Mouse strain differences in autonomic responses to stress

Inter- and transgenerational heritability of preconception chronic stress or alcohol exposure: Translational outcomes in brain and behavior

Chronic stress and alcohol (ethanol) use are highly interrelated and can change an individual's behavior through molecular adaptations that do not change the DNA sequence, but instead change gene expression. A recent wealth of research has found that these nongenomic changes can be transmitted across generations, which could partially account for the "missing heritability" observed in genome-wide association studies of alcohol use disorder and other stress-related neuropsychiatric disorders. In this review, we summarize the molecular and behavioral outcomes of nongenomic inheritance of chronic stress and ethanol exposure and the germline mechanisms that could give rise to this heritability. In doing so, we outline the need for further research to: (1) Investigate individual germline mechanisms of paternal, maternal, and biparental nongenomic chronic stress- and ethanol-related inheritance; (2) Synthesize and dissect cross-generational chronic stress and ethanol exposure; (3) Determine cross-generational molecular outcomes of preconception ethanol exposure that contribute to alcohol-related disease risk, using cancer as an example. A detailed understanding of the cross-generational nongenomic effects of stress and/or ethanol will yield novel insight into the impact of ancestral perturbations on disease risk across generations and uncover actionable targets to improve human health.

The hole-board apparatus in the study of anxiety

Anxiety disorders pose a significant challenge in contemporary society, and their impact in terms of social and economic burden is overwhelming. Behavioral research conducted on animal subjects is crucial for comprehending these disorders and, from a translational standpoint, for introducing innovative therapeutic approaches. In this context, the Hole-Board apparatus has emerged as a widely utilized test for studying anxiety-related behaviors in rodents. Although a substantial body of literature underscores the utility and reliability of the Hole-Board in anxiety research, recent decades have witnessed a range of studies that have led to uncertainties and misinterpretations regarding the validity of this behavioral assay. The objective of this review is twofold: firstly, to underscore the utility and reliability of the Hole-Board assay, and concurrently, to examine the underlying factors contributing to potential misconceptions surrounding its utilization in the study of anxiety and anxiety-related behaviors. We will present results from both conventional quantitative analyses and multivariate approaches, while referencing a comprehensive collection of studies conducted using the Hole-Board.

Experimenter familiarization is a crucial prerequisite for assessing behavioral outcomes and reduces stress in mice not only under chronic pain conditions

Rodent behavior is affected by different environmental conditions. These do not only comprise experimental and housing conditions but also familiarization with the experimenter. However, specific effects on pain-related behavior and chronic pain conditions have not been examined. Therefore, we aimed to investigate the impact of different housing conditions, using individually ventilated and standard open top cages, inverted day-night cycles, and experimenter familiarization on male mice following peripheral neuropathy using the spared nerve injury (SNI) model. Using a multimodal approach, we evaluated evoked pain-related- using von Frey hair filaments, measured gait pattern with the CatWalk system, assessed anxiety- and depression-like behavior with the Elevated plus maze and tail suspension test, measured corticosterone metabolite levels in feces and utilized an integrative approach for relative-severity-assessment. Mechanical sensitivity differed between the cage systems and experimenter familiarization and was affected in both sham and SNI mice. Experimenter familiarization and an inverted day-night cycle reduced mechanical hypersensitivity in SNI and sham mice. SNI mice of the inverted day-night group displayed the slightest pronounced alterations in gait pattern in the Catwalk test. Anxiety-related behavior was only found in SNI mice of experimenter-familiarized mice compared to the sham controls. In addition, familiarization reduced the stress level measured by fecal corticosteroid metabolites caused by the pain and the behavioral tests. Although no environmental condition significantly modulated the severity in SNI mice, it influenced pain-affected phenotypes and is, therefore, crucial for designing and interpreting preclinical pain studies. Moreover, environmental conditions should be considered more in the reporting guidelines, described in more detail, and discussed as a potential influence on pain phenotypes.

Identification of therapeutic targets in a murine model of severe exertional heat stroke

Exertional heat stroke (EHS) is a potentially lethal condition resulting from high core body temperatures (TC) in combination with a systemic inflammatory response syndrome (SIRS) with varying degrees of severity across victims, and limited understanding of the underlying mechanism(s). We established a mouse model of severe EHS to identify mechanisms of hyperthermia/inflammation that may be responsible for organ damage. Mice were forced to run on a motorized wheel in a 37.5°C chamber until loss of consciousness and were either removed immediately (exertional heat injury or EHI; TCMax = 42.4 ± 0.2°C) or remained in the chamber an additional 20 min (EHS; TCMax = 42.5 ± 0.4°C). Exercise control mice (ExC) experienced identical procedures to EHS at 25°C. At 3 h post-EHS, there was evidence for an immune/inflammatory response as elevated blood chemokine [interferon γ-induced protein 10 (IP-10), keratinocytes-derived chemokine (KC), macrophage inflammatory proteins (MIP-1α), MIP-1β, MIP-2] and cytokine [granulocyte colony-stimulating factor (G-CSF), interleukins (IL-10), IL-6] levels peaked and were highest in EHS mice compared with EHI and ExC mice. Immunoblotting of organs susceptible to EHS damage indicated that several kinases were sensitive to stress associated with heat/inflammation and exercise; specifically, phosphorylation of liver c-Jun NH2-terminal kinase (JNK) at threonine 183/tyrosine 185 immediately (0 h) postheating related to heat illness severity. We have established a mouse EHS model, and JNK [or its downstream target(s)] could underlie EHS symptomatology, allowing the identification of molecular pathways or countermeasure targets to mitigate heat illness severity, enable complete recovery, and decrease overall EHS-related fatalities.

Effect of Different Ambient Temperatures on Reproductive Outcome and Stress Level of Lactating Females in Two Mouse Strains

Simple Summary

The optimal temperature for laboratory mice has been under discussion for some time. Current standard temperature is 20 °C–24 °C but it has been suggested to elevate the standard to 30 °C, which is the thermoneutral zone for mice. In this study, the effect of different cage temperatures (20 °C, 25 °C, 30 °C) on reproduction and stress hormone metabolite excretion was evaluated in lactating females of two commonly used mouse strains. Pup loss was higher, and weights of mothers and pups were reduced at 30 °C compared to the lower temperatures. In addition, pups showed increased tail length at weaning under the high temperature (30 °C). There was no difference in stress hormone metabolite excretion in mice between temperature groups. We could not show any detrimental effects of the lower or higher cage temperature on stress hormone metabolite excretion, but found decreased reproductive outcome under the higher temperature.

Abstract

Ambient temperature is an important non-biotic environmental factor influencing immunological and oncological parameters in laboratory mice. It is under discussion which temperature is more appropriate and whether the commonly used room temperature in rodent facilities of about 21 °C represents a chronic cold stress or the 30 °C of the thermoneutral zone constitutes heat stress for the animals. In this study, we selected the physiological challenging period of lactation to investigate the influence of a cage temperature of 20 °C, 25 °C, and 30 °C, respectively, on reproductive performance and stress hormone levels in two frequently used mouse strains. We found that B6D2F1 hybrid mothers weaned more pups compared to C57BL/6N mothers, and that the number of weaned pups was reduced when mothers of both strains were kept at 30 °C. Furthermore, at 30 °C, mothers and pups showed reduced body weight at weaning and offspring had longer tails. Despite pronounced temperature effects on reproductive parameters, we did not find any temperature effects on adrenocortical activity in breeding and control mice. Independent of the ambient temperature, however, we found that females raising pups showed elevated levels of faecal corticosterone metabolites (FCMs) compared to controls. Peak levels of stress hormone metabolites were measured around birth and during the third week of lactation. Our results provide no evidence of an advantage for keeping lactating mice in ambient temperatures near the thermoneutral zone. In contrast, we found that a 30 °C cage temperature during lactation reduced body mass in females and their offspring and declined female reproductive performance.

