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Intraperitoneal (IP) injection is a common route of anesthetic administration in mice. Ketamine-xylazine (KX) anesthesia is one of the most widely used IP protocols, but has limitations. Etomidate is an alternative to ketamine that has been used in both human and veterinary medicine yet has not been widely studied in mice. The purpose of this study was to evaluate etomidate-xylazine (EX) anesthesia as an alternative to KX. We hypothesized that EX would be as safe and effective as KX, with both sex- and strain-dependent differences. Male and female Crl:CD1(ICR), C57BL/6NCrl, BALB/cJ and NU/J mice were given a single IP dose of ketamine 100 mg/kg and xylazine 10 mg/kg or etomidate 20 mg/kg and xylazine 10 mg/kg. Sedation times were similar between KX and EX, with CD1 mice exhibiting shorter sedation times. Surgical anesthesia was achieved in 44% of EX mice, compared with 4% of KX mice. C57BL/6NCrl mice were significantly more likely to achieve surgical anesthesia when given EX (94%) or KX (18%) than were other strains. In all strains except C57BL/6NCrl mice, females were more likely to reach surgical anesthesia than males. Several mice experienced an adverse hyperexcitement response during induction, with BALB/cJ (79%) and NU/J (87%) mice given EX significantly more likely than other strains to experience hyperexcitement. EX and KX protocols had no overall differences in lowest respiration rate, lowest systolic blood pressure, lowest rectal temperature, or levels of acidosis, although the lowest heart rates were significantly higher with EX, indicating that EX and KX have similar safety profiles. Thus, EX and KX administration were associated with several significant physiologic differences when comparing sexes or individual strains. Our results indicate that EX is an equally effective sedative and a more effective surgical anesthetic than KX; however, EX is only recommended for invasive procedures in C57BL/6 mice due to the high rate of hyper-excitement and inconsistent surgical depth seen in other strains. Further study is needed to optimize EX for use in multiple mouse strains.

Institutional health and safety programs are responsible for minimizing personnel risk in working with animals that have been administered hazardous chemicals. Regulations and associated guidance a...

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.

Obesity results from a number of factors including socio-environmental influences and rodent models show that several different stressors increase the preference for calorically dense foods leading to an obese phenotype. We present here a non-human primate model using socially housed adult female macaques living in long-term stable groups given access to diets of different caloric density. Consumption of a low fat (LFD; 15% of calories from fat) and a high fat diet (HFD; 45% of calories from fat) was quantified by means of a custom-built, automated feeder that dispensed a pellet of food when activated by a radiofrequency chip implanted subcutaneously in the animal's wrist. Socially subordinate females showed indices of chronic psychological stress having reduced glucocorticoid negative feedback and higher frequencies of anxiety-like behavior. Twenty-four hour intakes of both the LFD and HFD were significantly greater in subordinates than dominates, an effect that persisted whether standard monkey chow (13% of calories from fat) was present or absent. Furthermore, although dominants restricted their food intake to daylight, subordinates continued to feed at night. Total caloric intake was significantly correlated with body weight change. Collectively, these results show that food intake can be reliably quantified in non-human primates living in complex social environments and suggest that socially subordinate females consume more calories, suggesting this ethologically relevant model may help understand how psychosocial stress changes food preferences and consumption leading to obesity.

Euthanasia by anesthetic agents is commonly performed prior to tissue collection in order to minimize pain and distress to the animal. However, depending on their mechanism of action as well as administration regimen, different methods of anesthesia may trigger an acute stress response through engaging the hypothalamic-pituitary-adrenal (HPA) axis, which can impact numerous other physiological processes that the researcher may wish to examine as endpoints. We investigated the effects of the commonly used anesthetic agent isoflurane on two different endpoints related to the stress response: plasma corticosterone levels and gene expression of the glucocorticoid receptor (GR) as well as several of its regulators including FK506-binding protein 51 (Fkbp5) in the hippocampus of male and female rats. Our results indicate that brief exposure to anesthesia by isoflurane prior to decapitation can alter plasma corticosterone levels differentially in male and female rats within minutes without impacting gene expression in the hippocampus. We conclude that collection methods can influence stress-related physiological endpoints in female rats and the potential influence of even brief anesthesia as well as sex differences in response to anesthesia should be evaluated during the experimental design process and data interpretation. This finding is particularly important in light of new NIH standards regarding sex and reproducibility, and care should be taken to be certain that sex differences in endpoints of interest are not an artifact of sex differences in response to collection paradigms.

Laboratory animals, including birds, play an important role in biomedical research. The humane care and management of these animals is an ongoing concern. A new addition to the acclaimed Laboratory Animal Pocket Reference series, The Laboratory Bird is the first publication dedicated to the care and use of avian species in the research setting.Cove

Publisher Summary The guinea pig, like many animals used in biomedical research today, first became popular to enthusiasts and fanciers. This popularity fostered familiarity with its behavior, physiology, and suitable husbandry conditions, and this knowledge about care and husbandry subsequently allowed successful transition into laboratory housing, making it a popular research model. The guinea pig first served as a useful animal model of disease and was used in the study of respiratory physiology. Guinea pigs were further used in studies of infectious disease, and seminal work on the role of certain vitamins in maintaining health. Through time it was learned that, beyond the virtues of its relatively small size and docile nature, the guinea pig possesses anatomical and physiological features that make it uniquely suited to certain studies. For example, guinea pigs are useful in reproductive studies because they and humans share similarities in placental structure, their gestation period of 68 days can be divided effectively into trimesters akin to the human condition, and they can develop pregnancy toxemia. The most commonly used variety is the Hartley albino stock, but the inbred strains 2 and 13, and euthymic hairless stock are also used with some frequency. A principal reason for the overall decline in use is the increased use of mice as a favored animal model. The paucity of inbred guinea pig strains and the limited number of specific reagents for use with the species are two factors that generally limit the use of this species in research in the foreseeable future.

Moxidectin has been used safely as an antiparasitic in many animal species, including for the eradication of the mouse fur mite, Mycoptes musculinus. Although no side effects of moxidectin have previously been reported to occur in mice, 2 strains of the senescence-accelerated mouse (SAMP8 and SAMR1) sustained considerable mortality after routine prophylactic treatment. To investigate the mechanism underlying this effect, moxidectin toxicosis in these mice was evaluated in a controlled study. Moxidectin was applied topically (0.015 mg), and drug concentrations in both brain and serum were analyzed by using HPLC coupled with mass spectrometry. The moxidectin concentration in brain of SAMP8 mice was 18 times that in controls, and that in brain of SAMR1 mice was 14 times higher than in controls, whereas serum moxidectin concentrations did not differ significantly among the 3 strains. Because deficiency of the blood–brain barrier protein P-glycoprotein leads to sensitivity to this class of drugs in other SAM mice, Pgp immunohistochemistry of brain sections from a subset of mice was performed to determine whether this commercially available analysis could predict sensitivity to this class of drug. The staining analysis showed no difference among the strains of mice, indicating that this test does not correlate with sensitivity. In addition, no gross or histologic evidence of organ toxicity was found in brain, liver, lung, or kidney. This report shows that topically applied moxidectin at a standard dose accumulates in the CNS causing toxicosis in both SAMP8 and SAMR1 mice.