaw movement during distinct grooming episodes. By using M-track we show that, in C57BL/6 wild type mice, the speed and bilateral coordination of the left and right forepaws remain unaltered during the execution of distinct grooming episodes. Stress exposure induces a profound increase in the length of the forepaw grooming trajectories. M-Track provides a valuable and user-friendly interface to streamline the analysis of spontaneous grooming in biomedical research studies. [ABSTRACT FROM AUTHOR]

Sevoflurane exposure impairs the long-term memory in neonates. Whether the exposure to animals in adolescence affects the memory, however, has been unclear. A small hydrolase enzyme of guanosine triphosphate (GTPase) rac1 plays a role in the F-actin dynamics related to the synaptic plasticity, as well as superoxide production via reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation. The current study was designed to examine whether sevoflurane exposure to mice in early adolescence modifies the long-term learning ability concomitantly with the changes in F-actin constitution as well as superoxide production in the hippocampus according to the levels of rac1 protein expression. Four-week-old mice were subjected to the evaluation of long-term learning ability for three days. On day one, each mouse was allowed to enter a dark chamber for five min to acclimatization. On day two, the procedure was repeated with the addition of an electric shock as soon as a mouse entered the dark chamber. All mice subsequently inhaled 2 L/min air with (Sevoflurane group) and without (Control group) 2.5% sevoflurane for three hours. On day three, each mouse was placed on the platform and retention time, which is the latency to enter the dark chamber, was examined. The brain removed after the behavior test, was used for analyses of immunofluorescence, Western immunoblotting and intracellular levels of superoxide. Sevoflurane exposure significantly prolonged retention time, indicating the enhanced long-term memory. Sevoflurane inhalation augmented F-actin constitution coexisting with the rac1 protein overexpression in the hippocampus whereas it did not alter the levels of superoxide. Sevoflurane exposure to 4-week-old mice accelerates the long-term memory concomitantly with the enhanced F-actin constitution coexisting with the small GTPase rac1 overexpression in the hippocampus. These results suggest that sevoflurane inhalation may amplify long-term memory consolidation via the increased cytoskeleton constitution in the hippocampus of animals in early adolescence. [ABSTRACT FROM AUTHOR]

To study the neuronal deficits in neuronopathic Gaucher Disease (nGD), the chronological behavioral profiles and the age of onset of brain abnormalities were characterized in a chronic nGD mouse model (9V/null). Progressive accumulation of glucosylceramide (GC) and glucosylsphingosine (GS) in the brain of 9V/null mice were observed at as early as 6 and 3 months of age for GC and GS, respectively. Abnormal accumulation of α-synuclein was present in the 9V/null brain as detected by immunofluorescence and Western blot analysis. In a repeated open-field test, the 9V/null mice (9 months and older) displayed significantly less environmental habituation and spent more time exploring the open-field than age-matched WT group, indicating the onset of short-term spatial memory deficits. In the marble burying test, the 9V/null group had a shorter latency to initiate burying activity at 3 months of age, whereas the latency increased significantly at ≥12 months of age; 9V/null females buried significantly more marbles to completion than the WT group, suggesting an abnormal response to the instinctive behavior and an abnormal activity in non-associative anxiety-like behavior. In the conditional fear test, only the 9V/null males exhibited a significant decrease in response to contextual fear, but both genders showed less response to auditory-cued fear compared to age- and gender-matched WT at 12 months of age. These results indicate hippocampus-related emotional memory defects. Abnormal gait emerged in 9V/null mice with wider front-paw and hind-paw widths, as well as longer stride in a gender-dependent manner with different ages of onset. Significantly higher liver- and spleen-to-body weight ratios were detected in 9V/null mice with different ages of onsets. These data provide temporal evaluation of neurobehavioral dysfunctions and brain pathology in 9V/null mice that can be used for experimental designs to evaluate novel therapies for nGD. [ABSTRACT FROM AUTHOR]

Recent findings suggest that memory allocation to specific neurons (i.e., neuronal allocation) in the amygdala is not random, but rather the transcription factor cAMP-response element binding protein (CREB) modulates this process, perhaps by regulating the transcription of channels that control neuronal excitability. Here, optogenetic studies in the mouse lateral amygdala (LA) were used to demonstrate that CREB and neuronal excitability regulate which neurons encode an emotional memory. To test the role of CREB in memory allocation, we overexpressed CREB in the lateral amygdala to recruit the encoding of an auditory-fear conditioning (AFC) memory to a subset of neurons. Then, post-training activation of these neurons with Channelrhodopsin-2 was sufficient to trigger recall of the memory for AFC, suggesting that CREB regulates memory allocation. To test the role of neuronal excitability in memory allocation, we used a step function opsin (SFO) to transiently increase neuronal excitability in a subset of LA neurons during AFC. Post-training activation of these neurons with Volvox Channelrhodopsin-1 was able to trigger recall of that memory. Importantly, our studies show that activation of the SFO did not affect AFC by either increasing anxiety or by strengthening the unconditioned stimulus. Our findings strongly support the hypothesis that CREB regulates memory allocation by modulating neuronal excitability. [ABSTRACT FROM AUTHOR]