Cannabidiol (CBD) drives sex-dependent impairments in omission, but has no effect on reinforcer devaluation

Habits are inflexible behaviors that persist despite changes in outcome value. While habits allow for efficient responding, neuropsychiatric diseases such as drug addiction and obsessive-compulsive disorder are characterized by overreliance on habits. Recently, the commercially popular drug cannabidiol (CBD) has emerged as a potential treatment for addictive behaviors, though it is not entirely clear how it exerts this therapeutic effect. As brain endocannabinoids play a key role in habit formation, we sought to determine how CBD modifies goal-directed behaviors and habit formation. To explore this, mice were administered CBD (20mg/kg i.p.) or vehicle as a control and trained on random interval (RI30/60) or random ratio (RR10/20) schedules designed to elicit habitual or goal-directed lever pressing, respectively. Mice were tested for habitual responding using probe trials following reinforcer-specific devaluation as well as omission trials, where mice had to withhold responding to earn rewards. We found that while CBD had little effect on operant behaviors or reward devaluation, CBD inhibited goal-directed behavior in a sex-specific and contextdependent manner during the omission task. Beyond drug treatment, we found an effect of sex throughout training, reward devaluation, and omission. This work provides evidence that CBD has no effect on habit formation in a reward devaluation paradigm. However, the omission results suggest that CBD may slow learning of novel actionoutcome contingencies or decrease goal-directed behavior. This work calls for further examination of sex-dependent outcomes of CBD treatment and highlights the importance of investigating sex effects in habit-related experiments.

Heart Rate Variability Reveals Altered Autonomic Regulation in Response to Myocardial Infarction in Experimental Animals

The analysis of beating rate provides information on the modulatory action of the autonomic nervous system on the heart, which mediates adjustments of cardiac function to meet hemodynamic requirements. In patients with myocardial infarction, alterations of heart rate variability (HRV) have been correlated to the occurrence of arrhythmic events and all-cause mortality. In the current study, we tested whether experimental rodent models of myocardial infarction recapitulate dynamics of heart rate variability observed in humans, and constitute valid platforms for understanding mechanisms linking autonomic function to the development and manifestation of cardiovascular conditions. For this purpose, HRV was evaluated in two engineered mouse lines using electrocardiograms collected in the conscious, restrained state, using a tunnel device. Measurements were obtained in naïve mice and animals at 3-∼28 days following myocardial infarction, induced by permanent coronary artery ligation. Two mouse lines with inbred and hybrid genetic background and, respectively, homozygous (Homo) and heterozygous (Het) for the MerCreMer transgene, were employed. In the naïve state, Het female and male mice presented prolonged RR interval duration (∼9%) and a ∼4-fold increased short- and long-term RR interval variability, with respect to sex-matched Homo mice. These differences were abrogated by pharmacological interventions inhibiting the sympathetic and parasympathetic axes. At 3-∼14 days after myocardial infarction, RR interval duration increased in Homo mice, but was not affected in Het animals. In contrast, Homo mice had minor modifications in HRV parameters, whereas substantial (> 50%) reduction of short- and long-term RR interval variation occurred in Het mice. Interestingly, ex vivo studies in isolated organs documented that intrinsic RR interval duration increased in infarcted vs. non-infarcted Homo and Het hearts, whereas RR interval variation was not affected. In conclusion, our study documents that, as observed in humans, myocardial infarction in rodents is associated with alterations in heart rhythm dynamics consistent with sympathoexcitation and parasympathetic withdrawal. Moreover, we report that mouse strain is an important variable when evaluating autonomic function via the analysis of HRV.

Measuring Behavior in the Home Cage: Study Design, Applications, Challenges, and Perspectives

The reproducibility crisis (or replication crisis) in biomedical research is a particularly existential and under-addressed issue in the field of behavioral neuroscience, where, in spite of efforts to standardize testing and assay protocols, several known and unknown sources of confounding environmental factors add to variance. Human interference is a major contributor to variability both within and across laboratories, as well as novelty-induced anxiety. Attempts to reduce human interference and to measure more "natural" behaviors in subjects has led to the development of automated home-cage monitoring systems. These systems enable prolonged and longitudinal recordings, and provide large continuous measures of spontaneous behavior that can be analyzed across multiple time scales. In this review, a diverse team of neuroscientists and product developers share their experiences using such an automated monitoring system that combines Noldus PhenoTyper® home-cages and the video-based tracking software, EthoVision® XT, to extract digital biomarkers of motor, emotional, social and cognitive behavior. After presenting our working definition of a "home-cage", we compare home-cage testing with more conventional out-of-cage tests (e.g., the open field) and outline the various advantages of the former, including opportunities for within-subject analyses and assessments of circadian and ultradian activity. Next, we address technical issues pertaining to the acquisition of behavioral data, such as the fine-tuning of the tracking software and the potential for integration with biotelemetry and optogenetics. Finally, we provide guidance on which behavioral measures to emphasize, how to filter, segment, and analyze behavior, and how to use analysis scripts. We summarize how the PhenoTyper has applications to study neuropharmacology as well as animal models of neurodegenerative and neuropsychiatric illness. Looking forward, we examine current challenges and the impact of new developments. Examples include the automated recognition of specific behaviors, unambiguous tracking of individuals in a social context, the development of more animal-centered measures of behavior and ways of dealing with large datasets. Together, we advocate that by embracing standardized home-cage monitoring platforms like the PhenoTyper, we are poised to directly assess issues pertaining to reproducibility, and more importantly, measure features of rodent behavior under more ethologically relevant scenarios.

Monitoring of Heart Rate and Activity Using Telemetry Allows Grading of Experimental Procedures Used in Neuroscientific Rat Models

In animal experimentation, welfare and severity assessments of all procedures applied to animals are necessary to meet legal and ethical requirements, as well as public interests. So far, the methods suggested for this purpose are time consuming and personnel intensive. Also, evidence-based biostatistical methods for this purpose are still rare. We here tested whether the classification of heart rate (HR) and activity (Act) data monitored by telemetry in the home cage by unsupervised k-means-based class-labeling and subsequent Support Vector Machine (SVM) analysis allows severity assessment and grading of experimental procedures of different domains, including surgery, injection, behavioral testing, and routine handling for maintenance. Telemetric devices were subcutaneously implanted in young adult male Crl:CD(SD) and BDIX/UImHanZtm rats. After recovery, rats were randomly subjected to different experimental procedures, i.e., handling and cage change as routine maintenance, Rat Grimace Scale, burrowing, and social interaction for welfare assessment, as well as repeated subcutaneous injections. Thereafter, rats were either intracranially implanted with electrodes or injected with tumor cells. Directly after each procedure, HR and Act were monitored by telemetry in the home cage for 4 h. Application of k-means and SVM algorithms on the obtained data sets from baseline (as no stress), cage change (exploratory Act), and intracranial surgery (as burden) measurements computed three classes described as low HR/low Act, high HR/high Act, and high HR/low Act, respectively. Validation of the SVM model by entering data from all procedures confirmed the allocation to the high HR/low Act class (burden) after surgery, which lasted longer after subcutaneous transmitter implantation than after intracranial surgery. The majority of data points from repeated injections, behavioral testing, and maintenance handling were allocated to the low HR/low Act and high HR/high Act classes. Overall, the SVM model based on HR and Act data monitored in home cage after procedures may be useful for the classification and grading of experimental procedures of different domains.

Three Pillars of Automated Home-Cage Phenotyping of Mice: Novel Findings, Refinement, and Reproducibility Based on Literature and Experience

Animal models of neurodegenerative and neuropsychiatric disorders require extensive behavioral phenotyping. Currently, this presents several caveats and the most important are: (i) rodents are nocturnal animals, but mostly tested during the light period; (ii) the conventional behavioral experiments take into consideration only a snapshot of a rich behavioral repertoire; and (iii) environmental factors, as well as experimenter influence, are often underestimated. Consequently, serious concerns have been expressed regarding the reproducibility of research findings on the one hand, and appropriate welfare of the animals (based on the principle of 3Rs-reduce, refine and replace) on the other hand. To address these problems and improve behavioral phenotyping in general, several solutions have been proposed and developed. Undisturbed, 24/7 home-cage monitoring (HCM) is gaining increased attention and popularity as demonstrating the potential to substitute or complement the conventional phenotyping methods by providing valuable data for identifying the behavioral patterns that may have been missed otherwise. In this review, we will briefly describe the different technologies used for HCM systems. Thereafter, based on our experience, we will focus on two systems, IntelliCage (NewBehavior AG and TSE-systems) and Digital Ventilated Cage (DVC®, Tecniplast)-how they have been developed and applied during recent years. Additionally, we will touch upon the importance of the environmental/experimenter artifacts and propose alternative suggestions for performing phenotyping experiments based on the published evidence. We will discuss how the integration of telemetry systems for deriving certain physiological parameters can help to complement the description of the animal model to offer better translation to human studies. Ultimately, we will discuss how such HCM data can be statistically interpreted and analyzed.

