Predominant role of neural arc in sympathetic baroreflex resetting of spontaneously hypertensive rats.
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.
Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center; Department of Artificial Organ Medicine, Faculty of Medicine, Osaka University Graduate School of Medicine, Suita, Japan. yusukesa@ri.ncvc.go.jp
Yusuke
Y
Sata
Toru
T
Kawada
Shuji
S
Shimizu
Atsunori
A
Kamiya
Tsuyoshi
T
Akiyama
Masaru
M
Sugimachi
D000818:Animals; D017704:Baroreflex; D006973:Hypertension / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D011311:Pressoreceptors / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY