December 26, 2014Open Access

Predominant Role of Neural Arc in Sympathetic Baroreflex Resetting of Spontaneously Hypertensive Rats

Q: What is the clinical evidence from this study?

Study design: Other. Population: Hypertension (n=48). Intervention: Spontaneous hypertension (SHR strain) vs. Normotensive Wistar Kyoto rats (WKY). Primary outcome: Midpoint pressure in the neural arc (CSP-SNA relationship) (p=<0.001).

Resultado clave

In spontaneously hypertensive rats, the neural arc of the carotid sinus baroreflex shifted to a higher midpoint pressure (157.9 vs 128.9 mmHg) and sympathetic nerve activity range, indicating its predominant role in baroreflex resetting.

PICO

Población

48 male adult spontaneously hypertensive and normotensive Wistar Kyoto rats were studied to analyze open-loop baroreflex equilibrium diagrams.

Exposición / comparador

Spontaneous hypertension (SHR strain) vs Normotensive Wistar Kyoto rats (WKY)

Resultado principal

Midpoint pressure in the neural arc (CSP-SNA relationship), p=<0.001

Resultado numérico

Tasa de eventos absoluta: 157.9% vs 128.9%

valor p: p=<0.001

Limitaciones

The carotid sinus baroreflex was examined under anesthetic conditions, so results are not directly extendable to the conscious state.
Only adult rats were used; studies on younger rats may be required to understand the development of hypertension.
Time windows for estimating peripheral arc characteristics differed between protocols, potentially affecting the contribution of pressure-diuresis.
The duration of baroreceptor pressure input (1 min per CSP level) might be too short to extrapolate to long-term therapeutic mechanisms.

Resumen

BACKGROUND: There is ongoing controversy over whether neural or peripheral factors are the predominant cause of hypertension. The closed-loop negative feedback operation of the arterial baroreflex hampers understanding of how arterial pressure (AP) is determined through the interaction between neural and peripheral factors. METHODS AND RESULTS: A novel analysis of an isolated open-loop baroreceptor preparation to examine sympathetic nervous activity (SNA) and AP responses to changes in carotid sinus pressure (CSP) in adult spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) was conducted. In the neural arc (CSP-SNA relationship), the midpoint pressure (128.9±3.8 vs. 157.9±8.1 mmHg, P<0.001) and the response range of SNA to CSP (90.5±3.7 vs. 115.4±7.6%/mmHg, P=0.011) were higher in SHR. In the peripheral arc (SNA-AP relationship), slope and intercept did not differ. A baroreflex equilibrium diagram was obtained by depicting neural and peripheral arcs in a pressure-SNA plane with rescaled SNA (% in WKY). The operating-point AP (111.3±4.4 vs. 145.9±5.2 mmHg, P<0.001) and SNA (90.8±3.2 vs. 125.1±6.9% in WKY, P<0.001) were shifted towards a higher level in SHR. CONCLUSIONS: The shift of the neural arc towards a higher SNA range indicated a predominant contribution to baroreflex resetting in SHR. Notwithstanding the resetting, the carotid sinus baroreflex in SHR preserved an ability to reduce AP if activated with a high enough pressure.

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Cite This Study

Sata et al. (Fri,) conducted a other in Hypertension (n=48). Spontaneous hypertension (SHR strain) vs. Normotensive Wistar Kyoto rats (WKY) was evaluated on Midpoint pressure in the neural arc (CSP-SNA relationship) (p=<0.001). In spontaneously hypertensive rats, the neural arc of the carotid sinus baroreflex shifted to a higher midpoint pressure (157.9 vs 128.9 mmHg) and sympathetic nerve activity range, indicating its predominant role in baroreflex resetting.

synapsesocial.com/papers/6a20dac76fcc58ca6c17fddf https://doi.org/https://doi.org/10.1253/circj.cj-14-1013

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