New insights in cardiovascular regulation under physiological and pathophysiologic...
| Grant number: | 12/03926-9 |
| Support type: | Regular Research Grants |
| Duration: | July 01, 2012 - June 30, 2014 |
| Field of knowledge: | Biological Sciences - Physiology |
| Principal Investigator: | Rubens Fazan Junior |
| Grantee: | Rubens Fazan Junior |
| Home Institution: | Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil |
Abstract
Heart failure (HF) is characteristically accompanied by a remarkable increase in the sympathetic activity. Several studies have shown that peripheral chemoreceptors (powerful sympathetic stimulators) have augmented sensitivity in both patients and experimental models of HF. The present study aims to evaluate the chemoreceptors influence on autonomic cardiovascular modulation and cardiac function in rats with HF induced by myocardial infarction (MI). Wistar rats will be implanted with a jugular catheter and telemetric recording probes, for arterial pressure (AP) and renal sympathetic nerve activity (RSNA). AP variations induced by vasoactive drugs will be used to evaluate the baroreflex sensitivity. Following, the chemoreflex sensitivity will be evaluated during acute hypoxia (7% O2). Two days after the baro- and chemoreflex evaluation, rats will receive atropine and propanolol (i.v.) to study cardiac autonomic tonus and intrinsic rate. Following, rats anesthetized with isoflurane will have the anterior descendent branch of the left carotid artery surgically ligated to induce a large MI. Control rats will have an isolated, but intact coronary. Rats with MI (and controls) will have the nurturing artery of the carotid body surgically ligated, for destruction of peripheral chemoreceptor by ischemia. Following the induction of MI, rats will be submitted to AP and RSNA telemetry recording periods, during 2 hours each 3 days for 4 weeks. These recordings will be used for AP, heart rate (HR) and RSNA evaluation during the HF development as well for studies of AP and HR variability at the time and frequency domine (spectral analysis). By the end of 4 weeks, new baro- and chemoreflex sensitivity tests, as well as autonomic tonus evaluation will be performed. Then, the rats will be anesthetized and submitted to the evaluation of cardiac function using a catheter specially designed for the ventricular pressure recording. By the end, the rat's heart will be removed and fixed for histological analysis and quantification of myocardial lesion. (AU)