Acclimatization of rats after ground transportation to a new animal facility

Evaluation of Neuro-Hormonal Dynamics after the Administration of Probiotic Microbial Strains in a Murine Model of Hyperthyroidism

The microbiota-gut-brain axis has received increasing attention in recent years through its bidirectional communication system, governed by the ability of gut microorganisms to generate and regulate a wide range of neurotransmitters in the host body. In this research, we delve into the intricate area of microbial endocrinology by exploring the dynamic oscillations in neurotransmitter levels within plasma and brain samples. Our experimental model involved inducing hyperthyroidism in mice after a "probiotic load" timeframe using two strains of probiotics (Lactobacillus acidophilus, Saccharomyces boulardii, and their combination). These probiotic interventions continued throughout the experiment and were intended to uncover potential modulatory effects on neurotransmitter levels and discern if certain probiotic strains exhibit any protection from hyperthyroidism. Moreover, we aimed to outline the eventual connections between the gut microbiota and the hypothalamus-pituitary-thyroid axis. As our study reveals, there are significant fluctuations in crucial neurotransmitters within the hyperthyroidism model, related to the specific probiotic strain or combination. These findings could support future therapeutic approaches, help healthcare professionals choose between different probiotic therapies, and also allow us proceed with caution when administering such treatments, depending on the health status of hyperthyroid patients.

Emodin, a Natural Anthraquinone, Increases Uric Acid Excretion in Rats with Potassium Oxonate-Induced Hyperuricemia

The treatment of hyperuricemia and gout is mostly based on lowering serum uric acid levels using drugs, such as allopurinol, or increasing urinary excretion of uric acid. However, some patients still experience adverse reactions to allopurinol and turn to Chinese medicine as an alternative. Therefore, it is crucial to design a preclinical study to obtain more convincing data on the treatment of hyperuricemia and gout with Chinese medicine. This study aimed to explore the therapeutic effect of emodin, a Chinese herbal extract, in a rat model of hyperuricemia and gout. In this study, we used 36 Sprague-Dawley rats, which were randomly divided into six groups for experimentation. Hyperuricemia was induced in rats by intraperitoneal injections of potassium oxonate. The efficacy of emodin in reducing serum uric acid levels was demonstrated by comparing the positive control group with groups treated with three different concentrations of emodin. The inflammatory profiles, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α levels, were unaffected by emodin treatment. In the experimental results, it was observed that the serum uric acid concentration in the vehicle control group was 1.80 ± 1.14, while the concentrations in the moderate and high concentration emodin groups were 1.18 ± 0.23 and 1.12 ± 0.57, resulting in no significant difference in uric acid concentration between these treatment groups and the control group, indicating that emodin has a therapeutic effect on hyperuricemia. The increase in the fractional excretion of uric acid (FEUA) demonstrated that emodin promoted urinary uric acid excretion without significantly affecting the inflammatory profile. Thus, emodin reduced the serum uric acid concentration to achieve effective treatment of hyperuricemia and gout by increasing urinary excretion. These results were supported by the measured serum uric acid and FEUA levels. Our data have potential implications for the treatment of gout and other types of hyperuricemia in clinical practice.

Reproductive and metabolic toxic effects of polystyrene microplastics in adult female Wistar rats: a mechanistic study

Microplastics, such as polystyrene microplastics (PS-MPs), have become an emerging environmental hazard for animals and humans. Long-term exposure to PS-MPs has led to neurotoxicity, reproductive dysfunction, and carcinogenesis. The goal of this study was to evaluate the effect of sub-chronic exposure of PS-MPs on metabolic and reproductive functions in female rats. The PS-MPs were prepared by cryogenic technique. The PS-MPs were given orally to female Wistar rats for 45 days at 2.5, 5, and 10 mg/kg/day. The average PS-MPs' size diameter was 876 nm. The PS-MPs administration resulted in a significant decrease in the activity of superoxide dismutase and catalase in the liver and ovary. The effect of PS-MPs on reduced glutathione and lipid peroxidation in the liver and ovarian tissues of rats was statistically insignificant. The PS-MP exposure exhibited an increase in the levels of triglycerides, total cholesterol, and low-density lipoprotein and decrease in high-density lipoprotein. The PS-MPs caused glucose intolerance and increase in insulin. Moreover, the PS-MP exposure increased follicle stimulating hormone, estradiol, and testosterone. Serum level of interleukin-6 and nuclear factor kappa B (NF-κB) was elevated in animals treated with PS-MPs. The PS-MP exposed rats showed normal ovarian histology, but activated hepatic stellate cells and liver fibrosis. It is concluded that the sub-chronic exposure to PS-MPs resulted in metabolic and endocrine disruption in female rats through oxidative damage, hormonal imbalance, and chronic inflammation.

