Superiority of Combined Endurance-Resistance Exercise for Increasing the Molecular and Pyramidal Layers Thickness of Hippocampal Tissue in Alzheimer\'s Laboratory Large White Rats

Introduction: The thickness of the molecular and pyramidal layers in the hippocampus represents a pivotal aspect of Alzheimer's research. This study was conducted to investigate the effect of swimming endurance, resistance, and combined exercises on the molecular and pyramidal layers of the hippocampus tissue thickness of Alzheimer's rats. Methods: In this experimental study, 40 large white Wistar laboratory rats (6 weeks old; Weight 180-200 g) were randomly and equally divided into five groups: healthy control, Alzheimer's control, endurance, resistance, and combined. Alzheimer's disease was induced by intraperitoneal injection of trimethyltin chloride (8 mg/kg). Two weeks after the injection and confirmation of Alzheimer's induction, the training protocols of endurance (5-sessions/week, the first to the fourth week incrementally from 5-15-min to 45-min of swimming, the fifth to the twelfth week 60-min of swimming), resistance (5-sessions/week, The first week of familiarization with the exercise, week 2; 30%, week3-5; 70-90%, week6-8; 100-110%, week9-10; 120-130%, and week11-12; 140-150% of body weight), combined (2 resistance sessions/week and three endurance sessions/week) was performed for 12 weeks. Forty-eight hours post-intervention, animals were dissected, and hippocampus tissue was harvested. Finally, the data were analyzed at the significance level of P < 0.05. Results: The thickness of the molecular and pyramidal layers of the hippocampal tissue of Alzheimer's animals decreased compared to healthy animals, and all three endurance, resistance, and combined exercise protocols increased layers (P < 0.001). However, the increase in the molecular and pyramidal layers thickness of the hippocampal tissue of combined group rats compared to the endurance and resistance group had a greater increase (P < 0.01). Conclusions: These findings highlight the changes in the thickness of the hippocampal tissue layers concerning Alzheimer's pathology and the effect of combined exercises on this parameter. While exercise may have positively affected hippocampal volume and synaptic plasticity, more research is needed to fully understand the impact of exercise on hippocampal layer thickness in Alzheimer's.