Impairment of sympathetic baroreceptor reflexes in obese Zucker rats

Ann M. Schreihofer, Daniel A. Mandel , Susan C. Mobley , David W. Stepp American Journal of Physiology - Heart and Circulatory Physiology Published 1 October 2007 Vol. 293 no. H2543-H2549 DOI: 10.1152/ajpheart.01201.2006 In this article they looked at baroreceptor reflexes in obese and lean zucker rats that were 7 or 14 weeks old. They instrumented the animals so they could record arterial pressure (AP), splanchnic nerve activity (sSNA) and they also looked at heart rate (HR) changes. In the 7 week old rats they found that there was no difference between the obese and lean zucker rats in responses to phenylephrine and nitroprusside. However when they did sigmoidal analysis of the PE and SNP responses, they found that the baroreflex gain was significantly blunted. As for the 14 week old rats the obese zucker rats had blunted responses to nitroprusside and phenylephrine challenges when compared to the lean zucker rats. The also showed that the baseline weight and AP was significantly elevated in the 14 week old obese zucker rats when compared the lean zucker rats. As for the 7 week old rats the obese rats were significantly heavier compared to the lean rats. These data suggest that impaired baroreflex compensation occurs in adult rats after they become obese not in juvenile rats.-MD