Differential distribution of cholesterol pools across arteries under high-cholesterol diet

Excessive cholesterol constitutes a major risk factor for vascular disease. Within cells, cholesterol is distributed in detergent-sensitive and detergent-resistant fractions, with the largest amount of cholesterol residing in cellular membranes. We set out to determine whether various arteries differ in their ability to accumulate esterified and non-esterified cholesterol in detergent-sensitive versus detergent-resistant fractions throughout the course of a high-cholesterol diet. Male Sprague-Dawley rats were placed on 2 % cholesterol diet while a control group was receiving iso-caloric standard chow. Liver, aorta, and pulmonary, mesenteric, and cerebral arteries were collected at 2-6, 8-12, 14-18, and 20-24 weeks from the start of high-cholesterol diet. After fraction separation, esterified and free non-esterified cholesterol levels were measured. In all arteries, largest cholesterol amounts were present in detergent-sensitive fractions in the non-esterified form. Overall, cholesterol in aorta and cerebral arteries was elevated during 14-18 weeks of high-cholesterol diet. Cerebral arteries also exhibited increase in esterified cholesterol within detergent-sensitive domains, as well as increase in cholesterol level in the detergent-resistant fraction at earlier time-points of diet. Pulmonary artery and mesenteric artery were largely resistant to cholesterol accumulation. Quantitative polymerase chain reaction (qPCR) analysis revealed up-regulation of low-density lipoprotein receptor (Ldlr) and low-density lipoprotein receptor-related protein 1 (Lrp1) gene expression in cerebral arteries when compared to mesenteric and pulmonary arteries, respectively. In summary, we unveiled the differential ability of arteries to accumulate cholesterol over the course of a high-cholesterol diet. The differential accumulation of cholesterol seems to correlate with the up-regulated gene expression of proteins responsible for cholesterol uptake.

Ameliorating Effect of Malva neglecta Wallr on Obesity and Diabetes in Wistar Rats: A Mechanistic Study

A high caloric food causes deposition of fats that may progress to obesity. Obesity is a risk factor for various metabolic and cardiovascular diseases, including but limited to diabetes mellitus. This study is aimed at determining the ameliorating effect of Malva Neglecta wallr aqueous-methanolic extract (MNME) on obesity and diabetes in Wistar rats. The MNME was chemically characterized by high-performance liquid chromatography (HPLC). The plant extract was evaluated by in vitro α-amylase inhibition and DPPH scavenging activities. Obesity was induced by administering high sugar and fat diet (HSFD) to rats for six weeks, followed by intraperitoneal injection of alloxan monohydrate (150 mg/kg) to induce diabetes. Oral treatments with MNME 250, 500, and 750 mg/kg/day were given to diabetic obese rats for 14 days. The HPLC analysis showed the presence of phenolic acids and flavonoids. The plant extract showed significant antioxidant (P < 0.001) and alpha-amylase (P < 0.0001) inhibition activities. The administration of MNME displayed a considerable decrease in fasting blood glucose, body weight, liver function tests, urea, cholesterol, leptin, and insulin levels in diabetic obese rats as compared to the disease control group and maximum effect were observed at 750 mg/kg/day of MNME. The MNME significantly increased (P < 0.05 − 0.001) the levels of GSH, SOD, and CAT in the liver, kidney, and pancreas while notably (P < 0.05 − 0.001) reduced the malondialdehyde level in kidney and pancreas of diabetic obese rats in contrast to disease control rats. This experimental study concludes that the MNME had exhibited antiobesity and antidiabetic activities through reduction of oxidative stress, leptin, α-amylase activity, and insulin resistance due to the presence of phenolic acid and flavonoid compounds.

Reporting Data on Auditory Brainstem Responses (ABR) in Rats: Recommendations Based on Review of Experimental Protocols and Literature

Research in hearing science is accelerating, and a wealth of data concerning auditory brainstem responses (ABR) in various animal models is published in peer-reviewed journals every year. Recently, we reviewed studies using ABR measurements in tinnitus rat models. We found significant discrepancies in the outcomes of these studies, some due to different research approaches and others due to different methodologies. Thus, the present work aimed to collect comprehensive information on all factors influencing ABR recordings in rats and compile recommendations on ABR data reporting. A questionnaire with queries about animal husbandry, transfer, handling, and the exact test conditions before, during, and after ABR recordings was sent to 125 researchers who published the relevant studies between 2015 and 2021. Eighteen researchers provided detailed answers on factors related to ABR measurements. Based on the analysis of the returned questionnaires, we identified three domains reflecting animal-, equipment-, and experiment-dependent factors that might influence the ABR outcome, thus requiring reporting in published research. The analysis of survey results led to the compilation of recommendations for reporting ABR outcomes supported by a literature review. Following these recommendations should facilitate comparative and meta-analyses of ABR results provided by various research groups.

