Spectral Analysis of Blood Pressure and Heart Rate Variability during Hemorrhage After Losartan Administration into the Lateral Ventricle

This study was aimed to elucidate the effect of intracerebroventricular losartan administration on arterial pressure regulation during hemorrhage in rats by power spectral analysis of blood pressure and heart rate variability. Nineteen male Sprague-Dawley rats weighing 240-300g were divided into losartan-administered (n=10 and control(n=9 groups. Hemorrhage was induced with a withdrawal pump from the fem- oral artery at 3ml/kg/min for 5min. Arterial pressure was measured with a pressure transducer connected to the contralateral femoral artery for 5 min before, during and after hemorrhage. The blood pressure signal digitized at 500 Hz through a data acquisition system was analyzed with fast Fourier transform algorithm to yield power spectra of systolic(SP and diastolic(DP blood pressure and instantaneous heart rate(HR. Powers of very low frequency(VLF, 0.02-0.26Hz, low frequency (LF, 0.26-0.75Hz and high frequency(HF, 0.75-5.00Hz band were obtained. Basal systolic and diastolic blood pressure was 149±9 and 99±2mmHg, respectively, and was not changed by hemorrhage in control rats. Basal blood pressure in losartan group was 143±9 and 97± 6mmHg and was significantly lowered to 116±13 and 77±9mmHg, respectively. HR was signific- antly increased during and after hemorrhage in both groups. Total power of SP variability in losartan group was 13.9±3.2mmHg 2 before hemorrhage and was significantly increased to 66.6±25.3mmHg 2 during hemorrhage. VLF, LF and HF powers of SP variability were 7.3±2.0, 3.8±1.1 and 2.8±0.7 mmHg 2 , respectively, in losartan group and 5.5±1.4, 3.7±1.5 and 2.8±0.8mmHg 2 in control rats. VLF and HF powers of SP were increased to 33.0±15.2 and 20.3±6.4mmHg 2 in losartan group, and VLF power was increased to 7.9±1.5mmHg 2 in control group. VLF power of DP variability increased from 3.3±0.9 before hemorrhage to 5.9±1.0mmHg 2 during hemorrhage in control group. Powers of * 본 연구는 1995년도 한국과학재단 핵심전문연구비의 지원으로 이루어졌음.