Baroreflex sensitivity and susceptibility to systolic hypertension induced by DOCA-salt in the Sabra rat

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Abstract
Rats of the salt-resistant Sabra strain (SBN) have a more sensitive baroreflex control of heart rate than do normotensive hypertension-prone salt-sensitive (SBH) rats. To test the hypothesis that increased baroreflex sensitivity confers resistance to hypertension, aortic baroreceptor deafferentation (ABD) was performed in 7- to 10-wk-old SBN rats. This treatment reduced the slope of the mean arterial pressure-heart period (MAP-HP) relationship in response to infusions of increasing doses of phenylephrine in conscious rats, from 1.92 .+-. 0.21 to 0.66 .+-. 0.11 ms .cntdot. mm Hg-1 (P < 0.01). The latter value did not differ significantly from that of untreated SBH rats (0.56 .+-. 0.07 ms .cntdot. mm Hg-1). Treatment of uniphrectomized SBH, SBN-ABD, and sham-operated SBN rats for 3 wk with deoxycorticosterone acetate (DOCA; 25-mg pellet) and 0.9% NaCl + 0.4% KCl (to maintain normal serum K+ values), as drinking fluid, caused increases in systolic blood pressure from 126 .+-. 3 to 147 .+-. 5 mm Hg and 104 .+-. 6 to 130 .+-. 8 mm Hg in the former 2 groups, respectively, but no significant change (105 .+-. 3 to 110 .+-. 4 mm Hg) in SBN rats when measured by an indwelling arterial catheter in the tail artery. The slopes of the MAP-HP relationships of each of the above 3 groups of rats were not significantly altered by DOCA-salt treatment. A decrease in baroreflex control of the heart by ABD can render SBN rats sensitive to DOCA-salt-induced systolic hypertension.

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