Magnetic resonance spectroscopy in the rodent brain: Experts' consensus recommendations

In vivo MRS is a non-invasive measurement technique used not only in humans, but also in animal models using high-field magnets. MRS enables the measurement of metabolite concentrations as well as metabolic rates and their modifications in healthy animals and disease models. Such data open the way to a deeper understanding of the underlying biochemistry, related disturbances and mechanisms taking place during or prior to symptoms and tissue changes. In this work, we focus on the main preclinical 1H, 31P and 13C MRS approaches to study brain metabolism in rodent models, with the aim of providing general experts' consensus recommendations (animal models, anesthesia, data acquisition protocols). An overview of the main practical differences in preclinical compared with clinical MRS studies is presented, as well as the additional biochemical information that can be obtained in animal models in terms of metabolite concentrations and metabolic flux measurements. The properties of high-field preclinical MRS and the technical limitations are also described.

Comparative analysis of the gut microbiota composition in the Cln1R151X and Cln2R207X mouse models of Batten disease and in three wild-type mouse strains

Accumulated evidence indicates that the gut microbiota affects brain function and may be altered in neurological diseases. In this study, we analyzed the gut microbiota in Cln1^R151X and Cln2^R207X mice, models of the childhood neurodegenerative disorders, infantile CLN1 and late infantile CLN2 Batten diseases. Significant alterations were found in the overall gut microbiota composition and also at the individual taxonomic ranks as compared to wild-type mice. The disease-specific alterations in the gut microbiota of Cln1^R151X and Cln2^R207X mice may contribute to the disease phenotypes observed in these mouse models. We also compared the gut microbiota composition of three wild-type mouse strains frequently used in transgenic studies: 129S6/SvEv, C57BL/6J and mixed 129S6/SvEv × C57BL/6J. Our results show that the gut microbiota of 129S6/SvEv and C57BL/6J mice differs remarkably, which likely contributes to the known, pronounced differences in behavior and disease susceptibility between these two wild-type mouse strains.

Effect of Stress on Neuroimmune Processes

PURPOSE

Psychological stress worsens many diseases, especially those with inflammatory components, such as atopic dermatitis (AD) and autism spectrum disorder (ASD), conditions that are significantly correlated in large epidemiologic studies. However, how stress contributes to these conditions is still poorly understood. This narrative review of the relevant literature advances the premise that stress affects inflammatory processes in AD and ASD via stimulation of mast cells (MCs).

METHODS

MEDLINE was searched between 1980 and 2019 using the terms allergies, atopic dermatitis, autism spectrum disorder, brain, corticotropin-releasing hormone, inflammation, hypothalamic-pituitary-adrenal axis, mast cells, neuropeptides, stress, neurotensin, and substance P.

FINDINGS

Exposure to psychological stress is associated with onset and/or exacerbation of AD and ASD. This association could be attributable to activation of MCs, which are ubiquitous in the body, including the brain, and could contribute to inflammation.

IMPLICATIONS

Understanding and addressing the connection between stress and MCs is important in clarifying the pathogenesis and developing effective treatments for diseases that worsen with stress and involve inflammation, such as AD and ASD.

Focusing attention on biological markers of acute stressor intensity: Empirical evidence and limitations

ARMARIO, A, J. Labad and R. Nadal. Focusing attention on biological markers of acute stressor intensity: empirical evidence and limitations. NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS. The availability of biological markers that objectively quantify stress is a highly relevant issue. However, experimental evidence suggests that most physiological changes elicited by emotional stressors do not reflect their intensity and are not useful for this purpose. Thus, we review experimental evidence in animals and humans about the putative validity of neuroendocrine and sympathetic/parasympathetic variables to measure stress. Plasma levels of some hormones (e.g. ACTH, glucocorticoids, prolactin and catecholamines) have been found to reflect, at least under certain conditions, the intensity of emotional stressors in animals and probably in humans. However, the temporal resolution of hormone changes is insufficient to reflect the very dynamic psychological processes taking place while experiencing stressors. Cardiovascular parameters (e.g. heart rate and blood pressure) have much better temporal resolution but their validity as markers of stressor intensity either in animals or humans is problematic. Skin conductance and pupil dilation appear to be promising. Additional and more systematic studies are needed to demonstrate the actual validity of stress-induced physiological changes to quantify stress.

Maternal stress in Shank3ex4-9 mice increases pup-directed care and alters brain white matter in male offspring

Gene-environment interactions contribute to the risk for Autism Spectrum Disorder (ASD). Among environmental factors, prenatal exposure to stress may increase the risk for ASD. To examine if there is an interaction between exposure to maternal stress and reduced dosage or loss of Shank3, wild-type (WT), heterozygous (HET) and homozygous (HOM) female mice carrying a deletion of exons four through nine of Shank3 (Shank3^ex4-9) were exposed to chronic unpredictable mild stress (CUMS) from prior to conception throughout gestation. This study examined maternal care of these dams and the white matter microstructure in the brains of their adult male offspring. Overall, our findings suggest that maternal exposure to CUMS increased pup-directed care for dams of all three genotypes. Compared to WT and HET dams, HOM dams also exhibited increased maternal care behaviors with increased time spent in the nest and reduced cage exploration, regardless of exposure to CUMS. Diffusion tensor imaging showed higher mean fractional anisotropy in the hippocampal stratum radiatum of WT and HOM male offspring from dams exposed to CUMS and HOM offspring from unexposed dams, compared to WT male offspring from unexposed dams. These data support that CUMS in Shank3-mutant dams results in subtle maternal care alterations and long-lasting changes in the white matter of the hippocampus of their offspring.

Eye region surface temperature dynamics during acute stress relate to baseline glucocorticoids independently of environmental conditions

Reactions to acute stressors are critical for survival. Yet, the challenges of assessing underlying physiological processes in the field limit our understanding of how variation in the acute stress response relates to fitness in free-living animals. Glucocorticoid secretion during acute stress can be measured from blood plasma concentrations, but each blood sample can only provide information for one point in time. Also, the number of samples that can be extracted from an individual in the field is usually limited to avoid compromising welfare. This restricts capacity for repeated assessment, and therefore temporal resolution of findings within- and between-acute stress responses - both of which are important for determining links between acute stress and fitness. Acute stress induces additional body surface temperature changes that can be measured non-invasively, and at high frequencies using thermal imaging, offering opportunities to overcome these limitations. But, this method's usefulness in the field depends on the extent that environmental conditions affect the body surface temperature response, which remains poorly understood. We assessed the relative importance of individual physiology (baseline glucocorticoid concentrations) and environmental conditions (air temperature and relative humidity) in determining the eye region surface temperature (Teye) response to acute stress, in wild blue tits (Cyanistes caeruleus) during trapping, handling and blood sampling. When controlling for between-individual baseline variation, Teye initially dropped rapidly below, and then recovered above baseline, before declining more slowly until the end of the test, 160 s after trap closure. One measure of the amplitude of this response - the size of the initial drop in Teye - was dependent on environmental conditions, but not baseline corticosterone. Whereas, two properties defining response dynamics - the timing of the initial drop, and the slope of the subsequent recovery - were related to baseline corticosterone concentrations, independently of environmental conditions. This suggests inferring the acute stress response using thermal imaging of Teye will be practical under fluctuating environmental conditions in the field.

Benefits of non-invasive methods compared to telemetry for distress analysis in a murine model of pancreatic cancer

Prospective severity assessment is legally required in many countries to ensure high-quality research along with high welfare standards for laboratory animals. Mice and rats, the most common laboratory species, are prey animals that usually suppress signs of pain and suffering. Therefore, highly sensitive readout parameters are necessary to adequately quantify distress. The present study compared the performance of different non-invasive methods in determining animal distress, such as measuring body weight, distress score, faecal corticosterone metabolites, burrowing, and nesting behaviour, with continuous monitoring of heart rate, body temperature and activity by telemetry. The distress caused by two surgical interventions was compared and the burden caused by tumour growth was described. Transmitter implantation caused higher distress than laparotomy plus carcinoma cell injection into the pancreas. Surprisingly, no significant increase in distress was observed during tumour growth. The receiver operating characteristic curve analysis revealed that some non-invasive distress-parameters, i.e., distress-score and burrowing activity, exhibited slightly better performance to quantify distress than the most suitable parameters measured by telemetry. Due to the high burden caused by the implantation of the telemetric device, the use of non-invasive methods to assess distress in laboratory animals after surgical interventions should be favoured in future studies.

