Evaluation of alfaxalone total intravenous anesthesia in rabbits (Oryctolagus cuniculus) premedicated with dexmedetomidine or dexmedetomidine and buprenorphine.

OBJECTIVE: To evaluate alfaxalone for total intravenous anesthesia (TIVA) in rabbits premedicated with dexmedetomidine or dexmedetomidine and buprenorphine. STUDY DESIGN: Crossover study (part 1) with observational study (part 2). ANIMALS: A total of eight New Zealand White rabbits (Oryctolagus cuniculus), four female and four male, aged 12-16 weeks and weighing 2.8-3.5 kg in part 1. Separately, four additional rabbits in part 2. METHODS: Crossover study design with eight rabbits per treatment. Rabbits were administered treatment D, dexmedetomidine (0.2 mg kg-1), or treatment DB, dexmedetomidine (0.1 mg kg-1) and buprenorphine (0.05 mg kg-1) intramuscularly. Anesthesia was induced with alfaxalone intravenously until a supraglottic airway device was placed to deliver 100% oxygen. Anesthesia was maintained with alfaxalone (TIVA). Infusion rates were adjusted to achieve an absent pedal withdrawal reflex. Heart rate, respiratory rate, noninvasive blood pressure, end-tidal carbon dioxide partial pressure and peripheral hemoglobin oxygen saturation (SpO2) were recorded every 5 minutes. Subsequently, four rabbits underwent ovariohysterectomy using treatment DB and alfaxalone TIVA. RESULTS: The mean ± standard deviation alfaxalone infusion rate was 9.6 ± 2.6 and 4.5 ± 1.3 mg kg-1 hour-1 for treatments D and DB, respectively. In both treatments, blood pressure remained within acceptable range and SpO2 was > 95%. Postinduction apnea and respiratory depression were observed in both treatments and managed with manual positive pressure ventilation. Four separate rabbits underwent successful ovariohysterectomy with treatment DB and alfaxalone TIVA. One rabbit required supplementation with inhalant anesthesia; three rabbits were successfully maintained using alfaxalone TIVA alone. CONCLUSIONS AND CLINICAL RELEVANCE: Premedication with dexmedetomidine-buprenorphine combined with alfaxalone TIVA may be a viable alternative for performing abdominal surgery in the rabbit. The use of supplemental oxygen and ability to provide respiratory support are advised.

Effects of subcutaneous alfaxalone alone and in combination with dexmedetomidine and buprenorphine in guinea pigs (Cavia porcellus).

OBJECTIVE: To characterize alfaxalone administered subcutaneously (SC) in guinea pigs, both alone and in combination with dexmedetomidine and buprenorphine. STUDY DESIGN: Prospective, blinded, crossover study. ANIMALS: A total of 15 healthy female guinea pigs weighing 400-600 g. METHODS: Alfaxalone (10, 20 and 40 mg kg-1) was administered SC to three guinea pigs as a pilot dose-finding study. Alfaxalone (20 mg kg-1; A20) was selected for comparison against combination protocols of alfaxalone (15 and 20 mg kg-1) with dexmedetomidine (0.25 mg kg-1) and buprenorphine (0.05 mg kg-1; A15DB, A20DB). Each protocol was randomly administered to 12 guinea pigs separated by ≥7 days. Time and quality of induction and recovery, heart rate, respiratory rate, peripheral hemoglobin oxygen saturation, rectal temperature, pedal withdrawal reflex and adverse effects were recorded. RESULTS: The median time to induction for A20, A15DB and A20DB was 6.8-8.0 minutes with no significant difference between treatments. Mean duration of recumbency for A20 was 73.6 ± 19.6 minutes. Recumbency duration for A15DB and A20DB extended to 90 minutes, at which time dexmedetomidine was antagonized using atipamezole (0.025 mg kg-1 SC). Physiological variables were within normal limits with the exception of one animal that died 45 minutes following treatment with A20DB. Pedal withdrawal reflex remained intact with all treatments. Minor side effects such as twitching or bruxism occurred sporadically with treatment A20 but not with A15DB and A20DB. CONCLUSIONS AND CLINICAL RELEVANCE: SC alfaxalone produced uncomplicated sedation that may be recommended for nonpainful procedures that do not require complete immobility. The addition of dexmedetomidine and buprenorphine increased the duration of sedation and immobility, but did not result in general anesthesia. This combination sedation protocol may be useful for nonpainful procedures requiring extended immobility.

Estradiol- and Progesterone-Associated Changes in microRNA-Induced Silencing and Reduced Antiseizure Efficacy of an Antagomir in Female Mice.

About one-third of individuals living with epilepsy have treatment-resistant seizures. Alternative therapeutic strategies are thus urgently needed. One potential novel treatment target is miRNA-induced silencing, which is differentially regulated in epilepsy. Inhibitors (antagomirs) of specific microRNAs (miRNAs) have shown therapeutic promise in preclinical epilepsy studies; however, these studies were mainly conducted in male rodent models, and research into miRNA regulation in females and by female hormones in epilepsy is scarce. This is problematic because female sex and the menstrual cycle can affect the disease course of epilepsy and may, therefore, also alter the efficacy of potential miRNA-targeted treatments. Here, we used the proconvulsant miRNA miR-324-5p and its target, the potassium channel Kv4.2, as an example to test how miRNA-induced silencing and the efficacy of antagomirs in epilepsy are altered in female mice. We showed that Kv4.2 protein is reduced after seizures in female mice similar to male mice; however, in contrast to male mice, miRNA-induced silencing of Kv4.2 is unchanged, and miR-324-5p activity, as measured by the association with the RNA-induced silencing complex, is reduced in females after seizure. Moreover, an miR-324-5p antagomir does not consistently reduce seizure frequency or increase Kv4.2 in female mice. As a possible underlying mechanism, we found that miR-324-5p activity and the silencing of Kv4.2 in the brain were differentially correlated with plasma levels of 17ß-estradiol and progesterone. Our results suggest that hormonal fluctuations in sexually mature female mice influence miRNA-induced silencing and could alter the efficacy of potential future miRNA-based treatments for epilepsy in females.

