Differential central integration of left versus right baroreceptor afferent input in spontaneously hypertensive rats

Figures

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  FIGURE 1. Representative raw data traces showing the effect of (a) left, (b) right, and (c) bilateral aortic depressor nerve stimulation (1, 2.5, 5, 10, 20, and 40 Hz delivered at 0.4 mA and 0.2 ms for 20 s) on cardiovascular parameters measured in one pentobarbital-anesthetized male spontaneously hypertensive rats. AP, arterial pressure; HR, heart rate; MBF, mesenteric blood flow; FBF, femoral blood flow.

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  FIGURE 2. Effects of left, right, and bilateral aortic depressor nerve stimulation (1–40 Hz, 0.4 mA, 0.2 ms, 20 s) on (a) maximal changes in mean arterial pressure (MAP), (b) immediacy of blood pressure responses as assessed by MAP gain, (c) sustainability of the blood pressure response as assessed by area under the MAP curve (AUC) and (d) maximal changes in heart rate (HR) in spontaneously hypertensive rats (n = 6–9). Results are expressed as mean ± SD. aP ≤ 0.05, left versus right ADN, bP ≤ 0.05, left versus bilateral and, and cP ≤ 0.05, right versus bilateral ADN analyzed by a two-way ANOVA followed by Bonferroni's post hoc. Note that left and bilateral stimulation of the ADN evoked greater changes (overall and/or at frequencies of 5–40 Hz) in MAP variables as compared with right-sided stimulation. With HR, bilateral stimulation evoked the largest bradycardia (both overall and at frequencies above 5 Hz).

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  FIGURE 3. Effects of left, right, and bilateral aortic depressor nerve stimulation (1–40 Hz, 0.4 mA, 0.2 ms, 20 s) on maximal changes in (a) mesenteric blood flow (MBF) and (b) mesenteric vascular resistance (MVR) in spontaneously hypertensive rats (n = 7–9). Results are expressed as mean ± SD. aP ≤ 0.05, left versus right, and and cP ≤ 0.05, right versus bilateral ADN analyzed by a two-way ANOVA followed by Bonferroni's post hoc. Note that left and bilateral stimulation evoked the greatest drops in MBF and MVR (both overall and variably at frequencies above 5 Hz).

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  FIGURE 4. Effects of left, right, and bilateral aortic depressor nerve stimulation (1–40 Hz, 0.4 mA, 0.2 ms, 20 s) on maximal changes in (a) femoral blood flow (FBF) and (b) femoral vascular resistance (FVR) in spontaneously hypertensive rats (n = 7–9). Results are expressed as mean ± SD. aP ≤ 0.05, left versus right ADN and cP ≤ 0.05, right versus bilateral ADN analyzed by a two-way ANOVA followed by Bonferroni's post hoc. Note that left and bilateral stimulation evoked the greatest changes in FBF and FVR (both overall and at frequencies above 5 Hz).

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  FIGURE 5. Effects of left (a), right (b), and bilateral (c) aortic depressor nerve (ADN) stimulation (1–40 Hz, 0.4 mA, 0.2 ms, 20 s) on differences in maximal changes in vascular resistance (VR) in spontaneously hypertensive rats (n = 7–9). Figure compares VR measured from the superior mesenteric artery, mesenteric vascular resistance (MVR) versus that measured from the femoral artery, femoral vascular resistance (FVR) under different stimulation conditions. Results are expressed as mean ± SD. aP ≤ 0.05, MVR versus FVR analyzed by a two-way ANOVA followed by Bonferroni's post hoc. Note that regardless of the neurostimulation side, stimulation of the ADN produced larger reductions in FVR compared with MVR (both overall and variably at frequencies between 1 and 40 Hz).