Micro- and Macroenvironmental Conditions and Stability of Terrestrial Models

Environmental variables can have profound effects on the biological responses of research animals and the outcomes of experiments dependent on them. Some of these influences are both predictable and unpredictable in effect, many are challenging to standardize, and all are influenced by the planning and conduct of experiments and the design and operation of the vivarium. Others are not yet known. Within the immediate environment where the research animal resides, in the vivarium and in transit, the most notable of these factors are ambient temperature, relative humidity, gaseous pollutant by-products of animal metabolism and physiology, dust and particulates, barometric pressure, electromagnetic fields, and illumination. Ambient temperatures in the animal housing environment, in particular those experienced by rodents below the thermoneutral zone, may introduce degrees of stress and thermoregulatory compensative responses that may complicate or invalidate study measurements across a broad array of disciplines. Other factors may have more subtle and specific effects. It is incumbent on scientists designing and executing experiments and staff responsible for animal husbandry to be aware of, understand, measure, systematically record, control, and account for the impact of these factors on sensitive animal model systems to ensure the quality and reproducibility of scientific studies.

Experience-Dependent c-Fos Expression in the Mediodorsal Thalamus Varies With Chemosensory Modality

The mediodorsal thalamus is a higher order thalamic nucleus critical for many cognitive behaviors. Defined by its reciprocal connections with the prefrontal cortex, the mediodorsal thalamus receives strong projections from chemosensory cortical areas for taste and smell, gustatory cortex and piriform cortex. Recent studies indicate the mediodorsal thalamus is involved in experience-dependent chemosensory processes, including olfactory attention and discrimination and the hedonic perception of odor-taste mixtures. How novel and familiar chemosensory stimuli are represented within this structure remains unclear. Here, we compared the expression of c-Fos in the mediodorsal thalami of rats familiar with an odor, a taste, or an odor-taste mixture with those that sampled the stimuli for the first time. We found that familiar tastes or odor-taste mixtures induced significantly greater c-Fos expression in the mediodorsal thalamus than novel tastes or odor-taste mixtures, whereas novel odors induced greater c-Fos expression than familiar odors. These experience-dependent and modality-specific differences in c-Fos expression may relate to the behavioral relevance of the chemosensory stimulus, including odor neophobia. In a two-bottle brief-access preference task, rats preferred water to isoamyl acetate-odorized water over multiple days. However, after experience with isoamyl acetate mixed with sucrose (odor-taste mixture), the preference for water was eliminated. These findings demonstrate that experience with chemosensory stimuli modulates responses in the mediodorsal thalamus, suggesting this structure plays an integral role in communicating behaviorally relevant chemosensory information to higher order areas to guide food-related behaviors.

Continuous measurement of locomotor activity during convalescence and acclimation in group-housed rats

Locomotor activity is affected by a range of factors in addition to experimental treatment, including the breeding environment. Appropriate convalescence and acclimation are important for animal experiments, because environmental changes and physical burden can result from surgery, transportation, and cage exchange. However, the duration that locomotor activity is affected by these factors is currently unclear, because it has traditionally been difficult to measure locomotor activity in multiple group-housed animals in any location other than the analysis room. In the present study, we analyzed the locomotor activity of group-housed rats using a nano tag^® after surgery, transportation, and cage exchange. The nano tag^®, a new device for analyzing activity, can measure locomotor activity in laboratory animals with no limitation on the number of animals in same cage. Any type of cage can be used for analysis, at any time of day, and in any location. Nano tags^® were subcutaneously implanted in male rats (F344/NSlc, 6 weeks of age) and locomotor activity was continuously measured after surgery, transportation, and cage exchange. Significant activity changes were observed in rats after transportation and cage exchange, 9 days and 3 h after the event, respectively. The results suggest that continuous measurement of locomotor activity with nano tags^® can be used to monitor changes in activity induced by environmental changes, and will be helpful for designing animal experiments analyzing locomotor activity.

Early adolescent adversity inflates threat estimation in females and promotes alcohol use initiation in both sexes

Childhood adversity is associated with exaggerated threat processing and earlier alcohol use initiation. Conclusive links remain elusive, as childhood adversity typically co-occurs with detrimental socioeconomic factors, and its impact is likely moderated by biological sex. To unravel the complex relationships among childhood adversity, sex, threat estimation, and alcohol use initiation, we exposed female and male Long-Evans rats to early adolescent adversity (EAA). In adulthood, >50 days following the last adverse experience, threat estimation was assessed using a novel fear discrimination procedure in which cues predict a unique probability of footshock: danger (p = 1.00), uncertainty (p = .25), and safety (p = .00). Alcohol use initiation was assessed using voluntary access to 20% ethanol, >90 days following the last adverse experience. During development, EAA slowed body weight gain in both females and males. In adulthood, EAA selectively inflated female threat estimation, exaggerating fear to uncertainty and safety, but promoted alcohol use initiation across sexes. Meaningful relationships between threat estimation and alcohol use initiation were not observed, underscoring the independent effects of EAA. Results isolate the contribution of EAA to adult threat estimation, alcohol use initiation, and reveal moderation by biological sex. (PsycINFO Database Record

Does the Stress of Laboratory Life and Experimentation on Animals Adversely Affect Research Data? A Critical Review

