The Diurnal Profile of Human Basal Pain Sensitivity and Skin Sympathetic Nerve Activity: A Healthy Volunteer Study

Figures

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  FIGURE 1. Flow chart of the study. (A) Each subject was tested in the chronological order from test point 1 to test point 6. (B) Each parameter was measured according to the listed sequence.

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  FIGURE 2. The pilot experiment based on laboratory members. (A–D) Show the change trend of the experimental pain thresholds (including PPT, PTO, CPT and CTO) at the six time points. Data are presented as mean ± standard deviation. PPT, pressure pain threshold; PTO, pressure pain tolerance; CPT, cold pain threshold; CTO, cold pain tolerance.

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  FIGURE 3. Values of pressure pain threshold (A), pressure pain tolerance (B), cold pain threshold (C), and cold pain tolerance (D) at six time points in a day (08:00, 12:00, 16:00, 20:00, 00:00, 04:00). Data are represented as mean value and standard error. ∗∗P < 0.01. PPT, pressure pain threshold; PTO, pressure pain tolerance; CPT, cold pain threshold; CTO, cold pain tolerance.

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  FIGURE 4. The mean values of average skin sympathetic nerve activity (A), mean arterial pressure (B), heart rate (C), peripheral vascular resistance (D), and cardiac output (E) at six time points of the day (08:00, 12:00, 16:00, 20:00, 00:00, 04:00). The data are shown as the mean and standard error. ∗∗P < 0.01; ∗∗∗P < 0.001. Askna, average skin sympathetic nerve activity; MAP, mean arterial pressure; HR, heart rate; SVR, systemic vascular resistance; CO, cardiac output.

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  FIGURE 5. The proportion of PPT (A), PTO (B), CPT (C), and CTO (D) in subjects with or without significant periodic signal. Red shows the population with significant periodic signal, and blue shows the population without significant periodic signal. The change trend of the measured values with significant periodic signal is shown. Values are presented as mean ± standard error. PPT, pressure pain threshold; PTO, pressure pain tolerance; CPT, cold pain threshold; CTO, cold pain tolerance.

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  FIGURE 6. The proportion of skin sympathetic nerve voltage (A), mean arterial pressure (B), heart rate (C), peripheral vascular resistance (D), and cardiac output (E) in subjects with or without significant periodic signal. Red represents the population with significant periodic signal, and blue represents the population without significant periodic signal. The change trend of the measured values with significant periodic signal is shown. Values are presented as mean ± standard error. aSKNA, average skin sympathetic nerve activity; MAP, mean arterial pressure; HR, heart rate; SVR, systemic vascular resistance; CO, cardiac output.