A central mechanism of acute baroreflex resetting in the conscious dog |
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Authors: | W Tan M J Panzenbeck M A Hajdu I H Zucker |
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Affiliation: | Department of Physiology and Biophysics, University of Nebraska College of Medicine, Omaha 68105. |
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Abstract: | The role of the central nervous system in the mechanism(s) involved in acute carotid baroreflex resetting was studied in six conscious, chronically instrumented, aortic-denervated dogs. Dogs were prepared for reversible vascular isolation of the carotid sinuses. Acute baroreflex resetting was induced by holding the left carotid sinus pressure (LCcsp) at a given value for 20 minutes using a pulsatile pressure control system while at the same time keeping the right carotid sinus pressure (RCSP) at a subthreshold level (approximately 40 mm Hg). At the end of the 20 minutes, the LCcsp) was reduced to approximately 20 mm Hg, and a baroreflex (RCSP-mean arterial pressure [MAP]) curve was generated on the right carotid sinus using static-step increases in carotid sinus pressure. At the control LCcsp of 100 mm Hg, the RCSP-MAP baroreflex had a threshold pressure (Pth) of 86.6 +/- 3.1 mm Hg and a set point pressure (Psp) of 104.7 +/- 2.5 mm Hg. Increasing LCcsp) to 140 mm Hg for 20 minutes caused these parameters for the right carotid baroreflex to increase. Pth and Psp increased by 18.4 +/- 4.0 and 14.2 +/- 3.0 mm Hg, respectively (p less than 0.05). The baroreflex curve, therefore, was shifted upward and to the right. Decreasing LCcsp to 60 mm Hg caused Pth and Psp to decrease by 24.7 +/- 5.0 and 18.1 +/- 2 mm Hg, respectively (p less than 0.05). The baroreflex curve was therefore shift downward and to the left. The percent of resetting of Pth and Psp was 46 +/- 9% and 36 +/- 8%, respectively, when LCcsp was 140 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS) |
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