Abstract
The aims of this study are to analyze arterial pressure variability (APV) and heart rate variavility (HRV) in conscious rats using power spectral techniques, and to examine the hemodynamic effects of nitric oxide (NO) and ATP-sensitive K+ (KATP) channels on sympathetic activity in arterial pressure regulation. Experiments were performed on male normotensive Whistar rats (n = 32), 10–13 wks of age. A polyethylene catheter for arterial pressure measurement was inserted from the right femoral artery into the terminal abdominal aorta under anesthesia. Another catheter for injection of drugs was inserted into the right external jugular vein. Three days post-operation, AP and HR were measured in the conscious resting state. Hexamethonium C6 (25 mg/kg), L-NAME (5 mg/kg), L-arginine (150–200 mg/kg), glibenclamide (3 mg/kg), cromakalim (0.067 mg/kg) and prazosin (200 μg/kg) were infused. The effects of the drugs on APV and HRV were examined using power spectral analysis with a sampling interval of 0.05 seconds. Findings indicate that: (1) sympathetic activity (< 0.6 Hz) in arterial pressure regulation was buffered by NO. NO-buffering capacity was modulated by activation of KATP channels, (2) very low oscillations (0.002–0.2 Hz) were mediated by sympathetic nerve activity, vasomotion, and neurohumoral factors, (3) low oscillations (0.2–0.6 Hz) were mediated by the baroreflex, and (4) high oscillations (0.6–2.5 Hz) were mediated vagally. We concluded that the NO-buffering effects on sympathetic activity may be backed up by activation of KATP channels. [Jpn J Physiol 55 Suppl:S86 (2005)]