Intramuscular Administration of Alfaxalone Alone and in Combination for Sedation and Anesthesia of Rabbits (Oryctolagus cuniculus).

This study compared alfaxalone, alone and in combination with other medications, for sedative and anesthetic properties after intramuscular administration in New Zealand white rabbits. In the main portion of the study, 6 female rabbits were assigned to 5 treatment regimens in a blinded crossover design. Alfaxalone (6 mg/kg IM) was administered alone and in combination with each of the following: 0.3 mg/kg butorphanol; 1 mg/kg midazolam; 0.2 mg/kg dexmedetomidine; and both 0.3 mg/kg butorphanol and 0.2 mg/kg dexmedetomidine. An additional 6 rabbits received 0.2 mg/kg dexmedetomidine for comparison. The median time to onset of recumbency ranged from 2.0 to 5.5 min, with times significantly shorter for animals that received alfaxalone with either midazolam or dexmedetomidine than for those given dexmedetomidine only. Duration of sedation (mean ± 1 SD) was: alfaxalone only, 40 ± 7.3 min; alfaxalone with butorphanol, 47.8 ± 9.9 min; alfaxalone with midazolam, 65.2 ± 6.5 min; alfaxalone with dexmedetomidine, 157.5 ± 22.4 min; alfaxalone with butorphanol and dexmedetomidine, 157.7 ± 22.3 min, and dexmedetomidine only, 93.7 ± 11.9 min. Response to noxious stimuli was absent in 2 of the rabbits given dexmedetomidine only, 4 of those given alfaxalone with dexmedetomidine, and all 6 of the animals dosed with alfaxalone, butorphanol, and dexmedetomidine; this last group displayed the longest absence of a toe-pinch response (57 ± 3 min).

Assessment of Mouse Handling Techniques During Cage Changing.

Mouse handling during cage changing and health evaluation has traditionally been performed by using forceps. This method was adopted as a biosecurity measure but can adversely affect employee ergonomics and rodent behavior. In this study, we evaluated alternative methods of rodent handling and their potential implications for efficiency, biosecurity, and animal welfare. Study groups included plastic cups, gloved hands, 2 methods of tunnel handling, and forceps. Evaluations included speed of cage change, ATP-based assessment of sanitization, and retrospective analysis of colony health and breeding data. The time to change 14 cages was significantly faster at each time point for the gloved hands and forceps groups as compared with the other methods. Overall speed did not increase significantly with each subsequent study week for any group. ATP levels after sanitization with hydrogen peroxide-peracetic acid mixture differed significantly between gloves and forceps. When ATP level was evaluated on a per-cm² basis, no significant difference between gloves and forceps was detected. Although tunnel and cup handling both increased the time for cage-changing, the tunnel served as both an indirect handling method and a shelter when left within the cage. Retrospective analysis revealed that breeding performance and colony health were similar among groups. Although efficiency is a concern for large-scale implementation of novel handling methods, the tunnel method may prove beneficial for sensitive strains or studies requiring indirect handling. In addition, using gloved hands to directly handle mice during cage changing is efficient and avoids the ergonomic strain associated with forceps. Precautions should be taken when handling mice with gloves, given that the increased contact area carries an increased load of organic debris. Changing gloves between rack sides or before proceeding to the animals belonging to a different investigator minimizes the potential for cross-contamination.

Refinement of Perioperative Feeding in a Mouse Model of Vertical Sleeve Gastrectomy.

Provision of liquid enteral nutrition (LEN) during the perioperative period is standard practice for rodents undergoing bariatric surgery, yet these diets are associated with several challenges, including coagulation of the liquid diet within the delivery system and decreased postoperative consumption. We investigated the use of a commercially available high-calorie dietary gel supplement (DG) as an alternative food source for mice during the perioperative period. C57BL/6J male mice were fed high-fat diet for 8 to 10 wk prior to surgery. The study groups were: vertical sleeve gastrectomy (VSG) +DG, VSG+LEN, sham surgery+DG, and sham+LEN. Food and water intakes, body weight, and body fat composition was monitored throughout the study. Mice that received DG lost significantly more weight preoperatively than those fed LEN. However, during the postoperative period, body weight, body fat composition, and water and caloric intake were similar among all experimental diet groups. Three mice in the VSG+LEN group were euthanized due to clinical illness during the course of the study. In summary, feeding a high-calorie DG to mice undergoing VSG surgery is a viable alternative to LEN, given that DG does not significantly affect the surgical model of weight loss or result in adverse clinical outcomes. We recommend additional metabolic characterization of DG supplementation to ensure that this novel diet does not confound specific research goals in the murine VSG model.