Effect of forced treadmill exercise on stimulation of BDNF expression, depression symptoms, tactile memory and working memory in LPS-treated rats

Abstract

Neuroinflammation has been implicated in cognitive dysfunction and the occurrence of depression in neurodegenerative diseases. Brain-derived neurotrophic factor (BDNF) is believed to be involved with the benefits of exercise training in boosting memory and learning processes and antidepressant therapies. This study aimed to investigate the effect of forced treadmill exercise on hippocampal BDNF expression levels, depression symptoms, tactile memory and working memory in lipopolysaccharide (LPS)-treated rats. For this purpose, 40 male Wistar rats received 0.25 mg/kg of LPS or saline intraperitoneally for 9 consecutive days before exercise. They again received a single injection of 0.5 mg/kg of LPS or saline on days 20 and 41 after exercise. Exercise groups had to run on a motorized treadmill 5 days a week for 8 weeks. Following the last exercise training session, forced swim test (FST), Y maze and novel object recognition (NOR) task were performed. Finally, the hippocampus of rats was removed and used for determination of BDNF expression levels by real-time polymerase chain reaction (real-time PCR). The data showed that LPS decreased BDNF expression levels, Y maze score, and recognition index in NOR and increased immobility time in FST (p < 0.05). In contrast, forced treadmill exercise increased BDNF expression levels and improved the percentage of spontaneous alternation, recognition index, and immobility time in LPS-treated rats (p < 0.05). There was a significant correlation between BDNF expression levels with immobility time and recognition index (p < 0.05) but not with the percentage of spontaneous alternation (p > 0.05). The findings suggest that forced treadmill exercise may protect the brain of LPS-treated rats by improving the symptoms of depression and cognitive function through its effect on BDNF expression levels.