Relief Following Chronic Stress Augments Spreading Depolarization Susceptibility in Familial Hemiplegic Migraine Mice

Cortical spreading depolarization (CSD) is the electrophysiological substrate of migraine aura, and a putative trigger of trigeminovascular activation and migraine headache. Many migraineurs report stress or relief after a stress triggers an attack. We tested whether various stress conditions might modulate CSD susceptibility and whether this is dependent on genetic factors. Male and female wild type and familial hemiplegic migraine type1 (FHM1) knock-in mice heterozygous for the S218L missense mutation were subjected to acute or chronic stress, or chronic stress followed by relief (36 h). Acute stress was induced by restraint and exposure to bright light and white noise (3 h). Chronic stress was induced for 28 days by two cycles of repeated exposure of mice to a rat (7 days), physical restraint (3 days), and forced swimming (3 days). Electrical CSD threshold and KCl-induced (300 mM) CSD frequency were determined in occipital cortex in vivo at the end of each protocol. Relief after chronic stress reduced the electrical CSD threshold and increased the frequency of KCl-induced CSDs in FHM1 mutants only. Acute or chronic stress without relief did not affect CSD susceptibility in either strain. Stress status did not affect CSD propagation speed, duration or amplitude. In summary, relief after chronic stress, but not acute or chronic stress alone, augments CSD in genetically susceptible mice. Therefore, enhanced CSD susceptibility may explain why, in certain patients, migraine attacks typically occur during a period of stress relief such as weekends or holidays.

Lateral hypothalamic neurotensin neurons promote arousal and hyperthermia

Sleep and wakefulness are greatly influenced by various physiological and psychological factors, but the neuronal elements responsible for organizing sleep-wake behavior in response to these factors are largely unknown. In this study, we report that a subset of neurons in the lateral hypothalamic area (LH) expressing the neuropeptide neurotensin (Nts) is critical for orchestrating sleep-wake responses to acute psychological and physiological challenges or stressors. We show that selective activation of Nts^LH neurons with chemogenetic or optogenetic methods elicits rapid transitions from non-rapid eye movement (NREM) sleep to wakefulness and produces sustained arousal, higher locomotor activity (LMA), and hyperthermia, which are commonly observed after acute stress exposure. On the other hand, selective chemogenetic inhibition of Nts^LH neurons attenuates the arousal, LMA, and body temperature (Tb) responses to a psychological stress (a novel environment) and augments the responses to a physiological stress (fasting).

A neurotensin-producing subset of neurons in the lateral hypothalamus promote arousal and thermogenesis; these neurons are necessary for appropriate sleep-wake and body temperature responses to various stressors.

Adjusting sleep-wake behavior in response to environmental and physiological challenges may not only be of protective value, but can also be vital for the survival of the organism. For example, while it is crucial to increase wake to explore a novel environment to search for potential threats and food sources, it is also necessary to decrease wake and reduce energy expenditure during prolonged absence of food. In this study, we report that a subset of neurons in the lateral hypothalamic area (LH) expressing the neuropeptide neurotensin (Nts) is critical for orchestrating sleep-wake responses to such challenges. We show that brief activation of Nts^LH neurons in mice evokes immediate arousals from sleep, while their sustained activation increases wake, locomotor activity, and body temperature for several hours. In contrast, when Nts^LH neurons are inhibited, mice are neither able to sustain wake in a novel environment nor able to reduce wake during food deprivation. These data suggest that Nts^LH neurons may be necessary for generating appropriate sleep-wake responses to a wide variety of environmental and physiological challenges.

Antidepressant but Not Prophylactic Ketamine Administration Alters Calretinin and Calbindin Expression in the Ventral Hippocampus

Ketamine has been found to have rapid, long-lasting antidepressant effects in treatment-resistant (TR) patients with major depressive disorder (MDD). Recently, we have also shown that ketamine acts as a prophylactic to protect against the development of stress-induced depressive-like behavior in mice, indicating that a preventative treatment against mental illness using ketamine is possible. While there is significant investigation into ketamine’s antidepressant mechanism of action, little is known about ketamine’s underlying prophylactic mechanism. More specifically, whether ketamine’s prophylactic action is molecularly similar to or divergent from its antidepressant action is entirely unknown. Here, we sought to characterize immunohistochemical signatures of cell populations governing ketamine’s antidepressant and prophylactic effects. 129S6/SvEv mice were treated with saline (Sal) or ketamine (K) either before a social defeat (SD) stressor as a prophylactic, or after SD as an antidepressant, then subsequently assessed for depressive-like behavior. Post-fixed brains were processed for doublecortin (DCX), calretinin (CR) and calbindin (CB) expression. The number of DCX⁺ neurons in the dentate gyrus (DG) of the hippocampus (HPC) was not affected by prophylactic or antidepressant ketamine treatment, while the number of CR⁺ neurons in the ventral hilus increased with antidepressant ketamine under SD conditions. Moreover, antidepressant, but not prophylactic ketamine administration significantly altered CR and CB expression in the ventral HPC (vHPC). These data show that while antidepressant ketamine treatment mediates some of its effects via adult hippocampal markers, prophylactic ketamine administration does not, at least in 129S6/SvEv mice. These data suggest that long-lasting behavioral effects of prophylactic ketamine are independent of hippocampal DCX, CR and CB expression in stress-susceptible mice.

Paternal Preconception Chronic Variable Stress Confers Attenuated Ethanol Drinking Behavior Selectively to Male Offspring in a Pre-Stress Environment Dependent Manner

Stress-related psychiatric disorders such as major depression are strongly associated with alcohol abuse and alcohol use disorder. Recently, many epidemiological and preclinical studies suggest that chronic stress prior to conception has cross-generational effects on the behavior and physiological response to stress in subsequent generations. Thus, we hypothesized that chronic stress may also affect ethanol drinking behaviors in the next generation. In the first cohort of mice, we found that paternal preconception chronic variable stress significantly reduced both two-bottle choice and binge-like ethanol drinking selectively in male offspring. However, these results were not replicated in a second cohort that were tested under experimental conditions that were nearly identical, except for one notable difference. Cohort 1 offspring were derived from in-house C57BL/6J sires that were born in the animal vivarium at the University of Pittsburgh whereas cohort 2 offspring were derived from C57BL/6J sires shipped directly from the vendor. Therefore, a third cohort that included both in-house and vendor born sires was analyzed. Consistent with the first two cohorts, we observed a significant interaction between chronic stress and sire-source with only stressed sires that were born in-house able to impart reduced ethanol drinking behaviors to male offspring. Overall, these results demonstrate that paternal preconception stress can impact ethanol drinking behavior in males of the next generation. These studies provide additional support for a recently recognized role of the paternal preconception environment in shaping ethanol drinking behavior.

Zebrafish models for personalized psychiatry: Insights from individual, strain and sex differences, and modeling gene x environment interactions

Currently becoming widely recognized, personalized psychiatry focuses on unique physiological and genetic profiles of patients to best tailor their therapy. However, the role of individual differences, as well as genetic and environmental factors, in human psychiatric disorders remains poorly understood. Animal experimental models are a valuable tool to improve our understanding of disease pathophysiology and its molecular mechanisms. Due to high reproduction capability, fully sequenced genome, easy gene editing, and high genetic and physiological homology with humans, zebrafish (Danio rerio) are emerging as a novel powerful model in biomedicine. Mounting evidence supports zebrafish as a useful model organism in CNS research. Robustly expressed in these fish, individual, strain, and sex differences shape their CNS responses to genetic, environmental, and pharmacological manipulations. Here, we discuss zebrafish as a promising complementary translational tool to further advance patient-centered personalized psychiatry.

Serotonin inputs to the dorsal BNST modulate anxiety in a 5-HT1A receptor-dependent manner

Serotonin (5-HT) neurons project from the raphe nuclei throughout the brain where they act to maintain homeostasis. Here, we study 5-HT inputs into the bed nucleus of the stria terminalis (BNST), a major subdivision of the extended amygdala that has been proposed to regulate responses to anxiogenic environments in humans and rodents. While the dorsal part of the BNST (dBNST) receives dense 5-HT innervation, whether and how 5-HT in the dBNST normally modulates anxiety remains unclear. Using optogenetics, we demonstrate that activation of 5-HT terminals in the dBNST reduces anxiety in a highly anxiogenic environment. Further analysis revealed that optogenetic inhibition of 5-HT inputs into the dBNST increases anxiety in a less anxiogenic environment. We found that 5-HT predominantly hyperpolarizes dBNST neurons, reducing their activity in a manner that can be blocked by a 5-HT_1A antagonist. Finally, we demonstrate that activation of 5-HT_1A receptors in the dBNST is necessary for the anxiolytic effect observed following optogenetic stimulation of 5-HT inputs into the dBNST. These data reveal that 5-HT release in the dBNST modulates anxiety-like behavior via 5-HT_1A receptors under naturalistic conditions.

