Optimization of morris water maze protocols: effects of water temperature and hypothermia on spatial learning and memory in aged female rats

Abstract

Introduction: Aging is a highly complex process driven by a multitude of factors. The use of humans in aging research is complicated by many factors (ethical issues; environmental and social factors; long natural life span). Therefore, rats are common models for the study of aging and age-related diseases. The Morris water maze test is one of the most common cognitive tests in studies investigating age-related learning and memory. However, standardized protocols are lacking, which could influence results. This study investigated the effects of water temperature and inter-trial interval on physiological parameters, hippocampus-dependent learning, and memory in aged female rats performing the Morris Water Maze. Materials and Methods: Thirty-two female Wistar Hannover rats, aged over 18 months, were divided into four groups based on water temperature (20 °C or 24 °C) and inter-trial interval (30 seconds or 13 minutes). Results: Rats exposed to 24 °C demonstrated better spatial learning and memory retention than those at 20 °C. The interaction between inter-trial interval and water temperature significantly affected memory, with higher temperatures improving memory, especially with shorter intervals. Inter-trial interval alone did not significantly affect learning, but longer durations were associated with more stable body temperatures. Neither water temperature nor inter-trial interval significantly influenced body weight. Conclusion: These findings emphasize the need to standardize environmental conditions in Morris water maze protocols to enhance research validity and reliability. Optimizing these protocols is crucial to upholding ethical standards and ensuring animal welfare, advancing more effective and scientifically sound practices in gerontological research, and fostering a better understanding of aging processes.