Hemodynamic responses to acute aortic coarctation in conscious sinoaortic denervated rats

Abstract

The hemodynamic responses to acute (45 min) partial aortic constriction were studied in conscious intact (N = 7) or sinoaortic denervated (SAD) adult male Wistar rats (280-350 g, N = 7) implanted with carotid and femoral arterial catheters, a pneumatic cuff around the abdominal aorta and a pulsed Doppler flow probe to measure changes in aortic resistance. In addition, the hypertensive response and the reflex bradycardia elicited by total (N = 8) vs partial (N = 7) aortic constriction (monitored by maintenance of the pressure distal to the cuff at 50 mmHg) were compared in two other groups of intact rats. Intact rats presented a smaller hypertensive response (26 to 40% above basal level) to partial aortic constriction than SAD rats (38 to 58%). The calculated change in aortic resistance imposed by constriction of the aorta increased progressively only in intact rats, but was significantly smaller (193 to 306%) than that observed (501 to 591%) in SAD rats. Intact rats showed a significant bradycardia (23 to 26% change in basal heart rate) throughout coarctation, whereas the SAD rats did not (1 to 3%). Partial or total occlusion of the aorta induced similar hypertensive responses (37-38% vs 24-30% for total constriction) as well as reflex bradycardia (-15 to -17% vs -22 to -33%) despite a greater gradient in pressure (97-98 vs 129-140 mmHg) caused by total constriction. The present data indicate that the integrity of the baroreflex in intact rats can cause the hypertensive response to level off at a lower value than in SAD rats despite a progressive increase in aortic resistance. In addition, they also indicate that the degree of partial aortic constriction by maintenance of the pressure distal to the cuff at 50 mmHg already elicits a maximal stimulation of the arterial baroreflex.

Physiological Sympathetic Activation Reduces Systemic Inflammation: Role of Baroreflex and Chemoreflex

“…Regarding the other periods evaluated, no difference was observed in the mean arterial pressure among groups at each time frame evaluated ( Figures 2B–E ). Concerning the heart rate under basal conditions, the subjects with BARO-X exhibited higher levels of heart rate than intact—an outcome already described in the literature ( 42 , 43 )—and CHEMO-X animals ( Figure 2F ). Ninety min after LPS, the subjects with BARO-X still showed higher heart rate levels than intact rats ( Figure 2G ).…”

Anterior hypothalamic β‐adrenoceptors in chronic aortic‐coarctated hypertensive rats: An interaction with central angiotensin II receptors

“…14 In aortic-coarctated (ACo) rats, the hypertensive state is attributed mainly to activation of the renin-angiotensin system, the effects of vasopressin and homeostasis of sodium, [17][18][19][20] as well as regulatory mechanisms such as the cardiovascular baroreceptor reflex. 21,22 The maintenance of the early hypertensive stage in ACo animals involves hypothalamic ␤ 1 -adrenoceptors 23 and the hypothalamic renin-angiotensin system. 24 Taking into account that the hypothalamic abnormalities change with hypertensive stage, the aim of the present study was to investigate a possible alteration in the activity of anterior hypothalamic ␤ 1 -and ␤ 2 -adrenoceptors, as well as AngII receptors, on blood pressure regulation in ACo rats at a chronic stage of hypertension.…”