Recurrent acute and/or chronic stress can affect all vertebrate species, and can have serious consequences. It is increasingly and widely appreciated that laboratory animals experience significant and repeated stress, which is unavoidable and is caused by many aspects of laboratory life, such as captivity, transport, noise, handling, restraint and other procedures, as well as the experimental procedures applied to them. Such stress is difficult to mitigate, and lack of significant desensitisation/habituation can result in considerable psychological and physiological welfare problems, which are mediated by the activation of various neuroendocrine networks that have numerous and pervasive effects. Psychological damage can be reflected in stereotypical behaviours, including repetitive pacing and circling, and even self-harm. Physical consequences include adverse effects on immune function, inflammatory responses, metabolism, and disease susceptibility and progression. Further, some of these effects are epigenetic, and are therefore potentially transgenerational: the biology of animals whose parents/grandparents were wild-caught and/or have experienced chronic stress in laboratories could be altered, as compared to free-living individuals. It is argued that these effects must have consequences for the reliability of experimental data and their extrapolation to humans, and this may not be recognised sufficiently among those who use animals in experiments.

Using Clicker Training and Social Observation to Teach Rats to Voluntarily Change Cages

Cage cleaning is a routinely performed husbandry procedure and is known to induce stress in laboratory rats. As stress can have a negative impact on well-being and can affect the comparability and reproducibility of research results, the amount of stress experienced by laboratory animals should be minimized and avoided when possible. Further, the direct contact between the rat and animal caretaker during the cage change bears hygiene risks and therefore possibly negatively impacts the well-being of the rats and the quality of the research. Our protocol aims to improve the routinely performed cage changing procedure. For this reason, we present a feasible protocol that enables rats to learn via clicker training and observation to voluntarily change to a clean cage. This training helps to reduce stress caused by the physical disturbance and handling associated with the cage changes and concurrently enables a reduction in direct contact between animal and animal caretaker after the training phase is completed. The implementation of clicker training to rats is fast and easy. Rats are generally interested in the training and efficiently learn the desired behavior, which entails changing cages through a pipe. Even without training, the rats learn to perform the desired behavior by observation, as 80% of the observational learning group successfully changed cages when tested. The training further helps to establish a relationship of trust between trainer and animal. As hygiene and well-being are both very important in animal experiments, this protocol might also help to improve high-quality research.

Acclimation and Institutionalization of the Mouse Microbiota Following Transportation

Using animal models, the gut microbiota has been shown to play a critical role in the health and disease of many organ systems. Unfortunately, animal model studies often lack reproducibility when performed at different institutions. Previous studies in our laboratory have shown that the gut microbiota of mice can vary with a number of husbandry factors leading us to speculate that differing environments may alter gut microbiota, which in turn may influence animal model phenotypes. As an extension of these studies, we hypothesized that the shipping of mice from a mouse producer to an institution will result in changes in the type, relative abundance, and functional composition of the gut microbiota. Furthermore, we hypothesized that mice will develop a microbiota unique to the institution and facility in which they are housed. To test these hypotheses, mice of two strains (C57BL/6J and BALB/cJ), two age groups (4 week and 8 week old), and originating from two types of housing (research animal facility under conventional housing and production facilities under maximum barrier housing) were obtained from The Jackson Laboratory. Fecal samples were collected the day prior to shipping, immediately upon arrival, and then on days 2, 5, 7, and weeks 2, 4, and 9 post-arrival. Following the first post-arrival fecal collection, mice were separated into 2 groups and housed at different facilities at our institution while keeping their caging, diet, and husbandry practices the same. DNA was extracted from the collected fecal pellets and 16S rRNA amplicons were sequenced in order to characterize the type and relative abundance of gut bacteria. Principal component analysis (PCA) and permutational multivariate analysis of variance (PERMANOVA) demonstrated that both the shipping and the institution and facility in which mice were housed altered the gut microbiota. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) predicted differences in functional composition in the gut microbiota of mice based on time of acclimation.

Blockade of α2-adrenergic receptors in prelimbic cortex: impact on cocaine self-administration in adult spontaneously hypertensive rats following adolescent atomoxetine treatment

RATIONALE

Research with the spontaneously hypertensive rat (SHR) model of attention deficit/hyperactivity disorder demonstrated that chronic methylphenidate treatment during adolescence increased cocaine self-administration established during adulthood under a progressive ratio (PR) schedule. Compared to vehicle, chronic atomoxetine treatment during adolescence failed to increase cocaine self-administration under a PR schedule in adult SHR.

OBJECTIVES

We determined if enhanced noradrenergic transmission at α2-adrenergic receptors within prefrontal cortex contributes to this neutral effect of adolescent atomoxetine treatment in adult SHR.

METHODS

Following treatment from postnatal days 28-55 with atomoxetine (0.3 mg/kg) or vehicle, adult male SHR and control rats from Wistar-Kyoto (WKY) and Wistar (WIS) strains were trained to self-administer 0.3 mg/kg cocaine. Self-administration performance was evaluated under a PR schedule of cocaine delivery following infusion of the α2-adrenergic receptor antagonist idazoxan (0 and 10-56 μg/side) directly into prelimbic cortex.

