Abstract 202: Temporal Evaluation of Baroreflex Dysfunction: Role in Target Organ Damage

Abstract

Introduction: Baroreceptors regulate moment-to-moment blood pressure (BP) variations, but their long-term effect on the cardiovascular system and target organ damage remains unclear. Purpose: to investigate the temporal mechanisms enrolled in the relationship between baroreceptor reflex dysfunction and end-organ damage in different pathophysiological conditions as hypertension, heart failure and myocardial infarction. Method: Male Wistar rats were divided into 5 groups: control (n = 9),SAD1(n=8,24h), SAD2(n=8,28 days), SAD3 (n=8, 90 days) and SAD4 (n=7, 6 months). Sinoaortic denervation (SAD) was used as a model of arterial baroreflex deficit. BP, HR were analysed using a data acquisition system (Codas, 2kHz). Cardiac output and tissues blood flow were evaluated using colored microspheres. Result: BP and the HR was incresed in SAD after 24h (C:106 ± 0.6 vs . SAD1: 142 ± 2 mmHg; C: 355 ± 7 vs . SAD1: 453 ± 10 bpm), but it were normalizaed in chronic SAD. Moreover, it was observed a gradual reduction over time in cardiac output (C: 111 ± 7, SAD1:81±5, SAD2:85 ± 6, SAD3:69±5 SAD4:35±2 mL/min) accompanied by an increase in total peripheral resistance (C:0.97±0.07, SAD1:1.74±0.05, SAD2:1.23±0.07, SAD3:1.60±0.09, SAD4:3.00±0.05 mL/min/mmHg) in SAD groups. Those alterations resulted in a decreased renal blood flow (C:3.47±0.21, SAD1:1.37±0.19, SAD2:1.49±0.18, SAD3:1.12±0.13, SAD4:0.42±0.16 mL/min/g) , cardiac blood flow (C:2.91±0.71, SAD1:2.07±0.19, SAD2:1.58±0.28, SAD3:0.92±0.13, SAD4:0.34±0.16 mL/min/g) and muscle blood flow (C:0.24±0.02, SAD1:0.08±0.005, SAD2:0.10±0.02, SAD3:0.05±0.01, SAD4:0.05±0.007 mL/min/g) in SAD groups. Conclusion: The acute total baroreflex dysfuntion incresed BP and HR and reduced blood flow and cardiac output, these changes are associated with the body’s attempt to maintain homeostasis. Howerer, the temporal evaluation showed a progressive reduction in CO and regional blood flow associated with an increase in RPT to maintain blood pressure levels. These adjustements may play an important role in target organ-damage in different pathological conditions, independently of BP levels.