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Cross‐sample entropy statistic as a measure of complexity and regularity of renal sympathetic nerve activity in the rat
Author(s) -
Zhang Tao,
Yang Zhuo,
Coote John H.
Publication year - 2007
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2007.037150
Subject(s) - sample entropy , heart rate , baroreflex , reflex , medicine , kynurenic acid , heart rate variability , blood pressure , cardiology , anesthesia , antagonist , entropy (arrow of time) , receptor , physics , quantum mechanics
In this study, we employed both power spectral analysis and cross‐sample entropy measurement to assess the relationship between two time series, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA), during a mild haemorrhage in anaesthetized Wistar rats. Removal of 1 ml of venous blood decreased BP (by 7.1 ± 0.7 mmHg) and increased RSNA (by 25.9 ± 2.4%). During these changes, the power in the RSNA signal at heart rate frequency was reduced but coherence between the spectra at heart rate frequency in RSNA and ABP remained unchanged. Cross‐sample entropy was significantly increased (by 10%) by haemorrhage, revealing that there was greater asynchrony between ABP and the RSNA time series. Intrathecal administration of the glutamate receptor antagonist kynurenic acid (2 m m ) almost halved ( P < 0.01) the reflex increase in RSNA. Also during kynurenic acid block, haemorrhage failed to change total power, power at heart rate frequency, coherence at heart rate frequency, or the cross‐sample entropy measurements. We conclude that the increase in asynchrony between ABP and RSNA during the reflex increase in RSNA was a consequence of an increase in synaptic input to the spinal renal neurones. The data show that the cross‐sample entropy calculations can characterize the non‐linearities of neural mechanisms underlying cardiovascular control and have a potential to reveal how some aspects of homeostatic regulation of kidney function is achieved by the autonomic nervous system.