RESULTS

Adult SHR attained higher PR break points and had greater numbers of active lever responses and infusions than WKY and WIS. Idazoxan dose-dependently increased PR break points and active lever responses in SHR following adolescent atomoxetine vs. vehicle treatment. Behavioral changes were negligible after idazoxan pretreatment in SHR following adolescent vehicle or in WKY and WIS following adolescent atomoxetine or vehicle.

CONCLUSIONS

α2-Adrenergic receptor blockade in prelimbic cortex of SHR masked the expected neutral effect of adolescent atomoxetine on adult cocaine self-administration behavior. Moreover, greater efficacy of acute idazoxan challenge in adult SHR after adolescent atomoxetine relative to vehicle is consistent with the idea that chronic atomoxetine may downregulate presynaptic α2A-adrenergic autoreceptors in SHR.

Monkey-based research on human disease: the implications of genetic differences

Assertions that the use of monkeys to investigate human diseases is valid scientifically are frequently based on a reported 90-93% genetic similarity between the species. Critical analyses of the relevance of monkey studies to human biology, however, indicate that this genetic similarity does not result in sufficient physiological similarity for monkeys to constitute good models for research, and that monkey data do not translate well to progress in clinical practice for humans. Salient examples include the failure of new drugs in clinical trials, the highly different infectivity and pathology of SIV/HIV, and poor extrapolation of research on Alzheimer's disease, Parkinson's disease and stroke. The major molecular differences underlying these inter-species phenotypic disparities have been revealed by comparative genomics and molecular biology - there are key differences in all aspects of gene expression and protein function, from chromosome and chromatin structure to post-translational modification. The collective effects of these differences are striking, extensive and widespread, and they show that the superficial similarity between human and monkey genetic sequences is of little benefit for biomedical research. The extrapolation of biomedical data from monkeys to humans is therefore highly unreliable, and the use of monkeys must be considered of questionable value, particularly given the breadth and potential of alternative methods of enquiry that are currently available to scientists.

EEG Radiotelemetry in Small Laboratory Rodents: A Powerful State-of-the Art Approach in Neuropsychiatric, Neurodegenerative, and Epilepsy Research

EEG radiotelemetry plays an important role in the neurological characterization of transgenic mouse models of neuropsychiatric and neurodegenerative diseases as well as epilepsies providing valuable insights into underlying pathophysiological mechanisms and thereby facilitating the development of new translational approaches. We elaborate on the major advantages of nonrestraining EEG radiotelemetry in contrast to restraining procedures such as tethered systems or jacket systems containing recorders. Whereas a main disadvantage of the latter is their unphysiological, restraining character, telemetric EEG recording overcomes these disadvantages. It allows precise and highly sensitive measurement under various physiological and pathophysiological conditions. Here we present a detailed description of a straightforward successful, quick, and efficient technique for intraperitoneal as well as subcutaneous pouch implantation of a standard radiofrequency transmitter in mice and rats. We further present computerized 3D-stereotaxic placement of both epidural and deep intracerebral electrodes. Preoperative preparation of mice and rats, suitable anaesthesia, and postoperative treatment and pain management are described in detail. A special focus is on fields of application, technical and experimental pitfalls, and technical connections of commercially available radiotelemetry systems with other electrophysiological setups.

High-fructose diet during periadolescent development increases depressive-like behavior and remodels the hypothalamic transcriptome in male rats

Fructose consumption, which promotes insulin resistance, hypertension, and dyslipidemia, has increased by over 25% since the 1970s. In addition to metabolic dysregulation, fructose ingestion stimulates the hypothalamic-pituitary-adrenal (HPA) axis leading to elevations in glucocorticoids. Adolescents are the greatest consumers of fructose, and adolescence is a critical period for maturation of the HPA axis. Repeated consumption of high levels of fructose during adolescence has the potential to promote long-term dysregulation of the stress response. Therefore, we determined the extent to which consumption of a diet high in fructose affected behavior, serum corticosterone, and hypothalamic gene expression using a whole-transcriptomics approach. In addition, we examined the potential of a high-fructose diet to interact with exposure to chronic adolescent stress. Male Wistar rats fed the periadolescent high-fructose diet showed increased anxiety-like behavior in the elevated plus maze and depressive-like behavior in the forced swim test in adulthood, irrespective of stress history. Periadolescent fructose-fed rats also exhibited elevated basal corticosterone concentrations relative to their chow-fed peers. These behavioral and hormonal responses to the high-fructose diet did not occur in rats fed fructose during adulthood only. Finally, rats fed the high-fructose diet throughout development underwent marked hypothalamic transcript expression remodeling, with 966 genes (5.6%) significantly altered and a pronounced enrichment of significantly altered transcripts in several pathways relating to regulation of the HPA axis. Collectively, the data presented herein indicate that diet, specifically one high in fructose, has the potential to alter behavior, HPA axis function, and the hypothalamic transcriptome in male rats.

