The Association of Primate Veterinarians (APV) and the American Society of Primatologists (ASP) acknowledge the significant benefits of environmental enrichment to the welfare of nonhuman primates (NHP) housed in zoos, sanctuaries, research settings, and other captive environments. Environmental enrichment introduces novelty, increases environmental complexity, and encourages the expression of species-typical behaviors. Every effort should be made to provide captive NHP with an enriched, functionally appropriate environment that promotes successful coping, increases welfare, and supports more translatable animal models. APV and ASP collectively strongly endorse the use of multimodal environmental enrichment as an integral component of captive NHP care andPurpose
Streptobacillus moniliformis is a Gram-negative bacterium and the causative agent of rat bite fever. In 2020, members of a laboratory-born thirteen-lined ground squirrel (Ictidomys tridecemlineatus) colony tested positive for S. moniliformis during routine pathogen screening at the University of Wisconsin–La Crosse. These animals were asymptomatic and continued to be monitored and tested until treatment was attempted with tetracycline in May 2023. Two different treatment regimens were attempted. Squirrels treated with 10-mg treats twice daily for 7 to 10 d were no longer positive for S. moniliformis. New squirrels entering the University of Wisconsin–La Crosse animal facility were tested. The only additional positive case was in a wild-caught thirteen-lined ground squirrel in 2024. This squirrel subsequently tested negative following the same tetracycline treatment. Based on the identification of this zoonotic agent in both laboratory and wild-caught species, we recommend regular screening for S. moniliformis in captive squirrels and prudent management decisions when handling these animals and their waste. To our knowledge, this is the first published report of confirmed S. moniliformis in squirrels.
Common marmosets (Callithrix jacchus) are increasingly used in biomedical research and often undergo surgery as part of IACUC-approved protocols. Therefore, pain control is essential to their clinical management and welfare. Extended-release buprenorphine is a valuable opioid analgesic option, as it can maintain plasma concentrations above therapeutic levels (0.1 ng/mL) for at least 72 h. However, no validated model is available to verify the analgesic effect of buprenorphine in marmosets. Therefore, this study compared the effects of buprenorphine-ER-LAB (Bup-ER-LAB) at 0.15 mg/kg and Ethiqa XR (EXR) at 0.15 and 0.1 mg/kg administered subcutaneously in marmosets undergoing surgical oocyte collection (n = 12 females) or vasectomy (n = 9 males). We hypothesized that these doses and formulations would provide similar analgesia during the 72-h postoperative period, determined with a marmoset composite measure pain scale designed for cage-side semiquantitative assessment of postoperative pain. The composite measure pain scale focused on animal appearance, activity, body posture/integument, respiration, surgical site, and social interactions, each with different subcategories and corresponding points to obtain a cumulative score. Animals were also assessed cage-side for locomotor activity and injection site reactions. No to minimal pain was scored, and no marmoset needed rescue analgesia. In total, 56% of the males and 25% of the females showed increased activity, which could last up to 48 h. Increased activity occurred in 57% of the BUP-ER-LAB group, 43% of the EXR 0.15 mg/kg group, and 14% of the EXR 0.1 mg/kg group (3 males and 4 females per group). Injection site reactions (erythema and/or swelling) occurred in 57% of the Bup-ER-LAB group, 29% of the EXR 0.15 mg/kg group, and 14% of the EXR 0.1 mg/kg group. Based on our results, we conclude that these formulations provide similar postoperative analgesia in marmosets, and an EXR dosage between 0.1 to 0.15 mg/kg provides adequate analgesia with less increase in activity and risk for injection site reaction.
Multimodal analgesia provides superior pain control compared with single-agent analgesic approaches. However, certain analgesic drug classes such as NSAIDs and opioids may be contraindicated in some studies due to their mechanisms of action, highlighting the need for alternative analgesic options. Little information is available as to the efficacy of alternative supplementary analgesics in laboratory rodents. Here, we investigate the impact of ketamine as an adjunctive analgesic postlaparotomy in 32 female Sprague–Dawley (SD) rats. Rats received either 4 mg/kg Meloxicam in Extended-Release Polymer (Melox-ER) or 1 mg/kg Buprenorphine Base in Extended-Release Polymer (Bup-ER), along with either ketamine (30 mg/kg SC) or volume-matched saline (n = 8 per treatment group). Postoperative pain behaviors were assessed via video scoring at 30, 90, and 150 min postoperatively, and cage-side evaluations were performed in-person at 3, 6, 12, 24, 32, 48, 56, and 72 h postoperatively. Rat grooming behavior, assessed by the grooming of fluorescent oil from the nape, was evaluated as an indirect method of assessing analgesic efficacy. All rats that received ketamine exhibited higher activity levels, reduced incisional licking, and fewer pain-associated behaviors than nonketamine-treated rats during the initial 90-min postoperative period. Rats that received Melox-ER demonstrated fewer pain-associated behaviors than Bup-ER-treated rats in the acute postsurgical period, regardless of ketamine treatment. Rats treated with Bup-ER took significantly longer to groom fluorescent oil from their fur compared with Melox-ER-treated rats. Our study demonstrates that ketamine confers significant analgesic effects for at least 90 min postoperatively and supports the use of fluorescent oil grooming transfer scores as a method for evaluating postoperative analgesia.