Evaluation of the neutrophil:lymphocyte ratio as an indicator of chronic distress in the laboratory mouse

When evaluating the effect of husbandry and biomethodologies on the well-being of laboratory mice, it is critical to utilize measurements that allow the distinguishing of acute stress from chronic stress. One of the most common measurements of stress in laboratory animals is the corticosterone assessment. However, while this measurement provides a highly accurate reflection of the animal's response to acute stressors, its interpretation is more prone to error when evaluating the effect of chronic stress. This study evaluated the use of the neutrophil:lymphocyte (NE:LY) ratio as an assessment of chronic stress in male and female C57Bl/6N mice as compared to serum corticosterone. One group of mice was exposed to mild daily stressors for 7 days, while the control group was handled with normal husbandry. The NE:LY ratio and serum corticosterone levels were significantly elevated in the chronically stressed mice, though a significant increase in corticosterone was only significant in males when compared by sex. The chronically stressed mice also demonstrated significantly fewer entries into the open arms and less time spent in the open arms of the elevated plus maze, suggesting that the mild daily stressors had induced a state of distress. The findings of this study confirm that the NE:LY ratio is a valid measurement for chronic stress in the laboratory mouse. However, these assays do not distinguish between distress or eustress, so behavioral and physiological assessments should always be included to determine a complete assessment of the well-being of the mouse.

Standardization of methods to record Vagus nerve activity in mice

Background

The vagus nerve plays an important role in the regulation of organ function, including reflex pathways that regulate immunity and inflammation. Recent studies using genetically modified mice have improved our understanding of molecular mechanisms in the neural control of immunity. However, mapping neural signals transmitted in the vagus nerve in mice has been limited by technical challenges. Here, we have standardized an experimental protocol to record compound action potentials transmitted in the vagus nerve.

Methods

The vagus nerve was isolated in Balb/c and B6.129S mice, and placed either on a hook or cuff electrode. The electrical signals from the vagus nerve were digitized using either a Neuralynx or Plexon data acquisition system. Changes in the vagus nerve activity in response to anesthesia, feeding and administration of bacterial endotoxin were analyzed.

Results

We have developed an electrophysiological recording system to record compound action potentials from the cervical vagus nerve in mice. Cuff electrodes significantly reduce background noise and increase the signal to noise ratio as compared to hook electrodes. Baseline vagus nerve activity varies in response to anesthesia depth and food intake. Analysis of vagus neurograms in different mouse strains (Balb/c and C57BL/6) reveal no significant differences in baseline activity. Importantly, vagus neurogramactivity in wild type and TLR4 receptor knock out mice exhibits receptor dependency of endotoxin mediated signals.

Conclusions

These methods for recording vagus neurogram in mice provide a useful tool to further delineate the role of vagus neural pathways in a standardized murine disease model.

Behavioural characterization of C57BL/6N and BALB/c female mice in social home cage - Effect of mixed housing in complex environment

Developing reliable mouse models for social behaviour is challenging. Different tests have been proposed, but most of them consist of rather artificial confrontations of unfamiliar mice in novel arenas or are relying on social stress induced by aggressive conspecifics. Natural social interaction in home cage in laboratory has not been investigated well. IntelliCage is a fully automated home-cage system, where activity of the group-housed mice can be monitored along with various cognitive tasks. Here we report the behavioural profile of C57BL/6N (B6) and BALB/c (BALB) female mice in IntelliCage when separated by strain, followed by monitoring of activity and formation of 'home-base' after mixing two strains. For that purpose, 3 cages were connected. Significant differences between the strains were established in baseline behaviour in conventional tests and in IntelliCage. The B6 mice showed reduced anxiety-like behaviour in open field and light-dark box, slightly enhanced exploratory activity in IntelliCage during initial adaptation and clearly distinct circadian activity. Mixing of two strains resulted in reduction of body weight and anhedonia in B6 mice. In addition, the B6 mice showed clear preference to previous home-cage, and formed a new home-base faster than BALB mice. In contrast, BALB mice showed enhanced activity and moving between the cages without showing any preference to previous home-cage. It could be argued that social challenge caused changes in both strains and different coping styles are responsible for behavioural manifestations. Altogether, this approach could be useful in modelling and validating mouse models for disorders with disturbed social behaviour.

Behavioral methods to study anxiety in rodents

Stress is a precipitating factor for anxiety-related disorders, which are among the leading forms of psychiatric illness and impairment in the modern world. Rodent-based behavioral tests and models are widely used to understand the mechanisms by which stress triggers anxiety-related behaviors and to identify new treatments for anxiety-related disorders. Although substantial progress has been made and many of the key neural circuits and molecular pathways mediating stress responsiveness have been characterized, these advances have thus far failed to translate into fundamentally new treatments that are safer and more efficacious in humans. The purpose of this article is to describe methods that have been historically used for this type of research and to highlight new approaches that align with recent conceptualizations of disease symptomatology and that may ultimately prove to be more fruitful in facilitating the development of improved therapeutics.

Effects of Optogenetic inhibition of BLA on Sleep Brief Optogenetic Inhibition of the Basolateral Amygdala in Mice Alters Effects of Stressful Experiences on Rapid Eye Movement Sleep

Study Objectives

Stressful events can directly produce significant alterations in subsequent sleep, in particular rapid eye movement sleep (REM); however, the neural mechanisms underlying the process are not fully known. Here, we investigated the role of the basolateral nuclei of the amygdala (BLA) in regulating the effects of stressful experience on sleep.

Methods

We used optogenetics to briefly inhibit glutamatergic cells in BLA during the presentation of inescapable footshock (IS) and assessed effects on sleep, the acute stress response, and fear memory. c-Fos expression was also assessed in the amygdala and the medial prefrontal cortex (mPFC), both regions involved in coping with stress, and in brain stem regions implicated in the regulation of REM.

Results

Compared to control mice, peri-shock inhibition of BLA attenuated an immediate reduction in REM after IS and produced a significant overall increase in REM. Moreover, upon exposure to the shock context alone, mice receiving peri-shock inhibition of BLA during training showed increased REM without altered freezing (an index of fear memory) or stress-induced hyperthermia (an index of acute stress response). Inhibition of BLA during REM under freely sleeping conditions enhanced REM only when body temperature was high, suggesting the effect was influenced by stress. Peri-shock inhibition of BLA also led to elevated c-Fos expression in the central nucleus of the amygdala and mPFC and differentially altered c-Fos activity in the selected brain stem regions.

Conclusions

Glutamatergic cells in BLA can modulate the effects of stress on REM and can mediate effects of fear memory on sleep that can be independent of behavioral fear.

Implementation of Humane Endpoints in a Urinary Bladder Carcinogenesis Study in Rats

BACKGROUND/AIM

This study aimed to evaluate the utility of several biological parameters for the prediction of tumor development and animal welfare in a rat model of urinary bladder cancer.

MATERIALS AND METHODS

The control group (n=9) received tap water while the test group (n=12) received the carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in drinking water. A score sheet with biological variables was used to monitor animals' welfare. Body weight, food and drink consumption and rectal temperature were measured weekly. Blood and urine samples were collected.

RESULTS

Animals from the control group exhibited a slightly higher body weight and body weight gain. The final urine volume was higher in BBN group (p<0.05). All animals from the BBN group exhibited macroscopic hematuria at 35th week. Four animals were anemic in the last week of the experiment.

CONCLUSION

The routine control of hematuria was a useful non-invasive biomarker of disease progression that may be used as a potential earlier humane endpoint. Animals did not show clinical signs of suffering that justified their sacrifice before the end of the study.

Insulin-like growth factor 1 receptor regulates hypothermia during calorie restriction

When food resources are scarce, endothermic animals can lower core body temperature (T_b). This phenomenon is believed to be part of an adaptive mechanism that may have evolved to conserve energy until more food becomes available. Here, we found in the mouse that the insulin-like growth factor 1 receptor (IGF-1R) controls this response in the central nervous system. Pharmacological or genetic inhibition of IGF-1R enhanced the reduction of temperature and of energy expenditure during calorie restriction. Full blockade of IGF-1R affected female and male mice similarly. In contrast, genetic IGF-1R dosage was effective only in females, where it also induced transient and estrus-specific hypothermia in animals fed ad libitum. These effects were regulated in the brain, as only central, not peripheral, pharmacological activation of IGF-1R prevented hypothermia during calorie restriction. Targeted IGF-1R knockout selectively in forebrain neurons revealed that IGF signaling also modulates calorie restriction-dependent T_b regulation in regions rostral of the canonical hypothalamic nuclei involved in controlling body temperature. In aggregate, these data identify central IGF-1R as a mediator of the integration of nutrient and temperature homeostasis. They also show that calorie restriction, IGF-1R signaling, and body temperature, three of the main regulators of metabolism, aging, and longevity, are components of the same pathway.

