Intraperitoneal Alfaxalone and Alfaxalone–Dexmedetomidine Anesthesia in Sprague–Dawley Rats (Rattus norvegicus)

Due to their unpredictability and variable effects, injectable anesthetic regimens in laboratory rodent species warrant refinement. In our study we sought to evaluate alfaxalone, which has gained recent popularity in veterinary medicine, alone and in combination with dexmedetomidine to evaluate their anesthetic ability in Sprague–Dawley rats when administered intraperitoneally. Three doses of alfaxalone only and 4 dose combinations of alfaxalone-dexmedetomidine were tested in males and female rats. The time to induction, anesthetic duration, pulse rate, respiratory rate, temperature, and time to recovery were recorded by a blind observer. The level of anesthesia induced by the various anesthetic protocols was assessed by using pedal withdrawal reflex to a noxious stimulus and scored according to the response. Dependent on the treatment group, atipamezole or saline was administered intraperitoneally once animals reached 60 min of anesthesia. Regardless of the dose, alfaxalone alone achieved only a sedative level of anesthesia, whereas all alfaxalone-dexmedetomidine combinations led to a surgical level of anesthesia in all animals. Anesthesia regimens using alfaxalone alone and in combination with dexmedetomidine demonstrated sex-associated differences, with female rats maintaining longer durations of sedation or anesthesia than their male counterparts. Both male and female rats displayed decreases in physiologic parameters consistent with the effects of dexmedetomidine. Given the results described herein, we recommend 20 mg/kg alfaxalone for sedation and 30 mg/kg alfaxalone combined with 0.05 mg/kg dexmedetomidine for surgical anesthesia in female rats. Appropriate doses of alfaxalone only and alfaxalone-dexmedetomidine for male rats were not determined in this study and need further evaluation.

MOLECULAR CHARACTERIZATION OF TWO NOVEL RAT MINUTE VIRUSES IN TAIWAN

Rodent parvovirus infection is one of the common viral problems in laboratory rodent colonies. In this study, two new parvoviruses were identified in naturally-infected rats from two different research colonies in Taiwan. The genomic nucleotide sequences and the predicted amino acid sequences of proteins for these two viruses were compared to the previously characterized rodent parvoviruses. The two newly identified viruses were most closely related to each other, also closely related to two variants of rat minute virus (RMV; RMV-1 and RMV-2), and distinct from but closely related to Kilham rat virus and H-1 virus. These two viruses were significantly different from variants of rat parvovirus (RPV; RPV-1 and RPV-NTU1). Phylogenetic data also supported that these two new viruses are variants of the RMV species. These two newly identified viruses were designated RMV type National Taiwan University 1 (RMV-NTU1) and RMV type National Taiwan University 2 (RMV-NTU2). RMV-NTUs are the first molecularly characterized RMV variants identified in Asia.

Choice of Laboratory Rodent Diet May Confound Data Interpretation and Reproducibility

ABSTRACT The reproducibility of experimental data is challenged by many factors in both clinical and preclinical research. In preclinical studies, several factors may be responsible, and diet is one variable that is commonly overlooked, especially by those not trained in nutrition. In particular, grain-based diets contain complex ingredients, each of which can provide multiple nutrients, non-nutrients, and contaminants, which may vary from batch to batch. Thus, even when choosing the same grain-based diet used in the past by others, its composition will likely differ. In contrast, purified diets contain refined ingredients that offer the ability to control the composition much more closely and maintain consistency from one batch to the next, while minimizing the presence of non-nutrients and contaminants. In this article, we provide several different examples or scenarios showing how the diet choice can alter data interpretation, potentially affecting reproducibility and knowledge gained within any given field of study.

A Review of Pain Assessment Methods in Laboratory Rodents

Ensuring that laboratory rodent pain is well managed underpins the ethical acceptability of working with these animals in research. Appropriate treatment of pain in laboratory rodents requires accurate assessments of the presence or absence of pain to the extent possible. This can be challenging some situations because laboratory rodents are prey species that may show subtle signs of pain. Although a number of standard algesiometry assays have been used to assess evoked pain responses in rodents for many decades, these methods likely represent an oversimplification of pain assessment and many require animal handling during testing, which can result in stress-induced analgesia. More recent pain assessment methods, such as the use of ethograms, facial grimace scoring, burrowing, and nest-building, focus on evaluating changes in spontaneous behaviors or activities of rodents in their home environments. Many of these assessment methods are time-consuming to conduct. While many of these newer tests show promise for providing a more accurate assessment of pain, most require more study to determine their reliability and sensitivity across a broad range of experimental conditions, as well as between species and strains of animals. Regular observation of laboratory rodents before and after painful procedures with consistent use of 2 or more assessment methods is likely to improve pain detection and lead to improved treatment and care—a primary goal for improving overall animal welfare.

The Measurement of Pain in the Laboratory Rodent

The current translational crisis, in which apparently rapidly expanding genetic, molecular, and cellular knowledge has not resulted in novel clinical therapies, has forced preclinical pain researchers to question the algesiometric status quo. One hypothesized cause of poor translation is the limited external validity of the reflexive withdrawals to evoking stimuli that represent the ubiquitous dependent measures of pain at the present time. As a response, new techniques have been developed and are increasingly being incorporated into pain studies. This comprehensive review examines the subjects, assays, and measures used in preclinical pain research, as well as the need for and implementation of newly described measures of spontaneous, ongoing chronic pain.