Key result
Mean sympathetic nerve activity correlated better with low-frequency sympathetic nerve activity variability than with low-frequency blood pressure variability over a wide range in rats.
In nonanesthetized rats, the low-frequency component of blood pressure variability is a definitive index of mean sympathetic nerve activity only within a restricted range, whereas low-frequency sympathetic nerve activity variability correlates over a wider range.
LF BP variability should index sympathetic activity only narrowly in rat models; leaves open wider utility of LF SNA variability for translational research.
The low-frequency (0.2-0.8 Hz) component of blood pressure (BP) variability (LF(BP)) is used as an index of the low-frequency variability of sympathetic nerve activity (SNA) (LF(SNA)) in rats. It is unclear whether the LF(BP) can be used as an index of the mean SNA (mSNA). We investigated the correlation of the LF(BP) with different levels of the mSNA in this study to evaluate if it is a feasible tool for detecting differences in mSNA under physiological conditions. Correlation of the LF(SNA) with different mSNA levels was also investigated. The BP and renal SNA of rats were recorded in a nonanesthetized state. Values of the mSNA obtained from 531 recording epochs in six rats were graded into 30 levels with a bin resolution of 0.05 normalized units. A linear regression analysis showed that the correlation between the mSNA and LF(SNA) was higher than that between the mSNA and LF(BP). The mSNA was well correlated with the LF(SNA) over a wider mSNA range, while it was correlated with the LF(BP) only in a restricted range. These results demonstrated a restricted condition under which measuring the LF(BP) can be a definitive index of the mSNA, and further suggest the possibility of using the weighted LF(BP) as an index of the mSNA via intermediation by the LF(SNA) for a wider mSNA range.
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Tsai et al. (2009) studied this question. Low-frequency blood pressure variability (LF(BP)) vs. Low-frequency sympathetic nerve activity variability (LF(SNA)) was evaluated on Correlation with mean sympathetic nerve activity (mSNA). Mean sympathetic nerve activity correlated better with low-frequency sympathetic nerve activity variability than with low-frequency blood pressure variability over a wide range in rats.
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