Socially housing gregarious species enhances animal welfare by increasing affiliative interactions, exploratory behaviors, and other species-specific behaviors, while conferring decreased rates of abnormal behaviors. In addition, most regulatory guidelines promote social housing as a minimum standard to promote the wellbeing of the animals used in research. However, research performed to better understand the process of performing and evaluating social housing, particularly in research pigs, is severely lacking. Social housing does not come without risks, namely wounding during introductions. In this study, we aimed to assess predictors of agonistic and affiliative interactions between newly paired swine and to evaluate the use of a simple wound scoring system as a metric of the introduction process. We assessed whether the pigs’ relative weight difference or prior social experience influenced the behavior between pigs during the initial introduction and their longer-term compatibility as measured 72 h later. To further assess how stressful the pairing process was, we measured the pigs’ heart rate during social introductions. We accomplished this by recording data from 50 pairing events of female Yorkshire pigs. While agonistic behavior was observed in two-thirds of the pairing events, rates of agonistic behavior fell significantly by 72 h after pairing. In contrast, affiliative behavior was observed in more than three-fourths of the pairs at the initial introduction and rates remained equally high 72 h later. We found no correlation between the pigs’ weight difference and the rates of agonistic behavior observed, although prior pairing experience did mediate the rate of agonistic behavior observed such that previously paired pigs exhibited more agonistic behavior than did socially naive individuals. In addition, we validated the use of wound score as a proxy for more detailed observations of wounding behavior. Overall, we recommend socially housing female research pigs and allowing them to naturally sort out social rankings through interaction.
Previous articles republished as part of the From the Archives series documented historical considerations of laboratory rodent housing options such as proper diet and bedding as well as practical cage construction. Plastic shoebox-style cages in various sizes were being used in the 1950s, but these were provided in an open-top configuration. The specific-pathogen-free rat colony described in the last installment was managed using exclusion methods focused on maintaining a barrier at the room level. However, it was soon recognized that, in both academic and commercial colonies, there were situations that would benefit greatly from a system thatCommentary
Telemetry is a widely used method for obtaining physiologic data from rats, but it is uncertain how distressing it is for the animals to live with an implanted transmitter for long periods. The present study aimed to assess this impact by analyzing 2 stress-sensitive biomarkers excreted in feces. Male Brown Norway (BN; n = 12) and Fisher 344 (F344; n = 12) rats were housed for 8 wk in IVCs and then for 8 wk in open top cages, in groups of 3, with one rat in each group carrying a transmitter. At 2-wk intervals, the rats were housed singly for 6 h (0600 to 1200), and voided fecal pellets were collected and frozen. Fecal glucocorticoids and fecal IgA from each rat were quantified and data subsequently analyzed using a repeated-measures mixed-model ANOVA. Both rat strain and transmitter carriage were found to significantly influence fecal corticosterone excretion. Overall, F344 rats excreted higher amounts of feces as compared with BN rats. In F344 rats with a transmitter the corticosterone values were 21% and in BN rats 47% higher than in controls, on average. Neither the rat strain nor an implanted transmitter seemed to have an impact on the amounts of fecal IgA excreted, but excretion increased significantly with age. In conclusion, in both rat strains, there was an increase in corticosterone excretion attributable to transmitter carriage, indicative of mild to moderate stress.
