Proceedings of The Physiological Society

University of Cambridge (2004) J Physiol 555P, PC11

Communications

Development of new software for the automation of analysis of cardiovascular autonomic function from chronic measurements of arterial pressure in conscious rats

Hidefumi Waki*, Kiyoaki Katahira†, Sergey Kasparov*, David Murphy‡ and Julian F.R. Paton*

* Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, †Experimental Animal Center, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan, ‡Henry Wellcome Laboratories for Integrative Neurosciences and Endocrinology, University of Bristol, Dorothy Hodgkin Building, Bristol BS1 3NY, UK


Radio-telemetry is an effective technique for recording pulsatile arterial pressure chronically in conscious, unrestrained rodents (Brockway et al. 1991; Waki et al. 2003). Mathematical analysis of this signal allows an evaluation of changes in vasomotor sympathetic tone, cardiac sympathetic and cardiac vagal tone (Pagani et al. 1986; Cerutti et al. 1991). Further, spontaneous alterations in blood pressure and corresponding changes in heart rate (HR) allow the spontaneous baroreflex cardiac gain (sBRG) to be measured (Oosting et al. 1997; Waki et al. 2003). To date this analysis has been highly time consuming requiring multiple software applications off-line. In this study, we introduce new software to automatically evaluate cardiovascular autonomic function on-line from an arterial pressure signal.

The software consists of 2 basic data elements: 1) acquisition and 2) analysis programs. In the data acquisition program, 4 channels of data can be recorded simultaneously at a sampling rate of up to 4 kHz per channel. The exact timing of data sampling, its duration and frequency of collection can be set for each channel. The data analysis program contains a fast Fourier transform function for power spectral analysis of HR variability as well as a program for measuring sBRG based on the time-series technique described previously (Waki et al. 2003). In telemetered rats (see Waki et al. 2003 for methods), we obtained chronic measurements of arterial pressure. To validate the new software, we measured changes in the high frequency (HF) power of the pulse interval (PI), which is an index of cardiac parasympathetic activity, before and after vagal blockade (atropine, 1 mg kg-1, I.V.). Low frequency (LF) /HF of PI, which is considered to reflect levels of cardiac sympathetic activity, was also calculated before and after cardiac sympathetic blockade (atenolol, 1 mg kg-1, I.V.). sBRG was measured before and after injection of these drugs.After vagal blockade, HR was significantly increased (324 ± 22 vs. 392 ± 10 bpm, mean ± S.D., P < 0.001, ANOVA, n = 4) while HF power of the PI was significantly decreased (28.5 ± 4.7 vs. 16.8 ± 2.3 msec2, P < 0.001, n = 4). Following subsequent sympathetic blockade, HR and LF/HF of PI was significantly decreased (HR, 392 ± 10 vs. 321 ± 12 bpm, P < 0.001; LF/HF of the PI, 0.37 ± 0.20 vs. 0.15 ± 0.02, P < 0.05, n = 4). The sBRG, was also decreased by 42 % after vagal blockade (0.69 ± 0.14 vs. 0.29 ± 0.05 msec mmHg-1, P < 0.001, n = 4) and decreased further after sympathetic blockade (0.29 ± 0.05 vs. 0.17 ± 0.04 msec mmHg-1, P = 0.08, n = 4). These findings in the sBRG were mirrored by measurements using conventional vasoactive drugs (before blockade, 0.63 msec mmHg-1; after vagal blockade, 0.27 msec mmHg-1; after vagal and sympathetic blockade, 0.12 msec mmHg-1).

These results suggest that our software adequately evaluates cardiovascular autonomic function from chronic measurements of arterial pressure that include HR variability and sBRG. We believe that it will be a powerful tool for analysis and quantification of long-term changes in cardiovascular autonomic function in conscious rodents. Additional functions to measure LF component of arterial pressure, which is considered to reflect changes in vasomotor sympathetic tone and respiratory rate, are currently under development.

JFRP was supported by the British Heart Foundation.

Where applicable, experiments conform with Society ethical requirements