Western-style diet induces object recognition deficits and alters complexity of dendritic arborization in the hippocampus and entorhinal cortex of male rats

Abstract

Objective: Research demonstrates a link between diet-induced obesity and cognitive impairments; however, no studies have utilized the Sholl analysis to assess changes in dendritic arborization as a possible cause of obesity-induced memory deficits. Therefore, the purpose of this study was to examine the effect of a Western-style diet (WSD) on memory and dendritic complexity of male Sprague–Dawley rats.Methods: Male Sprague–Dawley rats (n = 18) were fed either a control or WSD. Spatial memory and episodic memory were assessed using the Morris Water Maze and novel object recognition (NOR) tasks, respectively. At termination, brains were removed and prepared with the Golgi-Cox method. Stained neurons in both the hippocampus and entorhinal cortex (EC) were imaged and digitally reconstructed.Results: Results indicated significant differences in percent body fat and TNFα levels between dietary conditions. WSD males also experienced reduced NOR exploration ratios, but no deficits in spatial memory were observed. Analysis of dendritic length and number of branch points revealed no significant differences in either the EC or the hippocampus; however, the Sholl analysis indicated that a WSD increased neuronal complexity in the EC.Discussion: Sholl analysis of the EC suggests a possible diet-induced dysfunction of pruning, which may contribute to reduced performance on the NOR task. Elevated TNFα levels indicate a putative role of inflammation in neuronal remodeling. The results demonstrate the importance of investigating mechanisms underlying obesity-related cognitive impairments.