document: Time-varying properties of renal autoregulatory mechanisms In order to assess the possible time-varying properties of renal autoregulation , time-frequency and time-scaling methods were applied to renal blood flow under broad-band forced arterial blood pressure fluctuations and single-nephron renal blood flow with spontaneous oscillations obtained from normotensive -LRB- Sprague-Dawley , Wistar , and Long-Evans -RRB- rats , and spontaneously hypertensive rats . Time-frequency analyses of normotensive and hypertensive blood flow data obtained from either the whole kidney or the single-nephron show that indeed both the myogenic and tubuloglomerular feedback -LRB- TGF -RRB- mechanisms have time-varying characteristics . Furthermore , we utilized the Renyi entropy to measure the complexity of blood-flow dynamics in the time-frequency plane in an effort to discern differences between normotensive and hypertensive recordings . We found a clear difference in Renyi entropy between normotensive and hypertensive blood flow recordings at the whole kidney level for both forced -LRB- p < 0.037 -RRB- and spontaneous arterial pressure fluctuations -LRB- p < 0.033 -RRB- , and at the single-nephron level -LRB- p < 0.008 -RRB- . Especially at the single-nephron level , the mean Renyi entropy is significantly larger for hypertensive than normotensive rats , suggesting more complex dynamics in the hypertensive condition . To further evaluate whether or not the separation of dynamics between normotensive and hypertensive rats is found in the prescribed frequency ranges of the myogenic and TGF mechanisms , we employed multiresolution wavelet transform . Our analysis revealed that exclusively over scale ranges corresponding to the frequency intervals of the myogenic and TGF mechanisms , the widths of the blood flow wavelet coefficients fall into disjoint sets for normotensive and hypertensive rats . The separation of the scales at the myogenic and TGF frequency ranges is distinct and obtained with 100 % accuracy . However , this observation remains valid only for the whole kidney blood pressure/flow data . The results suggest that understanding of the time-varying properties of the two mechanisms is required for a complete description of renal autoregulation
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