γ-crystallins are major components of the vertebrate lens but show expression in other tissues as well. Their extralenticular functions remain so far unclear. Here, we explored such roles in the rodent superior olivary complex in which previous analysis demonstrated developmentally regulated expression of Crygd, Cryge and Crygn. Immunohistochemistry with novel antibodies against Crygd/e and Crygn indicate that expression of Crygd/e was moderate and varied between the perinatal superior olivary complex of mice, rats, and gerbils. Crygn-immunoreactivity was more robust and consistently highest in the medial nucleus of the trapezoid body, but also present in other nuclei of the superior olivary complex. To analyze the function of Crygn in the auditory hindbrain, we used a Crygn allele with a floxed exon 2. Upon pairing with Egr2::Cre mice, exon 2, encoding the first two greek key motifs of Crygn, was deleted in the developing auditory hindbrain. Anatomical analysis of these mice revealed a 20% volume reduction in the medial nucleus of the trapezoid body and a 7% reduction in the lateral superior olive at postnatal day 25. This was due to cell loss between postnatal days 4 and 25, whereas cell size was unaffected. Auditory brainstem responses showed normal threshold but a significant increase in the amplitude of wave IV. Crygn is hence required for postmigratory survival and proper function of auditory hindbrain neurons. These results ascertain for the first time an essential extralenticular role for γ-crystallins in vivo. [ABSTRACT FROM AUTHOR]

Mutations in CCM1 (aka KRIT1), CCM2, or CCM3 (aka PDCD10) gene cause cerebral cavernous malformation in humans. Mouse models of CCM disease have been established by deleting Ccm genes in postnatal animals. These mouse models provide invaluable tools to investigate molecular mechanism and therapeutic approaches for CCM disease. However, the full value of these animal models is limited by the lack of an accurate and quantitative method to assess lesion burden and progression. In the present study we have established a refined and detailed contrast enhanced X-ray micro-CT method to measure CCM lesion burden in mouse brains. As this study utilized a voxel dimension of 9.5μm (leading to a minimum feature size of approximately 25μm), it is therefore sufficient to measure CCM lesion volume and number globally and accurately, and provide high-resolution 3-D mapping of CCM lesions in mouse brains. Using this method, we found loss of Ccm1 or Ccm2 in neonatal endothelium confers CCM lesions in the mouse hindbrain with similar total volume and number. This quantitative approach also demonstrated a rescue of CCM lesions with simultaneous deletion of one allele of Mekk3. This method would enhance the value of the established mouse models to study the molecular basis and potential therapies for CCM and other cerebrovascular diseases. [ABSTRACT FROM AUTHOR]

3D volume imaging using iDISCO+ was applied to observe the spatial and temporal progression of tau pathology in deep structures of the brain of a mouse model that recapitulates the earliest stages of Alzheimer’s disease (AD). Tau pathology was compared at four timepoints, up to 34 months as it spread through the hippocampal formation and out into the neocortex along an anatomically connected route. Tau pathology was associated with significant gliosis. No evidence for uptake and accumulation of tau by glia was observed. Neuronal cells did appear to have internalized tau, including in extrahippocampal areas as a small proportion of cells that had accumulated human tau protein did not express detectible levels of human tau mRNA. At the oldest timepoint, mature tau pathology in the entorhinal cortex (EC) was associated with significant cell loss. As in human AD, mature tau pathology in the EC and the presence of tau pathology in the neocortex correlated with cognitive impairment. 3D volume imaging is an ideal technique to easily monitor the spread of pathology over time in models of disease progression. [ABSTRACT FROM AUTHOR]

