Abstract

Aim: Spatial learning and memory both rely critically on hippocampal plasticity which are a core feature of several neurological and psychiatric disorders, but commonly used different rat strains might exhibit differences in these processes which may influence the translational relevance of preclinical findings Herein, we examined the spatial long-term memory of adult Wistar (n=5), Sprague Dawley (n=6), and Long Evans (n=5) rats, and their hippocampal expression of two plasticity markers: brain-derived neurotrophic factor (BDNF) and doublecortin (DCX).
Materials and Methods: The animals were trained in the Morris water maze for four days, followed by a probe trial with no platform. The levels of hippocampal BDNF and DCX proteins were quantified by Western-blotting.
Results: All strains learned the task, as indicated by decreasing escape latency and swim distance over time. Sprague Dawley rats swam faster than the other strains, suggesting that swim distance evaluate learning independently of speed. On the first training day, Wistar rats swam the shortest distances, whereas Long Evans rats swam the shortest distances by the final day. In the probe trial, Sprague Dawley rats spent a greater proportion of time in the target quadrant than Wistar rats did. Long Evans rats displayed an intermediate pattern. At the molecular level, Sprague Dawley rats had higher BDNF levels in the hippocampus than Wistar and Long Evans rats. DCX levels were higher in Sprague Dawley and Long Evans rats than in Wistar rats.
Conclusion: These findings suggest that although all three strains can acquire and retain spatial memory under identical conditions, they differ in behavioral strategy and hippocampal plasticity. Therefore, strain background should be carefully considered when designing and interpreting rodent studies of learning and memory.

Key words: BDNF, DCX, Morris Water Maze, Rat Strains, Spatial Learning and Memory.