Chronic Jet Lag and Its Long-Term Effects on Brain Function Michelle Wrona
Frequent transmeridian travel has the potential to have a detrimental effect on circadian rhythms and brain function. This idea is commonly known as jet lag, which often has a greater influence on travelers undergoing a phase advance, which relates to eastbound travel, instead of phase delays, instigated by westbound travel. Researchers are seeking to determine the effects of chronic jet lag simulation on adult male Sprague Dawley rats. Specifically, they speculate that chronic jet lag negatively influences cognitive and affective behaviours, and hippocampal neurogenesis. The three randomly assigned experimental groups utilized included a control group, phase advancement group, where the light period was shortened by 6 hours, and a phase delay group, whose dark period increased by 6 hours. The light-dark (LD) cycle shifts occurred over a span of eight weeks, with each shift occurring once a week. After the eighth shift, the rats underwent a variety of tests, including: sucrose consumption testing, open field testing, elevated plus maze, forced swim test (FST), and object recognition testing. These tests were conducted to evaluate alterations in emotional behaviour, specifically in anxiety and depression-like symptoms, and to examine short-term memory and learning. It was implied that phase advances had a negative effect on the rats, signifying that it enhances depressive behaviours and deficits in memory. Further discussions showcased that phase advance rats had reduced DCX+ cells in the hippocampus, in addition to disrupted object retention memory. Additionally, symptoms of depression were seen after phase advances. Furthermore, phase delays had little to no effect on the measures examined. Key words: chronic jet lag; light dark (LD) cycle; circadian rhythms; phase advance; phase delay; hippocampal neurogenesis; depression; anxiety
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