Mammals show a wide range of brain sizes, reflecting adaptation to diverse habitats. Comparing interareal cortical networks across brains of different sizes and mammalian orders provides robust information on evolutionarily preserved features and species-specific processing modalities. However, these networks are spatially embedded, directed, and weighted, making comparisons challenging. Using tract tracing data from macaque and mouse, we show the existence of a general organizational principle based on an exponential distance rule (EDR) and cortical geometry, enabling network comparisons within the same model framework. These comparisons reveal the existence of network invariants between mouse and macaque, exemplified in graph motif profiles and connection similarity indices, but also significant differences, such as fractionally smaller and much weaker long-distance connections in the macaque than in mouse. The latter lends credence to the prediction that long-distance cortico-cortical connections could be very weak in the much-expanded human cortex, implying an increased susceptibility to disconnection syndromes such as Alzheimer disease and schizophrenia. Finally, our data from tracer experiments involving only gray matter connections in the primary visual areas of both species show that an EDR holds at local scales as well (within 1.5 mm), supporting the hypothesis that it is a universally valid property across all scales and, possibly, across the mammalian class. [ABSTRACT FROM AUTHOR]

Background: Major depression is a prevalent mood disorder. Chronic stress is presumably main etiology that leads to the neuron and synapse atrophies in the limbic system. However, the intermediate molecules from stresses to neuronal atrophy remain elusive, which we have studied in the medial prefrontal cortices from depression mice. Methods and Results: The mice were treated by the chronic unpredictable mild stress (CUMS) until they expressed depression-like behaviors confirmed by the tests of sucrose preference, forced swimming and Y-maze. High-throughput sequencings of microRNA and mRNA in the medial prefrontal cortices were performed in CUMS-induced depression mice versus control mice to demonstrate the molecular profiles of major depression. In the medial prefrontal cortices of depression-like mice, the levels of mRNAs that translated the proteins for the GABAergic synapses, dopaminergic synapses, myelination, synaptic vesicle cycle and neuronal growth were downregulated. miRNAs of regulating these mRNAs are upregulated. Conclusion: The deteriorations of GABAergic and dopaminergic synapses as well as axonal growth are associated with CUMS-induced depression. [ABSTRACT FROM AUTHOR]

One of the major histopathological hallmarks of Alzheimer’s disease (AD) is cerebral deposits of extracellular β-amyloid peptides. Preclinical studies have pointed to glucagon-like peptide 1 (GLP-1) receptors as a potential novel target in the treatment of AD. GLP-1 receptor agonists, including exendin-4 and liraglutide, have been shown to promote plaque-lowering and mnemonic effects of in a number of experimental models of AD. Transgenic mouse models carrying genetic mutations of amyloid protein precursor (APP) and presenilin-1 (PS1) are commonly used to assess the pharmacodynamics of potential amyloidosis-lowering and pro-cognitive compounds. In this study, effects of long-term liraglutide treatment were therefore determined in two double APP/PS1 transgenic mouse models of Alzheimer’s disease carrying different clinical APP/PS1 mutations, i.e. the ‘London’ (hAPPLon/PS1A246E) and ‘Swedish’ mutation variant (hAPPSwe/PS1ΔE9) of APP, with co-expression of distinct PS1 variants. Liraglutide was administered in 5 month-old hAPPLon/PS1A246E mice for 3 months (100 or 500 ng/kg/day, s.c.), or 7 month-old hAPPSwe/PS1ΔE9 mice for 5 months (500 ng/kg/day, s.c.). In both models, regional plaque load was quantified throughout the brain using stereological methods. Vehicle-dosed hAPPSwe/PS1ΔE9 mice exhibited considerably higher cerebral plaque load than hAPPLon/PS1A246E control mice. Compared to vehicle-dosed transgenic controls, liraglutide treatment had no effect on the plaque levels in hAPPLon/PS1A246E and hAPPSwe/PS1ΔE9 mice. In conclusion, long-term liraglutide treatment exhibited no effect on cerebral plaque load in two transgenic mouse models of low- and high-grade amyloidosis, which suggests differential sensitivity to long-term liraglutide treatment in various transgenic mouse models mimicking distinct pathological hallmarks of AD. [ABSTRACT FROM AUTHOR]

Abnormalities in tactile perception, such as sensory defensiveness, are common features in autism spectrum disorder (ASD). While not a diagnostic criterion for ASD, deficits in tactile perception contribute to the observed lack of social communication skills. However, the influence of tactile perception deficits on the development of social behaviors remains uncertain, as do the effects on neuronal circuits related to the emotional regulation of social interactions. In neonatal rodents, whiskers are the most important tactile apparatus, so bilateral whisker trimming is used as a model of early tactile deprivation. To address the influence of tactile deprivation on adult behavior, we performed bilateral whisker trimming in mice for 10 days after birth (BWT10 mice) and examined social behaviors, tactile discrimination, and c-Fos expression, a marker of neural activation, in adults after full whisker regrowth. Adult BWT10 mice exhibited significantly shorter crossable distances in the gap-crossing test than age-matched controls, indicating persistent deficits in whisker-dependent tactile perception. In contrast to controls, BWT10 mice exhibited no preference for the social compartment containing a conspecific in the three-chamber test. Furthermore, the development of amygdala circuitry was severely affected in BWT10 mice. Based on the c-Fos expression pattern, hyperactivity was found in BWT10 amygdala circuits for processing fear/anxiety-related responses to height stress but not in circuits for processing reward stimuli during whisker-dependent cued learning. These results demonstrate that neonatal whisker trimming and concomitant whisker-dependent tactile discrimination impairment severely disturbs the development of amygdala-dependent emotional regulation. [ABSTRACT FROM AUTHOR]