Comparative study of the immunological characteristics of three different C57BL/6N mouse substrains

Inbred mice, a systematically developed homogeneous animal, have been developed to maintain experimental reproducibility and to minimize experimental variables in animal-based studies. In particular, C57BL/6 mice are frequently used in experiments into immunology and antitumor activity experiments. This study was compared the immunological characteristics of C57BL/6NKorl, a Korean developed experimental animal resource, with those of two other C57BL/6N substrains. Mouse body, thymus, and spleen weights in C57BL/6NKorl were not significantly different from those of the other two C57BL/6N substrains. Among the three substrains, there was no difference in the distribution of T and B cells, which are lymphocytes involved in adaptive immunity, and no difference in NK cells related to innate immunity. Results for macrophages and granulocytes, which have roles in innate immunity, were similar in all three substrains. In order to investigate the expressions of major histocompatibility complex (MHC) molecules and allogenic antigens, splenocytes were separated from obtained spleen and analyzed by using flow cytometry. MHC class I and II molecules, which are important during self/non-self-discrimination, were similar in the three substrains. In addition, expression of alloantigen involved in allografts showed similar results in the three substrain. Thus, the results of this study provide strong evidence that C57BL/6NKorl is immunologically similar to two other C57BL/6N substrains.

Use of C57BL/6N mice on the variety of immunological researches

Inbred mice are an essential animal strain for research as they can improve the reproducibility and reliability of study results. The establishment of new inbred lines is continuing, and new inbred lines are being used in many research fields. C57BL/6 is a mouse laboratory animal that has been developed and used as an inbred strain since early stage of mouse strain development, and, in the 1950s, C57BL/6 was separated into substrains by the Jackson Laboratory (C57BL/6J) and the National Institutes of Health (C57BL/6N). C57BL/6 mice have been used in immunology and antitumor activity studies since the early strain development stage. After the mouse genome was fully described, C57BL/6 mice use in many areas of research has expanded. In particular, immunological characteristics such as those related to cell-mediated immunity and NK cell activity are relatively higher in C57BL/6 mice than in other mice. The C57BL/6NKorl is a stock of C57BL/6N established as part of a localization of experimental animal strategy of the Korean Food and Drug Administration. Based on analysis of single nucleotide polymorphisms (SNPs), C57BL/6NKorl is considered a genetically distinct inbred stock from other C57BL/6N. Various research efforts have been made to describe the characteristics and increase knowledge of the characteristics of C57BL/6Nkorl. The results obtained through these efforts are expected to increase the utilization of C57BL/6Nkorl as a domestic laboratory animal resource and to enhance the reliability of mouse based studies.

Comparison of humoral and cell-mediated immunity in three different C57BL/6N mouse substrains

Adaptive immunity is a type of immune response mediated by T and B cells, and is important response for immune response amplification and memory. In this study, the adaptive immunologic properties of C57BL/6NKorl substrain were compared with those of two other C57BL/6N substrains. There were no significant differences between the C57BL/6NKorl and the two other C57BL/6N substrains in the histological structures of the thymus and spleen, which are immunologic organs containing T cell and B cells. In addition, flow cytometric analysis did not reveal any significant differences in the distribution of T and B cell populations of the three substrains. To evaluate cell-mediated immunity of T cells in the three different substrains, we treated isolated T cells from spleen with Con A. The T cells of C57BL/6NKorl showed Con A-dependent proliferation of T cells at lower cell number than those in T cells from the other two C57BL/6N substrains. B cell-mediated humoral immune responses were not significant different among the three substrains. Thus, the results of this study provide evidence that C57BL/6NKorl mice are similar to those two other C57BL/6N substrains in humoral immunity, but C57BL/6NKorl has stronger response in cell mediated immunity.

Acoustic startle modification as a tool for evaluating auditory function of the mouse: Progress, pitfalls, and potential

Acoustic startle response (ASR) modification procedures, especially prepulse inhibition (PPI), are increasingly used as behavioral measures of auditory processing and sensorimotor gating in rodents due to their perceived ease of implementation and short testing times. In practice, ASR and PPI procedures are extremely variable across animals, experimental setups, and studies, and the interpretation of results is subject to numerous caveats and confounding influences. We review considerations for modification of the ASR using acoustic stimuli, and we compare the sensitivity of PPI procedures to more traditional operant psychoacoustic techniques. We also discuss non-auditory variables that must be considered. We conclude that ASR and PPI measures cannot substitute for traditional operant techniques due to their low sensitivity. Additionally, a substantial amount of pilot testing must be performed to properly optimize an ASR modification experiment, negating any time benefit over operant conditioning. Nevertheless, there are some circumstances where ASR measures may be the only option for assessing auditory behavior, such as when testing mouse strains with early-onset hearing loss or learning impairments.

Relaxin-3/RXFP3 signalling in mouse hypothalamus: no effect of RXFP3 activation on corticosterone, despite reduced presynaptic excitatory input onto paraventricular CRH neurons in vitro

Relaxin-3/RXFP3 signalling is proposed to be involved in the neuromodulatory control of arousal- and stress-related neural circuits. Furthermore, previous studies in rats have led to the proposal that relaxin-3/RXFP3 signalling is associated with activation of the hypothalamic-pituitary-adrenal axis, but direct evidence for RXFP3-related actions on the activity of hypothalamic corticotropin-releasing hormone (CRH) neurons is lacking. In this study, we investigated characteristics of the relaxin-3/RXFP3 system in mouse hypothalamus. Administration of an RXFP3 agonist (RXFP3-A2) intra-cerebroventricularly or directly into the paraventricular nucleus of hypothalamus (PVN) of C57BL/6J mice did not alter corticosterone levels. Similarly, there were no differences between serum corticosterone levels in Rxfp3 knockout (C57BL/6J^RXFP3TM1) and wild-type mice at baseline and after stress, despite detection of the predicted stress-induced increases in serum corticosterone. We examined the nature of the relaxin-3 innervation of PVN in wild-type mice and in Crh-IRES-Cre;Ai14 mice that co-express the tdTomato fluorophore in CRH neurons, identifying abundant relaxin-3 fibres in the peri-PVN region, but only sparse fibres associated with densely packed CRH neurons. In whole-cell voltage-clamp recordings of tdTomato-positive CRH neurons in these mice, we observed a reduction in sEPSC frequency following local application of RXFP3-A2, consistent with an activation of RXFP3 on presynaptic glutamatergic afferents in the PVN region. These studies clarify the relationship between relaxin-3/RXFP3 inputs and CRH neurons in mouse PVN, with implications for the interpretation of current and previous in vivo studies and future investigations of this stress-related signalling network in normal and transgenic mice, under normal and pathological conditions.

Paternal preconception alcohol exposure imparts intergenerational alcohol-related behaviors to male offspring on a pure C57BL/6J background

While alcohol use disorder (AUD) is a highly heritable condition, the basis of AUD in families with a history of alcoholism is difficult to explain by genetic variation alone. Emerging evidence suggests that parental experience prior to conception can affect inheritance of complex behaviors in offspring via non-genomic (epigenetic) mechanisms. For instance, male C57BL/6J (B6) mice exposed to chronic intermittent vapor ethanol (CIE) prior to mating with Strain 129S1/SvImJ ethanol-naïve females produce male offspring with reduced ethanol-drinking preference, increased ethanol sensitivity, and increased brain-derived neurotrophic factor (BDNF) expression in the ventral tegmental area (VTA). In the present study, we tested the hypothesis that these intergenerational effects of paternal CIE are reproducible in male offspring on an inbred B6 background. To this end, B6 males were exposed to 6 weeks of CIE (or room air as a control) before mating with ethanol-naïve B6 females to produce ethanol (E)-sired and control (C)-sired male and female offspring. We observed a sex-specific effect, as E-sired males exhibited decreased two-bottle free-choice ethanol-drinking preference, increased sensitivity to the anxiolytic effects of ethanol, and increased VTA BDNF expression; no differences were observed in female offspring. These findings confirm and extend our previous results by demonstrating that the effects of paternal preconception ethanol are reproducible using genetically identical, inbred B6 animals.

