Investigating the Effect of Enterally Administered Capromorelin on Body Weight in Mice (Mus musculus).

Significant weight loss in mice (Mus musculus) is a welfare concern and can alter physiology and behavior in ways that may confound research aims. In this study, factorial design was used to investigate the effect of enterally administered capromorelin on changes in mouse body weight overall and with various research-related interventions, such as administration of analgesics, anesthesia, or surgery. BALB/c mice (n = 61 [27 males/34 females] for analysis) were randomized into 8 intervention-treatment groups with 2 treatment allocations: capromorelin (10 mg/kg) or control, and 4 intervention allocations: no intervention; buprenorphine extended-release (XR) alone; buprenorphine XR, meloxicam, and anesthesia; or surgery under anesthesia with buprenorphine XR, meloxicam, and bupivacaine administered. Mice were habituated to handling, weighing, and voluntary consumption of condensed milk, which was used as the control solution and later a vehicle for capromorelin delivery, for 5 d (days 0 to 4). Then, mice received their interventions followed by 3 days of daily treatment or control administration (days 7 to 9). Body weights were measured daily (days 8 to 11 and day 14) to compare with baseline weights (days 0 to 4 and day 7) and evaluate for treatment and intervention effects on body weight. The interventions resulted in a decrease in group body weights 3 and 4 d after the interventions were conducted. Overall, body weights increased more in mice given capromorelin compared with control, and mice treated with capromorelin returned to, or exceeded, baseline weights faster. The weight loss was mitigated by capromorelin administration in all interventions except for the buprenorphine XR-only group. It is recommended to clinically consider enterally administered capromorelin to mitigate research-induced weight loss in mice.

Comparison of Two Hair Removal Methods in Sprague-Dawley Rats (Rattus norvegicus).

Rats commonly undergo surgery for research purposes. However, the effects of different methods of hair removal on wound healing and surgical site infections (SSI) in rats has not been evaluated. The current study evaluated 2 hair removal methods, clipping with an electric clipper and using a depilatory agent, and their effect on wound healing and SSI. Swabs for bacterial culture were obtained on Day 0 just after hair removal, after aseptic skin preparation, and on Days 1 and 3 before conducting skin biopsies to assess bacterial load and recolonization. Full-thickness punch biopsies were taken for histopathologic evaluation on Days 0, 1, 3, 7, and 10. The surgical incisions were assigned an ASEPSIS score on Days 1 and 3. The data revealed that the bacterial load was significantly higher with the depilatory method as compared with the clipper method, but only on Day 1. The histopathologic evaluation found no significant difference in wound healing between the 2 methods. Although the ASEPSIS score was significantly higher for the clipping method than for the depilatory method on Day 1, both techniques were equivalent by Day 3. We conclude that both hair removal methods are safe and efficacious components of aseptic technique in rats.

Effect of Home Cage Bedding in the Induction Chamber on Serum Cortisol and Corticosterone Levels in Response to Isoflurane-induced Anesthesia in C57BL/6J Mice.

Mice are routinely anesthetized with isoflurane in an induction chamber. The AVMA Guidelines for the Euthanasia of Animals states that distress should be minimized during euthanasia but does not address this point in regard to induction of anesthesia. Here we evaluated the potential for familiar surroundings to reduce the adrenocortical response of mice during anesthesia induction with isoflurane. However, adding bedding from the animals' home cage to the induction chamber failed to significantly reduce serum cortisol or corticosterone levels in male and female C57BL/6J mice. These results indicate that familiar surroundings do not appear sufficient to reduce the adrenocortical response of mice during anesthesia induction with isoflurane.

Evaluation of medicated gel as a supplement to providing acetaminophen in the drinking water of C57BL/6 mice after surgery.

After surgery, rodents frequently receive acetaminophen-treated drinking water for pain relief, but the effectiveness of this practice is often questioned. Gel products are now available to facilitate the delivery of oral medication to rodents after surgery. We sought to compare consumption of flavored medicated gel and medicated water after surgery and to determine whether providing supplemental acetaminophen in gel form ensures the ingestion of a therapeutic dose of an analgesic after surgery. Male C57BL/6 mice were allocated into 3 groups after surgery: those that received acetaminophen-treated water and untreated gel (MW group); those that received medicated gel and untreated water (MG group); and those that received acetaminophen in both forms (MWG group). Total water and gel consumption were monitored daily from the day before surgery until 2 d thereafter. Mice in the MG group consumed significantly less gel than water, and consequently, the total acetaminophen dose per mouse in the MG group (49 mg/kg) was significantly less than that of the MWG group (347 mg/kg). Although the dose consumed by mice in the MW group (158 mg/kg) approached the targeted acetaminophen dose of 200 mg/kg, only mice in the MWG group actually achieved the desired dose. The results of this study indicate that flavored acetaminophen-containing gel can be used in combination with medicated water to ensure that rodents ingest the targeted dose of medication.