Effects of nitric oxide synthesis inhibition on blood pressure and pulse interval spectral powers

Nitric oxidc is continuously released in the circulation where it can quickly modify the hemodynamic conditions and therefore affect blood pressure variability. Nevertheless the effect of nitric oxide on blood pressure variability has not been completely elucidated; moreover it remains unknown whether nitric oxide acts independently, in concert or in opposition with the autonomic nervous system. In order to answer these questions we studied the effects of nitric oxide synthesis inhibition in intact, sympathectomized (Sympx) and sino-aortic denervated (SAD) conscious WKY rats. Mean arterial pressure (MAP) and pulse interval (PI) were continuously recorded for 60 minutes both in absence and in presence of an 1-arginine analogue, 1-NMMA (iv bolus 100 mg.kg^-1, followed by a 1.5 mg.kg^-1.min^-1 infusion for 60 minutes). Data were analyzed by means of FFT power spectral analysis in the HF (3.0 to 0.8 Hz), MF (0.6 to 0.1 Hz), and LF (0.1 to 0.025 Hz) frequency bands. Sympathectomy moderately reduced MAP whereas SAD did not change it significantly. 1-NMMA increased MAP (intact: from 97.2±3.6 to 135.4±4.2 mmHg, p2 p2, p=ns). Concerning PI, 1-NMMA increased significantly LF power in sympathectomized rats and HF power in both intact and sympathectomized rats (all p