Chronic Unpredictable Mild Stress Causing Cardiac and Thoracic Spinal Cord Electrophysiological Abnormalities May Be Associated with Increased Cardiac Expression of Serotonin and Growth-Associated Protein-43 in Rats

Figures

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  Figure 1. General procedure in this study. The nine types of environmental stressors for the CMS group. (1) Behavior restrictions; (2) overnight lighting; (3) tilted cage for 24 h; (4) clustered feeding; (5) ice water swimming; (6) day and night reversal; (7) soiled cage; (8) wet cage; and (9) noise stimulation. The stressful stimulus was given at 8:00 a.m. every morning, and the stimuli were applied in a random order to ensure the animals could not predict the stimulus to be used. A total of nine types of stimuli were applied, and the stimulus type was randomly assigned each day. The control group of animals was housed for the same period of time (three weeks) without exposure to stressful stimuli. n = 10/group.

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  Figure 2. Weight and residual food content in the stomach. (a) The weight of the animals of the two groups was similar at baseline and 1 week, but the CMS group showed no weight gain at 2 and 3 weeks, while the control group gained body weight (P < 0.01). (b) The CMS group showed higher gastric food residues than the control group (P < 0.01). n = 10/group. ∗∗P < 0.01 compared with control group.

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  Figure 3. Indicators of stress in rats. (a) Consumption of sucrose solution normalized to body weight and preference for the consumption of sucrose solution. (b) Horizontal and vertical movement score during the open field test. ∗P < 0.01. n = 10/group.

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  Figure 4. Representative examples of field action potentials recorded from localized regions of cardiac atrial and ventricular tissue. (a) Atrial field action potentials in the control group. (b) Atrial field action potentials in the CMS group. (c) Ventricular field action potentials in the control group. (d) Ventricular field action potentials in the CMS group. (e) Quantification of atrial field action potentials. (f) Quantification of ventricular field action potentials. (g) Quantification of heart rates. ∗P < 0.01. n = 10/group.

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  Figure 5. Representative examples of field action potentials recorded from T1–5 spinal cord. (a) T1–5 spinal cord field action potentials (500 mV stimulation) in the control group. (b) T1–5 spinal cord field action potentials (500 mV stimulation) in the CMS group. (c) T1–5 spinal cord field action potentials (1000 mV stimulation) in the control group. (d) T1–5 spinal cord field action potentials (1000 mV stimulation) in the CMS group. (e) Quantification of the T1–5 spinal cord field action potentials at 500 mV stimulation. (f) Quantification of the T1–5 spinal cord field action potentials at 1000 mV stimulation. ∗P < 0.01. n = 10/group.

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  Figure 6. Expression of 5-hydroxytryptamine (5-HT) in cardiac ventricular tissue. (a-b) Representative examples, obtained using immunohistochemistry techniques to stain for 5-HT, are shown. (a) Control group. (b) CMS group. Magnification: ×200. (c) Quantification of the positive reaction area. (d) Quantification of the positive intensity value. (e) Quantification of the positive index. ∗P < 0.01. n = 10/group.

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  Figure 7. GAP-43 expression in cardiac ventricular tissue. (a) Representative examples, obtained using immunohistochemistry techniques to stain for GAP-43, are shown. Left: control group. Right: CMS group. Magnification: ×200. (b) Quantification of the fiber bands stained. ∗P < 0.01 compared with control group.