Information processing in the striatum requires the postsynaptic integration of glutamatergic and dopaminergic signals, which are then relayed to the output nuclei of the basal ganglia to influence behavior. Although cellularly homogeneous in appearance, the striatum contains several rare interneuron populations which tightly modulate striatal function. Of these, cholinergic interneurons (CINs) have been recently shown to play a critical role in the control of reward-related learning; however how the striatal cholinergic network is functionally organized at the mesoscopic level and the way this organization influences striatal function remains poorly understood. Here, we systematically mapped and digitally reconstructed the entire ensemble of CINs in the mouse striatum and quantitatively assessed differences in densities, spatial arrangement and neuropil content across striatal functional territories. This approach demonstrated that the rostral portion of the striatum contained a higher concentration of CINs than the caudal striatum and that the cholinergic content in the core of the ventral striatum was significantly lower than in the rest of the regions. Additionally, statistical comparison of spatial point patterns in the striatal cholinergic ensemble revealed that only a minor portion of CINs (17%) aggregated into cluster and that they were predominantly organized in a random fashion. Furthermore, we used a fluorescence reporter to estimate the activity of over two thousand CINs in naïve mice and found that there was a decreasing gradient of CIN overall function along the dorsomedial-to-ventrolateral axis, which appeared to be independent of their propensity to aggregate within the striatum. Altogether this work suggests that the regulation of striatal function by acetylcholine across the striatum is highly heterogeneous, and that signals originating in external afferent systems may be principally determining the function of CINs in the striatum. [ABSTRACT FROM AUTHOR]

LAMP5 is member of the LAMP family of membrane proteins. In contrast to the canonical members of this protein family, LAMP1 and LAMP2, which show widespread expression in many tissues, LAMP 5 is brain specific in mice. In C. elegans, the LAMP5 ortholog UNC-46 has been suggested to act a trafficking chaperone, essential for the correct targeting of the nematode vesicular GABA-transporter UNC-47. We show here that in the mouse brain LAMP5 is expressed in subpopulations of GABAergic forebrain neurons in the striato-nigral system and the olfactory bulb. The protein was present at synaptic terminals, overlapping with the mammalian vesicular GABA-transporter VGAT. In LAMP5-deficient mice localization of the transporter was unaffected arguing against a conserved role in VGAT trafficking. Electrophysiological analyses in mutants showed alterations in short term synaptic plasticity suggesting that LAMP5 is involved in controlling the dynamics of evoked GABAergic transmission. At the behavioral level, LAMP5 mutant mice showed decreased anxiety and deficits in olfactory discrimination. Altogether, this work implicates LAMP5 function in GABAergic neurotransmission in defined neuronal subpopulations. [ABSTRACT FROM AUTHOR]

Micro-plasma is a possible alternative treatment for wound management. The effect of micro-plasma on wound healing depends on its composition and temperature. The authors previously developed a capillary-tube-based micro-plasma system that can generate micro-plasma with a high nitric oxide-containing species composition and mild working temperature. Here, the efficacy of micro-plasma treatment on wound healing in a laser-induced skin wound mouse model was investigated. A partial thickness wound was created in the back skin of each mouse and then treated with micro-plasma. Non-invasive methods, namely wound closure kinetics, optical coherence tomography (OCT), and laser Doppler scanning, were used to measure the healing efficiency in the wound area. Neo-tissue growth and the expressions of matrix metallopeptidase-3 (MMP-3) and laminin in the wound area were assessed using histological and immunohistochemistry (IHC) analysis. The results show that micro-plasma treatment promoted wound healing. Micro-plasma treatment significantly reduced the wound bed region. The OCT images and histological analysis indicates more pronounced tissue regrowth in the wound bed region after micro-plasma treatment. The laser Doppler images shows that micro-plasma treatment promoted blood flow in the wound bed region. The IHC results show that the level of laminin increased in the wound bed region after micro-plasma treatment, whereas the level of MMP-3 decreased. Based on these results, micro-plasma has potential to be used to promote the healing of skin wounds clinically. [ABSTRACT FROM AUTHOR]