P3.16 EFFECTS OF SYMPATHETIC BLOCKADE ON PRESSURE DEPENDENT ABDOMINAL AORTIC STIFFNESS IN THE SPONTANEOUSLY HYPERTENSIVE RAT
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Background: Increased sympathetic nerve activity (SNA) is associated with development of hypertension in spontaneously hypertensive rats (SHR). Elevated SNA increases arteriolar smooth muscle tone affecting peripheral resistance, however, the effect on large arteries is not well established. This study aimed to assesses the effect of SNA on aortic stiffness in SHR using sympathetic blockade at different values of mean arterial pressure (MAP).
Methods: SHR of 10–15 weeks (n=15) were anaesthetized (urethane 1.3g/kg/ml) and ventilated. Aortic blood pressure and pulse wave velocity (PWV) were measured by two high fidelity catheter-tip pressure transducers in the abdominal aorta via the carotid and femoral arteries. Aortic diameters were measured using ultrasound (6.2 MHz) with vessel tracking software (ArtLab, Esaote). Aortic compliance was calculated from diameter and pressure signals. Measurements were taken at low (70 mmHg), intermediate (140 mmHg) and high (170 mmHg) values of basal MAP and following sympathetic blockade with hexamathonium (i.v 20mg/kg). Arterial pressure was varied by bolus injection of phenylephrine (i.v 30μg/kg).
Results: Increase in MAP was associated with increase in arterial stiffness indices. Following sympathetic blockade, there was a trend for reduction in compliance associated with a significant increase in pulse pressure at low MAP. There was no significant difference in parameters at other values of MAP.
| MAP (mmHg) | Parameter | Control | Hex. | Difference % | P-value |
|---|---|---|---|---|---|
| 70 | C (ml/mmHg) | 7.1 ± 1.6 | 6.2 ± 1.7 | 14.5 | 0.07 |
| PP (mmHg) | 38.1 ± 5.6 | 42.3 ± 7.6 | −9.9 | 0.03 * | |
| PWV (m/s) | 2.9 ± 1.2 | 2.8 ± 1.1 | 3.6 | 0.14 | |
| 140 | C (ml/mmHg) | 3.4 ± 1.0 | 3.3 ± 0.7 | 3.0 | 0.55 |
| PP (mmHg) | 53.8 ± 4.8 | 54.8 ± 6.5 | −1.8 | 0.43 | |
| PWV (m/s) | 5.3 ± 1.0 | 5.5 ± 1.0 | −3.6 | 0.08 | |
| 170 | C (ml/mmHg) | 2.0 ± 0.5 | 2.2 ± 0.4 | −9.1 | 0.16 |
| PP (mmHg) | 72.4±10.9 | 71.7±11.5 | 1.0 | 0.88 | |
| PWV (m/s) | 6.5 ± 1.3 | 7.0 ± 1.5 | −7.14 | 0.13 |
C: compliance; PP: pulse pressure; PWV: pulse wave velocity; Hex: hexamathomium;
Conclusions: These data suggest that sympathetic blockade can potentiate a stiffening effect in the abdominal aorta at low MAP in the SHR. This may be due to reduction of smooth muscle tone transferring the load from elastin to collagen in the vessel wall.
Cite this article
TY - JOUR AU - G. Lindesay AU - M. Butlin AU - A. Avolio PY - 2012 DA - 2012/11/17 TI - P3.16 EFFECTS OF SYMPATHETIC BLOCKADE ON PRESSURE DEPENDENT ABDOMINAL AORTIC STIFFNESS IN THE SPONTANEOUSLY HYPERTENSIVE RAT JO - Artery Research SP - 181 EP - 181 VL - 6 IS - 4 SN - 1876-4401 UR - https://doi.org/10.1016/j.artres.2012.09.142 DO - 10.1016/j.artres.2012.09.142 ID - Lindesay2012 ER -