Reduced xenograft engraftment and delayed tumor growth in immunocompromised mice have been associated with infection by Corynebacterium bovis, a highly contagious bacterium that causes sporadic clinical disease and chronic shedding. To learn what effect C. bovis infection may have on the reproducibility of preclinical cancer studies, subcutaneous tumors were monitored in male and female nude (Foxn1nu) mice topically infected with C. bovis 2 to 3 weeks prior to cell injection (chronically infected) or at the time of cell injection (acutely infected) and compared with tumors in uninfected control mice. There were largely no significant differences in tumor engraftment rates, final tumor weights, or final tumor volumes between infection groups for any of the 3 established human cell lines; that is, SJSA-1, an osteosarcoma; HT-29, a colorectal adenocarcinoma; and A549, a lung carcinoma. However, HT-29–engrafted tumors grew significantly more slowly in acutely infected males than in the chronically infected or uninfected males, although no difference was present between the HT-29–engrafted female groups. No epidermal hyperplasia or hyperkeratosis was present in either of the infected groups, compared with the controls, which paralleled the absence of scaly skin clinically across all groups. In summary, our results suggest that C. bovis as a single pathogenic agent may have a limited effect on xenograft engraftment and growth. Investigators using different strains of immunocompromised mice, different cell lines, or mice housed in facilities with different health status from that described in the present study but endemic for C. bovis should perform pilot studies to determine whether tumor engraftment and/or growth is affected by infection.
Rats regularly undergo surgical procedures that may result in pain. Alleviation of unnecessary pain is an ethical and regulatory responsibility. Buprenorphine is an opioid analgesic commonly used in rats and requires dosing every 6 to 8 h to be effective. Frequent administration is time consuming and may increase stress, post-surgical pain, and dehiscence in rats, making the use of long-acting formulations an attractive alternative. A transdermal buprenorphine solution (TBS), FDA approved for use in felines, is commercially available and effective for up to 96 h. We hypothesize that a single dose of TBS in rats will result in clinically relevant plasma buprenorphine concentrations (greater than 1 ng/mL) for up to 96 h. To test this, 39 rats were randomly assigned to the following treatment groups: low dose (LD; 5 mg/kg; n = 6 females, 6 males), high dose (HD; 10 mg/kg; n = 6 females, 6 males), and vehicle control (CON; n = 7 females, 8 males). TBS or anhydrous ethanol (CON) were topically applied. Blood was collected at 4, 24, 72, 96, and 168 h postadministration, and buprenorphine concentrations were determined via HPLC-MS. To quantitatively assess adverse effects, daily fecal output, food intake, and body weight were measured, and observations of hematuria and skin lesions were documented. Plasma buprenorphine concentrations exceeded 1 ng/mL in all TBS rats at 4, 24, 48, and 72 h. No rats experienced serious adverse effects or developed gross lesions at the application site. The HD group had decreased fecal output compared with CON. Both TBS groups had reduced weight gain compared with CON. These results suggest that TBS dosed at 5 to 10 mg/kg could provide analgesia for up to 3 d in rats, and administering a lower dose mitigates some adverse effects.
The administration of antibiotics is a critical variable when developing animal models of infection. Handling and needle use, however, can cause distress in the animals, leading not only to irritability of the animal but potentially skewed inflammatory data in studies that closely measure this response. Cefadroxil, a cephalosporin with excellent intestinal absorption, can be administered enterally. Oral gavage and drinking water dosing, 2 common methods of oral administration, each have their own disadvantages, including distress as a result of handling and potential death from accidental drug administration into the lungs; and incomplete consumption, respectively. Here, we developed and evaluated a method for precise voluntary oral consumption of cefadroxil for use in a rodent model of musculoskeletal infection. Sprague-–Dawley rats were trained to voluntarily consume a wafer or puree containing 1 of 2 doses of cefadroxil. Blood plasma was collected to measure systemic concentrations of antibiotics 30, 60, and 120 min following consumption. Finally, the voluntary consumption method was used in a rat model of musculoskeletal infection to evaluate efficacy. Following a 5-d training regimen, the number of animals that consistently ate the drug increased from 2/10 to 10/10 and the time to consume decreased from 16 min to 6 min. The highest cefadroxil dose, 23.2 mg/kg, reached a peak plasma concentration of 4.8 μg/mL, 1 h after consumption when the puree was used compared with 2.9 μg/mL, 2 h after wafer consumption. When used in a rat model of musculoskeletal infection, the rats continued to voluntarily consume the drug, and consumption of cefadroxil by puree reduced the bacteria bioburden in the bone tissue compared with the nontreated control. Our results show that precise voluntary consumption is a viable method to administer drugs to rats.