The basolateral amygdala can mediate the effects of fear memory on sleep independently of fear behavior and the peripheral stress response

Fear conditioning associated with inescapable shock training (ST) and fearful context re-exposure (CR) alone can produce significant behavioral fear, a stress response and alterations in subsequent REM sleep. These alterations may vary among animals and are mediated by the basolateral nucleus of the amygdala (BLA). Here, we used the GABA_A agonist, muscimol (Mus), to inactivate BLA prior to CR and examined the effects on sleep, freezing and stress-induced hyperthermia (SIH). Wistar rats (n=28) were implanted with electrodes for recording sleep, data loggers for recording core body temperature, and with cannulae aimed bilaterally into BLA. After recovery, the animals were habituated to the injection procedure and baseline sleep was recorded. On experimental day 1, rats received ST (20 footshocks, 0.8mA, 0.5s duration, 60s interstimulus interval). On experimental day 7, the rats received microinjections (0.5μl) into BLA of either Mus (1.0μM; n=13) or vehicle (Veh; n=15) prior to CR (CR1). On experimental day 21, the animals experienced a second CR (CR2) without Mus. For analysis, the rats were separated into 4 groups: (Veh-vulnerable (Veh-Vul; n=8), Veh-resilient (Veh-Res; n=7), Mus-vulnerable (Mus-Vul; n=7), and Mus-resilient (Mus-Res; n=6)) based on whether or not REM was decreased, compared to baseline, during the first 4h following ST. Pre-CR1 inactivation of BLA did not alter freezing or SIH, but did block the reduction in REM in the Mus-Vul group compared to the Veh-Vul group. These data indicate that BLA is an important region for mediating the effects of fearful memories on sleep.

Distinct behavioral and epileptic phenotype differences in 129/P mice compared to C57BL/6 mice subject to intraamygdala kainic acid-induced status epilepticus

Animal models of status epilepticus are important tools to understand the pathogenesis of epileptic brain injury and evaluate potential seizure-suppressive, neuroprotective, and antiepileptogenic treatments. Focal elicitation of status epilepticus by intraamygdala kainic acid in mice produces unilateral hippocampal damage and the emergence of spontaneous recurrent seizures after a short latent period. The model has been characterized in C57BL/6, BALB/c, and SJL mice where strain-specific differences were found in the extent of hippocampal damage. 129/P mice are a common background strain for genetic models and may display unique characteristics in this model. We therefore compared responses to intraamygdala kainic acid between 129/P and C57BL/6 mice. Racine scale-scored convulsive behavior during status epilepticus was substantially lower in 129/P mice compared with that in C57BL/6 mice. Analysis of surface-recorded electroencephalogram (EEG) showed differences between strains in several frequency bands; EEG total power was greater during ictal episodes while duration of seizures was slightly shorter in 129/P mice. Histological analysis revealed similar hippocampal injury between strains, with neuronal death mainly confined to the ipsilateral CA3 subfield. Expression of genes associated with gliosis and neuroinflammatory responses was also similar between strains after seizures. Video-EEG telemetry recordings showed that 129/P mice first display spontaneous seizures within a few days of status epilepticus similar to C57BL/6 mice. However, high mortality in 129/P mice prevented a quantitative comparison of the epileptic seizure phenotypes between strains. This study defined behavioral, EEG, and histopathologic features of this mouse strain in a model increasingly useful for the study of the genetic contribution to acquired epilepsy. Intraamygdala kainic acid in 129/P mice could serve as a model of nonconvulsive status epilepticus, but long-term assessments will require model adjustment to mitigate the severity of the emergent epileptic phenotype.

Oxidative Stress Implications in the Affective Disorders: Main Biomarkers, Animal Models Relevance, Genetic Perspectives, and Antioxidant Approaches

The correlation between the affective disorders and the almost ubiquitous pathological oxidative stress can be described in a multifactorial way, as an important mechanism of central nervous system impairment. Whether the obvious changes which occur in oxidative balance of the affective disorders are a part of the constitutive mechanism or a collateral effect yet remains as an interesting question. However it is now clear that oxidative stress is a component of these disorders, being characterized by different aspects in a disease-dependent manner. Still, there are a lot of controversies regarding the relevance of the oxidative stress status in most of the affective disorders and despite the fact that most of the studies are showing that the affective disorders development can be correlated to increased oxidative levels, there are various studies stating that oxidative stress is not linked with the mood changing tendencies. Thus, in this minireview we decided to describe the way in which oxidative stress is involved in the affective disorders development, by focusing on the main oxidative stress markers that could be used mechanistically and therapeutically in these deficiencies, the genetic perspectives, some antioxidant approaches, and the relevance of some animal models studies in this context.

Individual Differences in Animal Stress Models: Considering Resilience, Vulnerability, and the Amygdala in Mediating the Effects of Stress and Conditioned Fear on Sleep

STUDY OBJECTIVES

To examine the REM sleep response to stress and fearful memories as a potential marker of stress resilience and vulnerability and to assess the role of the basolateral amygdala (BLA) in mediating the effects of fear memory on sleep.

METHODS

Outbred Wistar rats were surgically implanted with electrodes for recording EEG and EMG and with bilateral guide cannulae directed at the BLA. Data loggers were placed intraperitoneally to record core body temperature. After recovery from surgery, the rats received shock training (ST: 20 footshocks, 0.8 mA, 0.5-s duration, 60-s interstimulus interval) and afterwards received microinjections of the GABAA agonist muscimol (MUS; 1.0 μM) to inactivate BLA or microinjections of vehicle (VEH) alone. Subsequently, the rats were separated into 4 groups (VEH-vulnerable (VEH-Vul; n = 14), VEH-resilient (VEH-Res; n = 13), MUS-vulnerable (MUS-Vul; n = 8), and MUS-resilient (MUS-Res; n = 11) based on whether or not REM was decreased, compared to baseline, during the first 4 h following ST. We then compared sleep, freezing, and the stress response (stress-induced hyperthermia, SIH) across groups to determine the effects of ST and fearful context re-exposure alone (CTX).

RESULTS

REM was significantly reduced on the ST day in both VEH-Vul and MUS-Vul rats; however, post-ST MUS blocked the reduction in REM on the CTX day in the MUS-Vul group. The VEH-Res and MUS-Res rats showed similar levels of REM on both ST and CTX days. The effects of post-ST inactivation of BLA on freezing and SIH were minimal.

CONCLUSIONS

Outbred Wistar rats can show significant individual differences in the effects of stress on REM that are mediated by BLA. These differences in REM can be independent of behavioral fear and the peripheral stress response, and may be an important biomarker of stress resilience and vulnerability.

Homer2 regulates alcohol and stress cross-sensitization

An interaction exists between stress and alcohol in the etiology and chronicity of alcohol use disorders, yet a knowledge gap exists regarding the neurobiological underpinnings of this interaction. In this regard, we employed an 11-day unpredictable, chronic, mild stress (UCMS) procedure to examine for stress-alcohol cross-sensitization of motor activity as well as alcohol consumption/preference and intoxication. We also employed immunoblotting to relate the expression of glutamate receptor-related proteins within subregions of the nucleus accumbens (NAC) to the manifestation of behavioral cross-sensitization. UCMS mice exhibited a greater locomotor response to an acute injection of 2 g/kg alcohol than unstressed controls and this cross-sensitization extended to alcohol intake (0-20 percent), as well as to the intoxicating and sedative properties of 3 and 5 g/kg alcohol, respectively. Regardless of prior alcohol injection (2 g/kg), UCMS mice exhibited elevated NAC shell levels of mGlu1α, GluN2b and Homer2, as well as lower phospholipase Cβ within this subregion. GluN2b levels were also lower within the NAC core of UCMS mice. The expression of stress-alcohol locomotor cross-sensitization was associated with lower mGlu1α within the NAC core and lower extracellular signal-regulated kinase activity within both NAC subregions. As Homer2 regulates alcohol sensitization, we assayed also for locomotor cross-sensitization in Homer2 wild-type (WT) and knock-out (KO) mice. WT mice exhibited a very robust cross-sensitization that was absent in KO animals. These results indicate that a history of mild stress renders an animal more sensitive to the psychomotor and rewarding properties of alcohol, which may depend on neuroplasticity within NAC glutamate transmission.