CNS Adverse Effects: From Functional Observation Battery/Irwin Tests to Electrophysiology

This chapter describes various approaches for the preclinical assessment of drug-induced central nervous system (CNS) adverse effects. Traditionally, methods to evaluate CNS effects have consisted of observing and scoring behavioral responses of animals after drug is administered. Among several behavioral testing paradigms, the Irwin and the functional observational battery (FOB) are the most commonly used assays for the assessment of CNS effects. The Irwin and FOB are considered good first-tier assays to satisfy the ICH S7A guidance for the preclinical evaluation of new chemical entities (NCE) intended for humans. However, experts have expressed concern about the subjectivity and lack of quantitation that is derived from behavioral testing. More importantly, it is difficult to gain insight into potential mechanisms of toxicity by assessing behavioral outcomes. As a complement to behavioral testing, we propose using electrophysiology-based assays, both in vivo and in vitro, such as electroencephalograms and brain slice field-potential recordings. To better illustrate these approaches, we discuss the implementation of electrophysiology-based techniques in drug-induced assessment of seizure risk, sleep disruption, and cognitive impairment.

Effects of Transfer from Breeding to Research Facility on the Welfare of Rats

Simple Summary

This study measured effects of transfer on body temperature, stress hormone levels, body weight, behavior and water and food intake in rats. Environmental temperature strongly affected body temperature of rats and needs to be controlled. Male rats need to habituate for at least one week, females for two weeks after transfer.

Abstract

Transfer from the breeding facility to a research facility is a stressful event for laboratory animals. Heat stress has been reported to constitute one of the major concerns during transport of animals. This study measured ambient and body temperature, corticosterone and glucose levels, body weight, behavior and water and food intake before, during and after transfer in Wistar rats. Decreased body weight, water and food intake were observed on the day of transfer in rats. Environmental temperature strongly affected body temperature of rats and needs to be controlled. Male rats need to habituate for at least one week, females for two weeks after transfer.

Sex Differences in Physiological Acclimatization after Transfer in Wistar Rats

Simple Summary

This study in laboratory rodents shows a sex specific effect of breeder to research facility transfer on several physiological parameters, such as heart rate and blood pressure. We recommend at least 8 days of acclimatization time after transfer in male rats and at least two weeks in female rats, before using these animals in research.

Abstract

Most laboratory animals used in research are vendor-bred and transferred to research facilities. Transfer procedures might have considerable and unintended effects on research results. In the present study we compared physiological and behavioral parameters before and after external and internal transfer, as well as between transferred and non-transferred Wistar rats. The impact of both external and internal transfer on body weight, plasma corticosterone levels, heart rate, blood pressure, and locomotor activity was studied in both male and female Wistar rats, taking into account the sex differences in stress responsivity. External transfer was found to decrease body weight, increase plasma corticosterone, increase activity, increase heart rate in female rats, but decrease heart rate in male rats. Parameters showed differences between the sexes and light phases. This study shows that acclimatization after transfer is sex-specific and researchers should take the sex into consideration when determining the acclimatization period. It is recommended to allow for acclimatization of at least 8 days in males and two weeks in females after external transfer and timely (2 days before starting experiments) transfer the animals internally to the testing room.

A review of autopsy reports on chimpanzees in or from US laboratories

Approximately 1000 chimpanzees are currently held in five federally owned, or supported, US laboratories. This study reviews 110 autopsy reports on chimpanzees who died from 2001-2011 in laboratories or in sanctuaries (but who were from laboratories), in order to glean information about their premorbid health and causes of death. The findings raise questions about the health status of the chimpanzees remaining in laboratories. Most of the chimpanzees currently held are not involved in active protocols. The Chimpanzee Health Improvement, Maintenance, and Protection (CHIMP) Act 2000 states that chimpanzees "not needed" for research "shall" be accepted into the federal sanctuary system, but criteria for when a chimpanzee is deemed "not needed" are not given. The assessment of "not needed" lies with the Secretary of Health and Human Services, who has left the decision to the discretion of the laboratories. This autopsy review revealed that the majority of the chimpanzees who died in laboratories had been suffering from significant chronic or incurable illnesses, and most often had multi-system diseases that should have made them ineligible for future research, on scientific, as well as ethical, grounds. The study's findings are significant in establishing the need for defined criteria for chimpanzee retirement to sanctuary.

Interpreting Stress Responses during Routine Toxicity Studies

Stress often occurs during toxicity studies. The perception of sensory stimuli as stressful primarily results in catecholamine release and activation of the hypothalamic–pituitary–adrenal (HPA) axis to increase serum glucocorticoid concentrations. Downstream effects of these neuroendocrine signals may include decreased total body weights or body weight gain; food consumption and activity; altered organ weights (e.g., thymus, spleen, adrenal); lymphocyte depletion in thymus and spleen; altered circulating leukocyte counts (e.g., increased neutrophils with decreased lymphocytes and eosinophils); and altered reproductive functions. Typically, only some of these findings occur in a given study. Stress responses should be interpreted as secondary (indirect) rather than primary (direct) test article–related findings. Determining whether effects are the result of stress requires a weight-of-evidence approach. The evaluation and interpretation of routinely collected data (standard in-life, clinical pathology, and anatomic pathology endpoints) are appropriate and generally sufficient to assess whether or not changes are secondary to stress. The impact of possible stress-induced effects on data interpretation can partially be mitigated by toxicity study designs that use appropriate control groups (e.g., cohorts treated with vehicle and subjected to the same procedures as those dosed with test article), housing that minimizes isolation and offers environmental enrichment, and experimental procedures that minimize stress and sampling and analytical bias.

