Perfusion of Brain Preautonomic Areas in Hypertension: Compensatory Absence of Capillary Rarefaction and Protective Effects of Exercise Training

Figures

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  Figure 1. Effects of hypertension and exercise training on capillary volume within paraventricular nucleus of hypothalamus (PVN) nuclei. (A) Representative immunofluorescent staining of intravascular fluorescein isothiocyanate (FITC)-dextran taken from transverse sections of medial PVN of sedentary (S) and trained (T), Wistar Kyoto (WKY), and spontaneously hypertensive rat (SHR); scale bars: 50 μm; 3V, third ventricle. Enlarged drawings below are examples of the tridimensional reconstruction of the capillary profile (15 μm depth) within the ventromedial PVN (PVNvm) in one SHR-S (left) and other SHR-T (right). Bar graphs show the effects of hypertension and training on microcirculatory profile in the PVNvm (B), magnocellular [PVNmg, (C)], and posterior [PVNpost, (D)] nuclei of SHR and WKY submitted to S and T protocols. Measurements were made in 12–20 brain slices/rat, four rats/group. Group, condition, and interaction effects are presented in a Supplementary Material. Significances (p < 0.05) are: *vs. WKY, †vs. S.

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  Figure 2. Effects of hypertension and exercise training on capillary volume within nucleus of the solitary tract (NTS) nuclei. (A) Representative immunofluorescent staining of intravascular FITC-dextran taken from NTS transverse sections of sedentary (S) and trained (T), WKY, and SHR; scale bars: 50 μm; cc, central canal. Bar graphs show the effects of hypertension and training on microcirculatory profile in the commissural [NTScomm, (B)], intermediate [NTSint, (C)], and medial [NTSmed, (D)] nuclei of SHR and WKY submitted to S and T protocols. Measurements were made in 12–20 brain slices/rat, 3–5 rats/group. Group, condition, and interaction effects are presented in a Supplementary Material. Significances (p < 0.05) are: *vs. WKY, †vs. S.

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  Figure 3. Effects of hypertension and exercise training on remodeling of brain arteries. Photomicrographs (A) taken from the basilar artery of sedentary (S) and trained (T), WKY and SHR; H&E staining, ×200 magnification. Bar graphs show the effects of hypertension and training on wall/lumen ratio of the basilar [BA, (B)], posterior [PCA, (C)], and middle [MCA, (D)] cerebral arteries of WKY and SHR groups submitted to S and T protocols. Measurements were made in 12–15 slices/rat, 3–4 rats/group. Group, condition, and interaction effects are presented in a Supplementary Material. Significances (p < 0.05) are *vs. WKY; †vs. S.

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  Figure 4. Effects of hypertension and exercise training on carotid blood flow (CBF) and hemodynamic parameters of sedentary (S) and trained (T), WKY, and SHR. (A) Comparison of simultaneous recordings of pulsatile (PAP) and mean arterial pressure (MAP), heart rate (HR), and pulsatile CBF at rest in one WKY-S (left) and one SHR-S (right). (B) Quantitative measurements of systolic CBF at basal condition. (C) Changes from baseline systolic CBF observed during a mild acute bout of exercise on the treadmill (Delta CBF). n = 5–7 rats/group. Group, condition, and interaction effects are presented in a Supplementary Material. Significances (p < 0.05) are: *vs. WKY, †vs. S.

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  Figure 5. Schematic representation of the main findings of the study. (A) Scheme depicting the remodeling of arteries and capillary network changes induced by hypertension and exercise training in sedentary (S) and trained (T), WKY, and SHR. Mean values of MAP and CBF (at rest and exercise) for each experimental situation were presented. Graphs represent the correlations between wall/lumen ratio of cerebral arteries and MAP (B) and between capillary volume within preautonomic areas and CBF (C) in sedentary and trained normotensive and hypertensive rats. For these plots, the values of the 3 arteries and of PVN and NTS were pooled together. Wall/lumen ratio × MAP: Y = 172x + 58, r = 0.812, p < 0.001; Capillary Volume × CBF: Y = −0.043x + 21, r = −0.654, p = 0.006. *denotes a significant correlation.