Finding the most appropriate mouse model of juvenile CLN3 (Batten) disease for therapeutic studies: the importance of genetic background and gender

Mutations in the CLN3 gene cause a fatal neurodegenerative disorder: juvenile CLN3 disease, also known as juvenile Batten disease. The two most commonly utilized mouse models of juvenile CLN3 disease are Cln3-knockout (Cln3^−/−) and Cln3^Δex7/8-knock-in mice, the latter mimicking the most frequent disease-causing human mutation. To determine which mouse model has the most pronounced neurological phenotypes that can be used as outcome measures for therapeutic studies, we compared the exploratory activity, motor function and depressive-like behavior of 1-, 3- and 6-month-old Cln3^−/− and Cln3^Δex7/8-knock-in mice on two different genetic backgrounds (129S6/SvEv and C57BL/6J). Although, in many cases, the behavior of Cln3^−/− and Cln3^Δex7/8 mice was similar, we found genetic-background-, gender- and age-dependent differences between the two mouse models. We also observed large differences in the behavior of the 129S6/SvEv and C57BL/6J wild-type strains, which highlights the strong influence that genetic background can have on phenotype. Based on our results, Cln3^−/− male mice on the 129S6/SvEv genetic background are the most appropriate candidates for therapeutic studies. They exhibit motor deficits at 1 and 6 months of age in the vertical pole test, and they were the only mice to show impaired motor coordination in the rotarod test at both 3 and 6 months. Cln3^−/− males on the C57BL/6J background and Cln3^Δex7/8 males on the 129S6/SvEv background also provide good outcome measures for therapeutic interventions. Cln3^−/− (C57BL/6J) males had serious difficulties in climbing down (at 1 and 6 months) and turning downward on (at 1, 3 and 6 months) the vertical pole, whereas Cln3^Δex7/8 (129S6/SvEv) males climbed down the vertical pole drastically slower than wild-type males at 3 and 6 months of age. Our study demonstrates the importance of testing mouse models on different genetic backgrounds and comparing males and females in order to find the most appropriate disease model for therapeutic studies.

Thermal Imaging to Study Stress Non-invasively in Unrestrained Birds

Stress, a central concept in biology, describes a suite of emergency responses to challenges. Among other responses, stress leads to a change in blood flow that results in a net influx of blood to key organs and an increase in core temperature. This stress-induced hyperthermia is used to assess stress. However, measuring core temperature is invasive. As blood flow is redirected to the core, the periphery of the body can cool. This paper describes a protocol where peripheral body temperature is measured non-invasively in wild blue tits (Cyanistes caeruleus) using infrared thermography. In the field we created a set-up bringing the birds to an ideal position in front of the camera by using a baited box. The camera takes a short thermal video recording of the undisturbed bird before applying a mild stressor (closing the box and therefore capturing the bird), and the bird’s response to being trapped is recorded. The bare skin of the eye-region is the warmest area in the image. This allows an automated extraction of the maximum eye-region temperature from each image frame, followed by further steps of manual data filtering removing the most common sources of errors (motion blur, blinking). This protocol provides a time series of eye-region temperature with a fine temporal resolution that allows us to study the dynamics of the stress response non-invasively. Further work needs to demonstrate the usefulness of the method to assess stress, for instance to investigate whether eye-region temperature response is proportional to the strength of the stressor. If this can be confirmed, it will provide a valuable alternative method of stress assessment in animals and will be useful to a wide range of researchers from ecologists, conservation biologists, physiologists to animal welfare researchers.

Effects of corticotropin releasing factor (CRF) on sleep and temperature following predictable controllable and uncontrollable stress in mice

Corticotropin releasing factor (CRF) is a major mediator of central nervous system responses to stressors, including alterations in wakefulness and sleep. However, its role in mediating stress-induced alterations in sleep has not been fully delineated. In this study, we assessed the role of CRF and the non-specific CRF antagonist, astressin (AST), in regulating changes in sleep produced by signaled, escapable shock (SES) and signaled inescapable shock (SIS), two stressors that can increase or decrease sleep, respectively. Male BALB/cJ mice were surgically implanted with transmitters (DataSciences ETA10-F20) for recording EEG, activity and core body temperature by telemetry and a cannula for intracerebroventricular (ICV) microinjections. After baseline (Base) sleep recording, mice were presented tones (90 dB, 2 kHz) that started 5.0 s prior to and co-terminated with footshock (0.5 mA; 5.0 s maximum duration). SES mice (n = 9) always received shock but could terminate it by moving to the non-occupied chamber in a shuttlebox. Yoked SIS mice (n = 9) were treated identically, but could not alter shock duration. Training with SES or SIS was conducted over 2 days to stabilize responses. Afterwards, the mice received saline, CRF [0.4 μg (0.42 mM) or AST (1.0 μg (1.4 mM)] prior to SES or SIS. Sleep was analyzed over 20 h post-stress recordings. After administration of saline, REM was significantly greater in SES mice than in SIS mice whereas after CRF or AST, REM was similar in both groups. Total 20 h NREM did not vary across condition or group. However, after administration of saline and CRF, NREM episode duration was significantly decreased, and NREM episode number significantly increased, in SIS mice compared to SES animals. SES and SIS mice showed similar stress induced hyperthermia (SIH) across all conditions. These data demonstrate that CRF can mediate stress-induced changes in sleep independently of SIH, an index of hypothalamic-pituitary-adrenal axis activation.

Effect of crossing C57BL/6 and FVB mouse strains on basal cytokine expression

C57BL/6 is the most often used laboratory mouse strain. However, sometimes it is beneficial to cross the transgenic mice on the C57BL/6 background to the other strain, such as FVB. Although this is a common strategy, the influence of crossing these different strains on homeostatic expression of cytokines is not known. Here we have investigated the differences in the expression of selected cytokines between C57BL/6J and C57BL/6JxFVB mice in serum and skeletal muscle. We have found that only few cytokines were altered by crossing of the strains. Concentrations of IL5, IL7, LIF, MIP-2, and IP-10 were higher in serum of C57BL/6J mice than in C57BL/6JxFVB mice, whereas concentration of G-CSF was lower in C57BL/6J. In the skeletal muscle only the concentration of VEGF was higher in C57BL/6J mice than in C57BL/6JxFVB mice. Concluding, the differences in cytokine expression upon crossing C57BL/6 and FVB strain in basal conditions are not profound.

Comparative biochemical characterization of the monoacylglycerol lipase inhibitor KML29 in brain, spinal cord, liver, spleen, fat and muscle tissue

Monoacylglycerol lipase (MAGL) is part of the endocannabinoid and the prostaglandin signaling system. MAGL degrades the endocannabinoid 2-arachidonoylglycerol (2-AG) into glycerol and arachidonic acid. MAGL-induced arachidonic acid is the primary source for prostaglandin synthesis in the brain. 2-AG mainly induces neuroprotective and anti-inflammatory effects, whereas prostaglandins are related to pro-inflammatory effects inducing neurotoxicity. Therefore, inhibition of MAGL represents a promising target for neurological diseases characterized by inflammation. However, as 2-AG is an agonist for the cannabinoid receptor 1 (CB1), inhibition of MAGL might be associated with unwanted cannabimimetic effects. Here, we show that oral administration of KML29, a highly selective inhibitor of MAGL, induced large and dose-dependent changes in 2-AG levels in vivo in brain and spinal cord of mice. Of note, MAGL inhibition by KML29 induced a decrease in prostaglandin levels in brain and most peripheral tissues but not in the spinal cord. MAGL expression was highest in fat, liver and brain, whereas the cytosolic phospholipase A2 (cPLA2), a further enzyme responsible for arachidonic acid production, was highly expressed in spinal cord, muscle and spleen. In addition, high doses (10 mg/kg) of KML29 induced some cannabimimetic effects in vivo in the tetrad test, including hypothermia, analgesia and hypomotility without induction of cataleptic behavior. In summary, inhibition of MAGL by KML29 represents a promising strategy for targeting the cannabinoid and prostaglandin system of the brain with only a moderate induction of cannabimimetic effects.

Serotonin: a never-ending story

The neurotransmitter serotonin is an evolutionary ancient molecule that has remarkable modulatory effects in almost all central nervous system integrative functions, such as mood, anxiety, stress, aggression, feeding, cognition and sexual behavior. After giving a short outline of the serotonergic system (anatomy, receptors, transporter) the author's contributions over the last 40 years in the role of serotonin in depression, aggression, anxiety, stress and sexual behavior is outlined. Each area delineates the work performed on animal model development, drug discovery and development. Most of the research work described has started from an industrial perspective, aimed at developing animals models for psychiatric diseases and leading to putative new innovative psychotropic drugs, like in the cases of the SSRI fluvoxamine, the serenic eltoprazine and the anxiolytic flesinoxan. Later this research work mainly focused on developing translational animal models for psychiatric diseases and implicating them in the search for mechanisms involved in normal and diseased brains and finding new concepts for appropriate drugs.