Potential role of intermittent functioning of baroreflexes in the etiology of hypertension in spontaneously hypertensive rats
Feng Gu, E. Benjamin Randall, Steven Whitesall, Kimber Converso-Baran, Brian E. Carlson, Gregory D. Fink, Daniel E. Michele, Daniel A. Beard
Feng Gu, E. Benjamin Randall, Steven Whitesall, Kimber Converso-Baran, Brian E. Carlson, Gregory D. Fink, Daniel E. Michele, Daniel A. Beard
View: Text | PDF
Research Article Cardiology

Potential role of intermittent functioning of baroreflexes in the etiology of hypertension in spontaneously hypertensive rats

Abstract

The spontaneously hypertensive rat (SHR) is a genetic model of primary hypertension with an etiology that includes sympathetic overdrive. To elucidate the neurogenic mechanisms underlying the pathophysiology of this model, we analyzed the dynamic baroreflex response to spontaneous fluctuations in arterial pressure in conscious SHRs, as well as in the Wistar-Kyoto (WKY), the Dahl salt-sensitive, the Dahl salt-resistant, and the Sprague-Dawley rat. Observations revealed the existence of long intermittent periods (lasting up to several minutes) of engagement and disengagement of baroreflex control of heart rate. Analysis of these intermittent periods revealed a predictive relationship between increased mean arterial pressure and progressive baroreflex disengagement that was present in the SHR and WKY strains but absent in others. This relationship yielded the hypothesis that a lower proportion of engagement versus disengagement of the baroreflex in SHR compared with WKY contributes to the hypertension (or increased blood pressure) in SHR compared with WKY. Results of experiments using sinoaortic baroreceptor denervation were consistent with the hypothesis that dysfunction of the baroreflex contributes to the etiology of hypertension in the SHR. Thus, this study provides experimental evidence for the roles of the baroreflex in long-term arterial pressure regulation and in the etiology of primary hypertension in this animal model.

Authors

Feng Gu, E. Benjamin Randall, Steven Whitesall, Kimber Converso-Baran, Brian E. Carlson, Gregory D. Fink, Daniel E. Michele, Daniel A. Beard

×

Figure 4

The average level and lability of the MAP are lower during the on state compared with the off state in the SHR/WKY strains.

Options: View larger image (or click on image) Download as PowerPoint
The average level and lability of the MAP are lower during the on state ...
(A, C, and E) The gray solid lines represent the probability density distribution of the total MAP recording. The black solid lines represent probability density distributions of MAP during the on state, whereas the black dashed lines represent probability density distributions of MAP during the off states. The inset figures plot the MAP probability density functions normalized to have unit area for both on- and off-state distributions. The average level of MAP increases with age in the SHR and WKY, as shown in panels A and C. Furthermore, both the mean level and variability in MAP are lower during on states compared with during off states in the SHR and WKY (A and C) but not in the SD (E). The difference in average pressure increases with the progression of hypertension and aging. (B, D, and F) The mean values of the probability distributions of MAP for 8-, 10-, and 15-week SHR, WKY, and SD rats during baroreflex-on and -off states are plotted. Data are shown as mean. Unpaired 2-tailed Student’s t test, ****P < 0.0001.