This article is a comprehensive overview of the biological aspects of the stress response, beginning with a Summary (Section 1) and an Introduction (Section 2) that describes the historical and conventional methods used to characterize acute and chronic stress responses. These sections are followed by reviews of the primary systems and parameters that regulate and/or are influenced by stress, with an emphasis on parameters evaluated in toxicity studies: In-life Procedures (Section 3), Nervous System (Section 4), Endocrine System (Section 5), Reproductive System (Section 6), Clinical Pathology (Section 7), and Immune System (Section 8). The paper concludes (Section 9) with a brief discussion on Minimizing Stress-Related Effects (9.1.), and a final section explaining why Parameters routinely measured are appropriate for assessing the role of stress in toxicology studies (9.2.).

Differential effects of maternal immune activation and juvenile stress on anxiety-like behaviour and physiology in adult rats: no evidence for the "double-hit hypothesis"

Environmental disruptions can influence neurodevelopment during pre- and postnatal periods. Given such a large time window of opportunity for insult, the "double-hit hypothesis" proposes that exposure to an environmental challenge may impact development such that an individual becomes vulnerable to developing a psychopathology, which then manifests upon exposure to a second challenge later in life. The present study in male rats utilized the framework of the "double-hit hypothesis" to investigate potential compounding effects of maternal immune activation (MIA) during pregnancy and exposure of offspring to stress during juvenility on physiological and behavioural indications of anxiety in adulthood. We used an established rat model of MIA via maternal treatment with polyinosinic:polycytidylic acid (poly I:C) on gestation day 15 in combination with a model of juvenile stress (applied ages 27-29 d) in offspring to explore potential interacting/additive effects. First, we confirmed our employment of the MIA model by replicating previous findings that prenatal treatment with poly I:C caused deficits in sensorimotor gating in adult offspring, as measured by prepulse inhibition. Juvenile stress, on the other hand, had no effect on prepulse inhibition. In terms of anxiety-related behaviour and physiology, we found that prenatal poly I:C alone or in combination with juvenile stress had no effects on body weight, adrenal weight, and plasma concentration of corticosterone and cytokines in adult rats. MIA and juvenile stress increased anxiety-related behaviour on the elevated plus maze, but did so independently of each other. In all, our findings do not support an interaction between MIA and juvenile stress in terms of producing marked changes related to anxiety-like behaviour in adulthood.

High tail-cuff blood pressure in mice 1 week after shipping: the need for longer acclimation

BACKGROUND

For vendor-derived mice, an acclimation period of 1 week is usually recommended before blood pressure measurements are started. However, we observed hypertension in wild-type vendor-derived mice 1 week after shipping.

METHODS

The index group (n = 12, BALB/c, age 3 months, weight 26-28 g) was shipped overnight (by truck, duration 13 h). Tail-cuff systolic blood pressures (SBPs) of the index group were compared to two control groups (n = 6/group), one acclimated for 3 weeks after shipping, and one derived from an in-house colony.

RESULTS

One week after shipping, SBP in the index group was 141 ± 3 mm Hg. Because this was much higher than reported previously for this strain, acclimation was prolonged. Six weeks after shipping, SBP had fallen to 124 ± 3 mm Hg (P < 0.005). During this time, heart rate also fell from 721 ± 15 to 665 ± 13 bpm (P < 0.01). SBP in the two control groups was also lower than in the index group 1 week after shipping, including the group acclimated for 3 weeks (129 ± 3 vs. 141 ± 3 mm Hg, P < 0.05) and the in-house mice (124 ± 3 vs. 141 ± 3 mm Hg, P < 0.005).

CONCLUSIONS

Vendor-derived mice are hypertensive 1 week after shipping, become normotensive after 3 weeks, but do not return to levels of in-house mice until after 6 weeks. Acclimation periods of at least 3 weeks are required when measuring blood pressure in mice.

