Effects of acute hypertonic saline infusion in heart rate variability in male Wistar rats

      The main objective of this study was to investigate the acute effect of hypertonic NaCl infusion on blood pressure (BP), heart rate (HR) and cardiovascular autonomic modulation by spectral analysis. Methods: The rats were divided in two groups: 1. Central infusion rats (CIR, n=5), a guide cannula was implanted into the lateral ventricle (LV) to infuse the solutions (0.9%, 1.8%, 3.6% and 7.2% NaCl). 2. Peripheral infusion rats (PIR, n=9) saline infusions were performed by right femoral vein. BP and HR were evaluated in freely moving and conscious animals through a cannula inserted in the right femoral artery, using data acquisition system (Windaq, 2000 Hz). HR variability was evaluated by spectral analysis using Cardio Series. Animals with histological confirmation of LV cannulation were considered in this study. Results: In CIR, we observed no differences in BP or HR after any saline infusion. However, the 0.9% and 1.8% saline infusions determined an increase in LF component of systolic BP. In PIR, we observed an increase in HR after 3.6% and 7.2% saline infusions, and a decrease in HR variability in time domain. The LF component of systolic BP increased after 0.9%, 1.8% and 7.2% saline infusion in CIR when compared to PIR. There was also an increase in both, LF and HF components in frequency domain of HR variability after 7.2% saline infusion in CIR vs. PIR. Conclusion: The solutions administrated in the PIR group altered HR and its modulations while the solutions infused in the LV altered only the BP sympathetic modulation. The volumes injected were too small (2 μL for LV rats and 0.1 mL for peripheral rats) to cause any change in HR or BP.
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