Abstract
It has been documented that constant light exposure exerts complicated cardiovascular effects. However, a mounting collection of conflicting results did not make it any easier for researchers and physicians to consider the role of light on cardiovascular function. This study was designed to investigate how constant light exposure (24 h light/day) influences the cardiac function in normal and heart-failure (HF) rats. In normal rats, two groups of SD rats were accustomed in 12 h light/12 h dark (LD) or 24 h light (constant light, CL) for 4 weeks. In HF rats which was induced by myocardial infarction (MI) was let recover in LD for 4 weeks. Interestingly, compared with rats in LD environment (ejection fraction, EF%: 93.64 ± 2.02 in LD, 14.62 ± 1.53 in HF-LD), constant light (2 weeks) weakened the cardiac function in normal and HF rats (EF%: 79.42 ± 2.91 in CL, 11.50 ± 1.08 in HF-CL). The levels of renal sympathetic nerve activity and c-fos expression in the rostral ventrolateral medulla (RVLM), a key region controlling sympathetic outflow, were significantly increased in normal and HF rats after constant light (RSNA, Max%: 8.64 ± 0.48 in LD, 20.02 ± 1.24 in CL, 20.10 ± 1.16 in HF-LD, 26.82 ± 1.69 in HF-CL). In conclusion, it is suggested that constant light exposure exerts detrimental cardiovascular effects, which may be associated with the RVLM-related sympathetic hyperactivity.
Highlights
Environmental stimuli have a universal influence on humans
Heart and brain were collected and fixed with 4% PFA overnight at 4◦C. 20% Sucrose solution was used for Validation of Heart Failure Model in Rats
The myocardial infarction (MI) procedure was verified by EchCG and intraventricular pressure recording, the cardiac function was significantly reduced after MI (Table 1)
Summary
Environmental stimuli have a universal influence on humans. Environmental light can greatly affect health in a time-, wavelength-, and intensity-related manner (Tapia-Osorio et al, 2013; Alves-Simoes et al, 2016; Barba et al, 2018). The use of light-emitting electronic devices has Detrimental Effect of Constant Light dramatically increased recently, leading to a broad influence in health, and safety (Chang et al, 2015). The relationship between prolonged light exposure and cardiovascular events was well studied (Furlan et al, 2000; Martino et al, 2007; Morris et al, 2016; Reynolds et al, 2017; Singh et al, 2019). Constant light exposure was able to influence people’s behavior and health, making adverse effects on the cardiovascular system reportedly (Furlan et al, 2000; Chang et al, 2015; Reynolds et al, 2017; Benedetto and Contin, 2019; Bohmer et al, 2019). A systematic study on constant light is of unquestionable importance for people with cardiovascular illness
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