Strain-dependent differences in neuroplasticity markers related to memory

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 long-term spatial 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. Hippocampal BDNF and DCX protein levels were quantified by Western blotting. 

Results: All strains learned the task, as indicated by a decrease in escape latency and swim distance over time. Sprague Dawley rats swam faster than the other strains, suggesting that swim distance evaluates learning independently of speed. On the first training day, Wistar rats swam the shortest distances, whereas by the final day Long Evans rats did. 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 hippocampal BDNF levels 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 strategies and hippocampal plasticity. Therefore, strain background should be carefully considered when designing and interpreting rodent studies of learning and memory.