Document Detail

Baroreflex and somato-reflex control of blood pressure, heart rate, and renal sympathetic nerve activity in the obese Zucker rat.
MedLine Citation:
PMID:  21527543     Owner:  NLM     Status:  Publisher    
It has been reported that the baroreflex control of heart rate (HR) and sympathetic nerve activity (SNA) is attenuated in obese Zucker rats (OZR) compared to age matched lean (LZR) animals. However, what is not known is the extent to which the baroreflex control of mean arterial blood pressure (MAP) is altered in the OZR. In addition, it is not known whether the interactions of other sensory nerve input on autonomic control is altered in the OZR compared to the LZR. The aim of this study was to determine the baroreflex control of MAP, HR and renal SNA (RSNA) in the OZR and LZR using an open-loop baroreflex approach. In addition, the effect of brachial nerve stimulation (BNS) on the baroreflex control was determined in these animals. Age matched, male LZR and OZR were anaesthetised, and the carotid baroreceptors were vascularly isolated, bilaterally. The carotid sinus pressure was increased in 20 mmHg steps from 60 to 180 mmHg using an oscillating pressure stimulus. Baroreflex function curves were constructed using a 4-parameter logistic equation and gain calculated from the 1st derivative, which gave a measure of baroreceptor sensitivity, before and during BNS. The range over which the baroreflex could change MAP (28 ± 6 vs. 87 ± 5 mmHg, mean ± sem), HR (17 ± 4 vs. 62 ± 11 beat min-1), and normalised RSNA (NormNA) (22 ± 4 vs. 76 ± 11%) were significantly decreased in the OZR compared to LZR. Similarly the maximum gain (Gmax) was lower in the OZR: MAP -0.88 ± 0.22 vs -2.26 ± 0.17; HR -0.42 ± 0.18 ± -1.44 ± 0.22 beats mmHg-1; NormNA -0.54 ± 0.14 vs. -1.65 ± 0.30% mmHg-1. There was no difference in the mid point of the baroreflex curves for each variable between OZR and LZR. However, the minimum values obtained when the baroreceptors were maximally loaded were higher in the OZR, (MAP 68 ± 5 vs. 53 ± 4 mmHg; HR 455 ± 7 vs. 390 ± 13 beat min-1; NormNA -19 ± 4 vs. -48 ± 8%). BNS in the LZR resulted in an upward and rightward resetting of the baroreflex control of MAP and RSNA, and abolished baroreflex control of HR. The baroreflex control of RSNA, in the OZR during BNS, was further attenuated and reset upwards and to the right, while the HR response was abolished. With respect to MAP the baroreflex curve resets upwards and to the right to a point comparable with the LZR during BNS. These data show that there is an attenuated baroreflex control in the OZR and that the ability to reset to higher arterial pressure during somatic afferent nerve stimulation is similar to that in a LZR.
Gerard Davis
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-4-28
Journal Detail:
Title:  Experimental physiology     Volume:  -     ISSN:  1469-445X     ISO Abbreviation:  -     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-4-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
University of Otago.
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