Avian anesthesia in translational medicine must account for various species, yet there is limited research specifically on turkeys used in scientific studies. Premedication is commonly used in veterinary medicine to produce smoother anesthetic events for patients and staff. This study assessed premedication of turkeys using intramuscular midazolam (MDZ) or midazolam/butorphanol (MDZ-B) compared with saline control to improve handling/patient behaviors. Female turkeys (n = 35) undergoing a surgical procedure for an orthopedic study were randomly divided into 3 groups (midazolam: 2 mg/kg IM; midazolam: 2 mg/kg IM and butorphanol: 1 mg/kg IM; or saline control: 0.45 mL/kg). Blinded raters qualitatively scored perianesthetic criteria at approximately 10 min post premedication (body position, restraint required, and muscle relaxation), following induction (intubation attempts/ease and apnea), and at recovery (restraint required, tremors, and wing flapping). Relevant time points tracked quantitative data including time of premedication, induction, intubation, inhalant anesthesia end time, and recovery. Premedication with either MDZ or MDZ-B improved perianesthetic parameters such as achieving sternal recumbency, lessening the restraint required, and improving muscle relaxation when compared with saline control. Use of MDZ or MDZ-B significantly decreased the time from premedication to intubation compared with control. The saline control group had significantly faster recoveries than the premedication groups. Choosing an appropriate anesthetic premedication protocol involves considering many factors. Turkeys premedicated with either MDZ or MDZ-B had easier induction leading to improved animal handling and restraint by staff. Due to significantly longer recovery times, MDZ or MDZ-B may increase the periprocedural labor required yet offer a smoother, less traumatic recovery.
Oral gavage (OG) dosing can be stressful to pigs and is associated with the risk of complications. To evaluate a potential refinement, we compared the pharmacokinetics of a drug with a known aversive taste (metronidazole) administered orally to 6 Gottingen minipigs with voluntary cooperation of the animal (voluntary oral [VO]) to 6 Gottingen minipigs dosed by OG. Blood was collected predose and at 0.5, 1, 2, 4, 8, and 24 h postdose and analyzed for drug concentration. Pharmacokinetic parameters for metronidazole were calculated, including Cmax, Tmax, AUC (from 0 to 24 h), and the ratios of AUC and Cmax between 2 dosing methods (AUC OG/VO ratio and Cmax OG/VO ratio, respectively). The time required to dose (dosing interval) and animal and staff acceptance of the dosing procedures were also assessed. All animals were dosed successfully, but one animal in each group was noted to have dosing difficulty. Mean dosing interval for OG dosing was greater than for VO (2.6 ± 0.24 min SD compared with 1.6 ± 0.36 min, respectively). VO dosing required fewer handlers, appeared to be less stressful to the animals, and was reported to be more ergonomically favorable than OG dosing. There were no significant differences in exposure including Cmax, Tmax, and AUC between OG and VO dosing. The OG/VO ratio was 1.27 for AUC and 1.25 for Cmax. Both animals with difficulty during dosing had pharmacokinetically inconsistent concentration–time profiles when compared with all other animals. These apparent differences were within the expected variability seen in pharmacokinetic studies. VO dosing may be a potential refinement for a single-dose pharmacokinetic study of an aversive tasting test material to minipigs.
Regular monitoring of laboratory zebrafish health status is crucial for ensuring both animal welfare and scientific validity in aquatic research. While zebrafish usage in research has increased substantially due to their biological advantages and experimental benefits, including high fecundity and vertebrate similarity, systematic health monitoring remains uncommon in South Korean facilities. This study presents a comprehensive assessment of zebrafish colony health monitoring practices in South Korea, combining comparative survey data from 2018 and 2024 with microbiologic and environmental analyses of 11 facilities. Our survey revealed a trend: despite facility scale expansion (proportion of the large-scale facilities with >200 tanks increasing from 41.7% to 54.5%) and universal adoption of recirculation systems, monitoring efforts have declined. The percentage of facilities without active monitoring increased from 50.0% in 2018% to 81.8% in 2024, while awareness of monitoring necessity decreased from 91.7% to 72.7%. To investigate these issues, we conducted analyses across 11 facilities (6 research institutes and 5 local suppliers). The analysis encompassed multiple parameters: 1) detection of key infectious agents (Mycobacterium spp., Aeromonas hydrophila, Flavobacterium columnare, Pseudocapillaria tomentosa, Pseudoloma neurophilia, Pseudomonas aeruginosa) in sump tank biofilm, zebrafish specimens, and feed samples; and 2) evaluation of water chemistry parameters (pH, nitrate concentration, conductivity) in tank water. Our findings revealed that Mycobacterium spp. were present in biofilm samples from all facilities and in >80% of fish samples from research facilities. Aeromonas hydrophila was detected across all sample types. Both Mycobacterium spp. and A. hydrophila are opportunistic pathogens that necessitate careful consideration in long-term zebrafish experiments. Furthermore, evaluation of water quality analyses indicated widespread deviations from acceptable parameters, particularly in nitrate levels and pH values. Our results underscore the need for implementing standardized monitoring protocols and enhanced water system management to safeguard research integrity, animal health, and occupational safety in zebrafish facilities.
