Altered circadian rhythms effects on anxiety, locomotor activity, serotonin and nitric oxide levels in the prefrontal cortex of juvenile and adult rats

Abstract

AbstractBackgroundDementia and Alzheimer’s disease (AD) can be exacerbated by irregular sleep‐wake cycles, and age may be a risk factor. This study compared behavioral responses such as anxiety, motor coordination, and locomotion to altered circadian rhythms and serotonin, nitric oxide (NO), and malondialdehyde (MDA) levels in the prefrontal cortex of juvenile and adult rats.MethodA total of thirty female Wistar rats were grouped into three (n = 5) in the following juvenile (30‐45 days old) and adult (90‐120 days old) groups: (A) Control (12L:12D cycle),(B) 24‐hour LED light exposure(12L:12L cycle) and (C) 24‐hour dark cycle (12D:12D cycle). Experimental rats were kept in the stated cycle conditions using natural lighting, LED lighting, and a dark room, respectively, for 60 days. Data were analyzed using a two‐way ANOVA (GraphPad Prism 9), and statistical significance was measured at p<0.05.ResultFindings from the study revealed progressive weight loss in the sleep‐deprived juvenile (12L:12L) rats compared to adults (p<0.05) in the same and other groups. Also, anxiety‐like indices such as longer duration of time in the dark area of the light‐dark box, avoidance of open arm entries on the elevated plus maze, reduced line crossing activity in the open field box, etc. were markedly higher in the juvenile rats from the 12L:12L and 12D:12D groups respectively. When juvenile and adult 12L:12L and 12D:12D cycle rats data were compared to controls, severe depletion of serotonin (p<0.0001) and nitric oxide (p<0.01) levels were observed, while age‐dependent MDA levels were revealed across all groups.ConclusionA bi‐directional relationship was observed between age and circadian disruption effects with more severe outcomes in juveniles compared to adults and this hold interesting implications for the study of the biological clock mechanisms underlying anxiety, mood and sleep disorders in living systems.