The effects of high intensity exercise on learning and memory impairments followed by combination of sleep deprivation and demyelination induced by etidium bromide

Abstract

Introduction: Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. Cognitive impairments occurs in MS patients including learning and memory impairments. More than 50% of MS patients suffer from sleep problems. It has been suggested that in animal models exercise has direct neuroprotective effects on MS and sleep deprivation (SD). In this research, MS impairments were induced using a demyelination model as an indicator of MS disease. Also induction of SD was done using multiple platform. In order to focus on the research question, combination of MS model with SD was studied. In this study, the impact of treadmill exercise on learning and memory impairments was investigated.

Material and methods: Male wistar rats were used in the present study. Exercise groups exercised daily for 1?h/day for 10 consecutive days with treadmill (speed: 18?m/min and inclination: 25°). The multiple platform method was applied for the induction of a 72?h SD. The cognitive functions were evaluated using Morris water maze (MWM) and open field tests. Animals were anaesthetized with a certain dose of ketamine and xylazin. After full anesthesia, the rat was placed on rat stereotaxic instrument in the skull-flat position. Demyelination was induced bilaterally by direct single injection of 3?µl of 0.01% ethidium bromide in sterile 0.9% saline at the rate of 1?µl/min into the hippocampal formation. The dose was injected using appropriate stereotaxic coordinates.

Results: All of the learning and memory indices in the MWM task showed that SD and hippocampal demyelination destroy learning and memory. It seems that exercise can modulate the destructive effects of SD and demyelination on learning and memory at the behavioral level.