Accurate postoperative pain management is crucial for good animal welfare and science. We sought to evaluate mouse postoperative pain management efficacy by measuring activity using a novel triaxial acceleration device—the Rodent Fitbit-like telemetry device (RFB)—to monitor home cage activity. To determine if analgesics impacted activity levels, we evaluated activity in C57BL/6 male and female mice (n = 6) that were attached with the RFB and administered EthiqaXR (XR; 3.25 mg/kg), meloxicam sustained release (MSR; 6 mg/kg), combined XR/MSR, or bupivacaine (5 mg/mL) compared with control mice provided sterile saline (5 mL/kg) subcutaneously. Activity in XR/MSR and XR-treated mice was significantly increased on night 0 (N0) but only trended downward from N2 to N4 compared with baseline. No significant changes in activity were detected after administration of MSR, bupivacaine, and saline. We examined the effective analgesic period of XR, MSR, XR/MSR, and bupivacaine based on electric von Frey and the RFB using a hind paw incision pain model in C57BL/6 male (n = 8) and female mice (n = 7) attached with the RFB. Preoperative XR and XR/MSR mice had reduced pain based on von Frey with no reduction in activity based on the RFB compared with other treatment groups. Only mice provided saline demonstrated a significant decrease in activity on N0, suggesting limited duration of spontaneous pain elicited from the minor pain model. In summary, activity was an effective and sensitive indicator for detecting pain using a paw incision pain model in C57BL/6 mice within the first 24 h postsurgery. Additional studies using a major operative procedure should be performed to determine the effectiveness of activity as a pain detection indicator.
The use of hydrochloric acid treatment of drinking water in many academic research rodent colonies and commercial vendors prompted us to investigate its effect on tooth enamel health in mice. Drinks with a low pH such as fruit juices and soft drinks have been demonstrated to cause demineralization of tooth enamel in humans and rodents. This study explored the hypothesis that acidified drinking water at the recommended range of 2.5 to 3.0 pH can lead to enamel erosion and compromised tooth integrity in mice. Specifically, we sought to quantify the effects of pH 2.5 or 3.0 daily drinking water exposure on molar enamel and bone mineral density over 1 and 3 mo. Methylene blue was used to quantify enamel erosion of the molar teeth, while dual-energy X-ray absorptiometry was used to quantify the bone mineral density of the mandible. After 1 mo of drinking water exposure, no statistically significant difference between the groups in enamel erosion or bone mineral density was observed. However, after 3 mo, a significant difference in enamel erosion for the pH 2.5 group compared with the other groups was identified, suggesting a potentially destructive process. There were no differences in bone mineral density between groups at any time point. These findings indicate that acidified drinking water of pH 2.5 may have deleterious effects on the enamel integrity of molar teeth in mice; however, drinking water of pH 3.0 seems safe for tooth enamel in mice during a short-term exposure of 3 mo. As this study only had a 1- to 3-mo exposure period, further study is needed to determine the effects of longer-term use of acidified drinking water at pH 3.0 in mice.
Intraperitoneal injections are commonly used for systemic drug administration in various laboratory animals, including rodents and zebrafish (Danio rerio). Although these fish have rapidly gained popularity in biomedical research, the accuracy of intraperitoneal drug delivery (due to potential leakage from the injection site) has not been previously evaluated in zebrafish. To investigate this issue, we injected adult zebrafish with 10 µL/g of a dye (1% Evans Blue) intraperitoneally and estimated dye leakage by measuring the optical density of water where the fish were kept for 20 min past injection. Overall, we found that intraperitoneal injections resulted in an estimated approximately 10% immediate leakage and approximately 0.01% secondary leakage (of the injected dye volume), confirming the relative accuracy of intraperitoneal injection as a reliable drug delivery method in adult zebrafish.
