Learning and memory assessment in rodents: Testing strategies for post-weaning rats

BDRP 2025 -- The U.S. EPA OPPTS 870.6300 Test Guideline (TG), the OECD 426 TG, and potential additions to OECD 443 TG emphasize the need for test batteries assessing learning and memory function in rodents at weaning and adulthood. While cognitive testing methods are well established for adult animals, assessing learning and memory in younger animals presents challenges due to their physical immaturity, sensitivity to handling, and heightened stress levels, resulting in greater data variability. Therefore, validating equipment and optimizing test procedures through positive control studies is crucial for obtaining reliable and reproducible data. Using scopolamine as a positive control, we optimized and validated Morris water maze (MWM) and Biel water maze (BWM) testing conditions for postweaning [post-natal day (PND) 25±2] Sprague Dawley® and Han® Wistar rats as two testing options based on allocentric and egocentric spatial processing.