A gold standard publication checklist to improve the quality of animal studies, to fully integrate the Three Rs, and to make systematic reviews more feasible

Systematic reviews are generally regarded by professionals in the field of evidence-based medicine as the highest level of medical evidence, and they are already standard practice for clinical studies. However, they are not yet widely used nor undertaken in the field of animal experimentation, even though there is a lot to be gained from the process. Therefore, a gold standard publication checklist (GSPC) for animal studies is presented in this paper. The items on the checklist have been selected on the basis of a literature analysis and the resulting scientific evidence that these factors are decisive in determining the outcome of animal studies. In order to make future systematic reviews and meta-analyses of animal studies possible, to allow others to replicate and build on work previously published, diminish the number of animals needed in animal experimentation (reduction), improve animal welfare (refinement) and, above all, improve the quality of scientific papers on animal experimentation, this publication checklist needs to be used and followed. We have discussed and optimised this GSPC through feedback from interviews with experts in the field of animal experimentation. From these interviews, it became clear that scientists will adopt this GSPC when journals demand it. The GSPC was compared with the current instructions for authors from nine different journals, selected on the basis that they featured a high number of publications on animal studies. In general, the journals' demands for the description of the animal studies are so limited that it is not possible to repeat the studies, let alone carry out a systematic review. By using the GSPC for animal studies, the quality of scientific papers will be improved. The use of the GSPC and the concomitant improvement in the quality of scientific papers will also contribute to decreased variation and increased standardisation and, as a consequence, a reduction in the numbers of animals used and a more reliable outcome of animal studies. It is of major importance that journal editors become convinced of and adopt these recommendations, because only then will scientists follow these guidelines to the full extent.

Adolescent development of neuron structure in dentate gyrus granule cells of male Syrian hamsters

Hippocampal function, including spatial cognition and stress responses, matures during adolescence. In addition, hippocampal neuron structure is modified by gonadal steroid hormones, which increase dramatically at this time. This study investigated pubertal changes in dendritic complexity of dentate gyrus neurons. Dendrites, spines, and cell bodies of Golgi-impregnated neurons from the granule cell layer were traced in pre-, mid-, and late-pubertal male Syrian hamsters (21, 35, and 49 days of age). Sholl analysis determined the number of intersections and total dendritic length contained in concentric spheres set at 25-microm increments from the soma. Spine densities were quantified separately in proximal and distal segments of a subset of neurons used for the Sholl analysis. We found that the structure of neurons in the lower, but not upper, blade of the dentate gyrus changed during adolescence. The lower, infrapyramidal blade showed pruning of dendrites close to the cell body and increases in distal dendritic spine densities across adolescence. These data demonstrate that dentate gyrus neurons undergo substantial structural remodeling during adolescence and that patterns of maturation are region specific. Furthermore, these changes in dendrite structure, which alter the electrophysiological properties of granule cells, are likely related to the adolescent development of hippocampal-dependent cognitive functions such as learning and memory, as well as hippocampus-mediated stress responsivity.

The use of radiotelemetry to assess the time needed to acclimatize guineapigs following several hours of ground transport

The objective of this study was to investigate the effect of ground transportation on guineapigs. Physiological parameters, i.e. heart rate (HR), body temperature (BT) and activity (ACT), were measured before and after transport, using previously implanted radiotelemetry transmitters. Body weight was measured before and after transport. After a postsurgical recovery period and data recording at the breeder's facility, the animals were transported for 2.25 h (Group 1) and for 7.5 h (Group 2) to a different animal facility. Data collection started immediately after arrival at the second animal facility. All parameters measured changed significantly after transport. These results suggest that a 10- to 12-day period is required for guineapigs to return to pre-transport levels of HR, BT and ACT.

To breed or not to breed? Empirical evaluation of drug effects in adolescent rats

The recent upsurge of research on adolescent rats raises the issue of the extent to which different methods of rodent procurement might affect results. Here, we examined the effects of acute and repeated dosing with two antipsychotics, haloperidol and clozapine, and Delta(9)-tetrahydrocannabinol [Experiments 1 and 2, respectively] in adolescent rats of both sexes that differed in shipping status (i.e., shipped from a commercial breeder at weaning or bred in-house). In each experiment, test drugs produced effects that were characteristic for their respective classes in previous studies with adult rodents. Both haloperidol and clozapine produced catalepsy and haloperidol decreased locomotion in shipped and bred rats of both sexes, with sensitization to haloperidol-induced catalepsy developing with repeated dosing. The most prominent between-status difference in this experiment was greater sensitivity of the shipped rats to haloperidol-induced changes in locomotor activity over a wider dose range, an effect that was especially evident in females. In Experiment 2, vehicle levels of motor activity were decreased in bred rats (which did not occur in Experiment 1), resulting in flattening of the Delta(9)-tetrahydrocannabinol dose-effect curve for this measure in bred rats of each sex. Acutely, Delta(9)-tetrahydrocannabinol produced antinociception, hypothermia and catalepsy in both groups of rats, with tolerance developing after repeated dosing. Status-related differences were sex-dependent. Whereas bred female rats were more sensitive to Delta(9)-tetrahydrocannabinol's antinociceptive effects, shipped male rats were more sensitive to its antinociceptive effects as well as to its hypothermic and cataleptic effects. Together, the results of these descriptive experiments suggest that between-status differences tend to be quantitative rather than qualitative. Further, these results suggest that careful attention to issues related to rodent procurement during adolescence is warranted and may help to account for divergent findings in different labs.