Rodent health monitoring (HM) programs are designed to detect infectious agents in rodents that have the potential to negatively impact animal health or research findings. These programs are an essential component for verifying the desired health status of a research mouse colony. While multiple factors can provide information about a colony’s health status, including clinical observations, gross and microscopic pathologies, unexpected experimental results, and other factors, the term ‘health monitoring program’ in this review refers specifically to the routine screening/testing of laboratory mice or their environment for the presence (for example, by bacterial culture or visual identification or ectoparasites)Introduction
Behavioral tests in laboratory animals, particularly rodents, are considered vital for understanding the mechanisms underlying depression and evaluating potential treatments. However, ethical concerns regarding the use of traditional methods, such as the tail suspension test and the forced swimming test, which induce significant distress, have led to calls for more humane alternatives. In this paper we explore the ethical considerations surrounding common behavioral tests used in depression research, focusing on the tail suspension test’s and forced swimming test’s potential to cause harm to animals and their controversial relevance to human depression. Alternative methods, including the nest building behavior assessment and social interaction observations, provide valuable insights into depression-like behaviors without inducing unnecessary stress. We advocate for a shift toward mild-stress testing methods aligned with the 3Rs principle (replacement, reduction, and refinement). By integrating these humane practices, and promoting education on alternative methods, the scientific community can enhance the ethical integrity and translational relevance of preclinical depression research.
Grapiprant belongs to the newer piprant class of nonsteroidal anti-inflammatory drugs (NSAIDs) and is FDA approved for treatment of osteoarthritis in dogs. The compounds act as an antagonist at the prostaglandin E2 EP4 receptor and is therefore also noncyclooxygenase inhibiting. This mechanism of action reduces the potential for adverse side effects associated with cyclooxygenase inhibition and makes it a promising drug for long-term use in nonhuman primates (NHPs) with chronic inflammatory conditions. In this study, we sought to establish pharmacokinetic parameters of an oral oil suspension of grapiprant in healthy, fasted male and female rhesus macaques (Macaca mulatta) with a single oral dose of 2 mg/kg, the current FDA-approved dose in dogs. Blood was collected at time 0 (baseline) and at 9 additional time points (0.25, 0.5, 1, 2, 4, 8, 12, 24, and 48 h) after dosing. Grapiprant plasma concentration was quantified using liquid chromatography–tandem mass spectrometry. Our data show that rhesus macaques absorb grapiprant more slowly (Tmax = 2 h for all subjects) and at a lower level (Cmax = 23.8 ± 19.6 ng/mL, AUClast = 77.5 ± 42.9 ng·h/mL) than published values in dogs. No significant difference was noted in pharmacokinetic parameters between males and females; however, females showed more variability in pharmacokinetic parameters than did males. Significant age effects were not observed, although a positive correlation between Cmax and AUClast with age in males was noted. Our data suggest that higher doses should be explored in rhesus macaques, with a need for further investigation into the pharmacodynamics of grapiprant to establish an efficacious therapeutic dose in this species and other NHPs.
While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechani- cal pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague–Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.Abstract
The Whitten effect is a widely used tool for manipulating the mouse estrous cycle and generating reproductively active females within the laboratory setting. Typically, peak numbers of sexually receptive mice occur following exposure to male pheromones, resulting in a higher number of successful copulations on the third day after exposure. Although this method has improved efficiencies, the percentage of females mated and subsequently deemed to be pregnant/pseudopregnant remains relatively low, around 50%. In experiment 1, we aimed to 1) further understand cyclicity; 2) determine whether the initial cycle stage plays an importance on day 3 receptivity; and 3) identify any repetitive patterns/cycle stabilization. Mice (n = 27) were assigned to group cages according to cycle stage (proestrus, estrus, metestrus, diestrus). Experiment 2 was developed to determine an optimum treatment to promote receptivity by exposure to various pheromone stimuli. Mice (n = 45) were randomly assigned to 5 treatment groups (PBS-treated sham soiled bedding, male soiled bedding, live male, pregnant females, and lactating females). In both experiments, daily vaginal cytology was performed for 21 days to determine the cycle stage. Results from experiment 1 indicate that the initial cycle stage did not contribute to day 3 receptivity, although synchronization within several groups/cages was noted, and that the greatest numbers of estrous animals were obtained on days 6 and 7. Experiment 2 revealed that exposure to live males and lactating females both significantly improved receptivity compared with the PBS, male soiled bedding, and pregnant female groups. These results indicate that current strategies used for routine synchronization could be further improved through alternative housing regimens without compromising animal welfare.Abstract