Development of behavioral patterns in young C57BL/6J mice: a home cage-based study

Abstract

Evidence exists that behavioral patterns only stabilize once mice reach adulthood. Detailed information about the course of behavioral patterns is of particular relevance for neuroscientific research and for the assessment of cumulative severity in genetically modified mice. The analysis considered five age groups focusing on behavioral assessments in the animals’ familiar home cage environment during the adolescence phase. We confirmed age- and sex-specific differences for several of the behavioral parameters and fecal corticosterone metabolites. Interestingly, an age-dependent decline in saccharin preference was detected in female mice. Regardless of sex, relevant levels of burrowing activity were only observed during later developmental phases. The development of nest complexity following the offer of new material was affected by age in female mice. In female and male mice, an age-dependency was evident for wheel running reaching a peak at P 50. A progressive increase with age was also observed for Open field activity. The data sets provide guidance for behavioral studies and for development of composite measure schemes for evidence-based severity assessment in young mice. Except for the burrowing test, the different behavioral tests can be applied in different age groups during post-weaning development. However, age- and sex-specific characteristics need to be considered.

Phenotyping Young GluA1 Deficient Mice – A Behavioral Characterization in a Genetic Loss-of-Function Model

“…The preference for sweetness can be interpreted to reflect anhedonia-associated behavioral traits in laboratory rodents (Crawley, 2006;Klein et al, 2015). As described previously (Reiber et al, 2022), mice received two water bottles filled with 200 g tap water on the first and third day during the two observation periods in order to assess the water intake 2 www.randomizer.org over 24 h. On day 2 and 4, one water bottle was filled with 200 g of a 0.1% saccharin solution (Aldrich Saccharin ≥ 98%, Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany). The other bottle contained 200 g of tap water.…”

“…Since we have detected relevant levels of burrowing activity in adolescent wild-type mice once the animals reached sexual maturity (Reiber et al, 2022), we applied the burrowing test in sexually mature mice only. We analyzed the burrowing performance assessing the weight of food pellets burrowed by the animals in their home cages during a 2-h light-phase session and thereafter once again during the dark phase overnight.…”

“…As described previously (Reiber et al, 2022), we assessed nest building performance in the home-cage, analyzing the complexity and shape of the nest over an observation period of 4 days each in prepubescent and sexually mature mice. Mice received two pressed cotton squares per home cage.…”

“…The applied behavioral and biochemical composite measure scheme was derived from an extensive dataset of consortium data for the purpose of severity assessment in different adult rodent models (Bleich et al, 2020). Our group has further figured out the parameters rendering the highest informative value based on a bioinformatic approach (Keubler et al, 2020;van Dijk et al, 2020), and we subsequently have evaluated their versatile applicability in adolescent C57BL/6J wild-type mice (Reiber et al, 2022). Despite the aspect of ethical responsibility that researchers bear, animal welfare assessments are mandatory according to Directive 2010/63/EU.…”

“…GluA1 deficient mice of the strain B6N.129-Gria1 TM1Rsp represent a loss-of-function model of neuropsychiatric relevance, which has been classified to experience "no harm burden." However, following the guidelines provided by the German Centre for the Protection of Laboratory Animals (Bf3R), the entire developmental phase of the mice between weaning in late infancy and young adulthood is not necessarily involved when investigating severity grading of genetically modified lines (EU, 2010;Bf3R, 2016;Reiber et al, 2022). Ethologically-based characterization, comprising cross-model, cross-species and cross-age validations, allow for conclusions about face validity (Percie du Sert et al, 2020), adequate refinement measures and welfare-based model prioritization (van Dijk et al, 2020).…”