Constant Light Exerted Detrimental Cardiovascular Effects Through Sympathetic Hyperactivity in Normal and Heart Failure Rats

Figures

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  FIGURE 1. Experiment timeline. (A) Schematic design of normal rats in LD/CL. SD rats were accustomed under LD or CL for 4 weeks. In the first week, BP in conscious conditions was measured with tail-cuff system. EchCG was employed in the end for cardiac function. (B) Schematic flowchart of HF-LD/HF-CL rats. MI procedure was performed in LD rats and validated by EchCG 4 weeks later. A decrease of EF by 50% was considered HF. Rats were then randomly grouped into two, accustomed under LD or CL for another 2 weeks, in which dynamically monitoring of cardiac function by EchCG was employed in the following 2 weeks. Eventually, rats were sacrificed for intraventricular pressure and RSNA recording.

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  FIGURE 2. Histology and EchCG evidence after MI. The images from the Histology column showed the eosin staining of the heart from sham and HF rats. Bar = 500 μm. The right two images were representative recordings of the EchCG, from which some of the cardiac function parameters were extracted.

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  FIGURE 3. The effect of constant light on cardiac function in normal and HF rats. (A) BP measured by tail-cuff system in conscious LD and CL rats. n = 6. (B) EF acquired by EchoCG dynamical monitoring in HF-LD or HF-CL rats. Day 0 was the day when MI was performed. From Day 0 to day 28, rats were let recover from MI in LD. From day 28 on, rats were housed in LD or CL for 2 weeks in HF-LD or HF-CL rats, respectively. n = 5. (C) Representative images of left ventricular heart sections stained with Masson staining at ×400 magnification. Scale bars = 100 μm. n = 5. Results are performed using one-way ANOVA. *P < 0.05, **P < 0.01, &P < 0.001, § P < 0.0001 vs. LD. $P < 0.001, ¥P < 0.0001 vs. HF-LD.

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  FIGURE 4. Plasma NE, MAP and baseline RSNA of normal and HF rats. (A) Plasma NE concentration (n = 5) in four groups; (B,C), MAP and baseline RSNA (%Max) (n = 3) statistical diagraphs. *P < 0.05, **P < 0.01, &P < 0.001, § P < 0.0001 vs. LD. #P < 0.05 vs. HF-LD.

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  FIGURE 5. c-fos expression in the RVLM of LD, CL, HF-LD, and HF-CL rats. (A) Top: representative IHC-DAB staining of c-fos. Scale bars = 100 μm. Brown showed c-fos expression, and purple for cell nucleus. Bottom: IF-GFP staining of c-fos. Scale bars = 50 μm. Green fluorescence showed c-fos. (B) The location of RVLM in brain atlas. (C) Percentage of c-fos positive cells in RVLM. Values were extracted from IHC-DAB (A, top). **P < 0.01, § P < 0.001 vs. LD. ¥P < 0.0001 vs. HF-LD. n = 5.

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  FIGURE 6. Constant light exposure disrupted circadian rhythm of spontaneous activity, plasma melatonin and corticosterone. (A) Left: the spontaneous activity in 24 cycles was recorded by remote sensing monitoring; Right: the average activity difference between ZT12-24 and ZT0-12 in LD and CL groups (n = 3). *P < 0.05 vs. ZT12-24 in LD. (B) The plasma melatonin and corticosterone level (n = 5). Melatonin: **P < 0.01, § P < 0.0001 vs. ZT12-24 in LD. Corticosterone: *P < 0.05, § P < 0.0001 vs. ZT12-24 in LD; ¥P < 0.0001 vs. ZT0-12 in LD.