Received January 24, 2007
Revised February 27, 2007
Accepted after revision April 10, 2007
Autonomic Neuroscience [200]
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Cross-Sample Entropy statistic as a measure of complexity and regularity of renal sympathetic nerve activity in the rat
Tao Zhang 1,
Zhuo Yang 1,
John H. Coote 2*
1 University of Nankai
2 University of Birmingham
* To whom correspondence should be addressed. E-mail: j.h.coote{at}bham.ac.uk.
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Abstract |
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Abstract
In this study we employed both power spectral analysis and cross-sample entropy measurement to assess the relationship between two time series, blood pressure (BP) and renal sympathetic nerve activity (RSNA), during a mild haemorrhage in anaesthetised Wistar rats. Removal of 1 ml of venous blood decreased BP (7.1±0.7mmHg) and increased RSNA (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 BP remained unchanged. Cross-sample entropy was significantly increased (10%) by haemorrhage revealing there was greater asynchrony between BP and the RSNA time series. Intrathecal administration of the glutamate receptor antagonist, kynurenic acid (2 mM) 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 decrease in asynchrony between BP 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.
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Key Words:
Autonomic nervous system, Haemorrhage, Sympathetic activity
