Spectral analysis of heart rate and arterial pressure variability after nitric oxide synthase inhibition.

The experiments were performed on male, conscious Wistar rats. Femoral arterial pressure was registered by Statham GOULD P23 ID pressure transducer connected to MP 100WS BIOPAC work station after analog to digital conversion during 40 minutes long control period. Nitric oxide synthase inhibition was performed by injection of 100 microliters, 10 mg/kg b.w. N-omega-nitro-L-arginine methyl ester (L-NAME) in saline through femoral vein catheter. Twenty minutes later arterial pressure registration was started and was continued for 40 minutes. The pulse-by-pulse values of systolic, diastolic and mean arterial pressure as well as the pulse intervals were measured by peak and rate detectors of the AcqKnowledge 2.0 software. Row data were processed using a virtual instrument developed in our laboratory in the graphical programming environment Lab VIEW 3.1.1. L-NAME increased systolic, diastolic and mean arterial pressure by 16.6%, 25% and 35%, respectively. The PMF/PHF ratio in heart rate spectrum decreased, indicating an increased vagal effect on the heart. Nitric oxide synthase inhibition increased the low-frequency component of systolic arterial blood pressure variability by 39.5%. Nitric oxide is a physiological regulator of rapid fluctuations of arterial blood pressure.