Autonomic and ventilatory contributions to spontaneous short-term
heart rate and blood pressure fluctuations in conscious rats.
Perlini, Stefano, Francesco Giangregorio, Michel Coco, Alberto
Radaelli, Pier L. Sold[grave]a, Luciano Bernardi, Alberto U. Ferrari.
Centro Fisiologia Clinica ed Ipertensione, Universit[grave]a di
Milano; Divisione di Cardioriabilitazione, Ospedale di Seregno;
*Dipartimento di Medicina Interna, Clinica Medica 1,
Universit[grave]a di Pavia, Italy
APStracts 2:0277H, 1995.
The relative role of parasympathetic, sympathetic and ventilatory
influences in the genesis of blood pressure (BP) and RR interval (RR)
variability is controversial. In 13 freely-behaving WKY rats
instrumented with venous and arterial catheters and chest electrodes,
mean BP (MAP, mmHg), RR interval (msec) and respiratory fluctuations
were monitored for 90 min in the control condition and after i.v.
atropine (0.75 mg/kg) and/or propranolol (1mg/kg). Spectral power
(pw) in the 0.25-0.75 Hz (mid-frequency, MF) and the 0.75-3.0 Hz
(high frequency, HF, respiratory-synchronous) bands was computed in
sequences of 400 heart beats using a combined autoregressive
analysis. Atropine reduced, but did not abolish HF-RR interval pw
(from 1.73+/-0.50 to 0.39+/-0.27 msec2, p<0.01) and halved HF
-MAP pw (from 0.41+/-0.30 to 0.21+/-0.12 mmHg2, p<0.05), whereas
propranolol did not affect HF pw of either RR interval or MAP.
Propranolol also failed to significantly modify either MF-RR interval
pw (from 0.48+/-0.44 to 0.40+/-0.34 msec2, p=ns) or MF-MAP pw (from
0.54+/-0.39 to 0.42+/-0.20 mmHg2, p=ns) while atropine virtually
abolished MF-RR interval pw (from 0.48+/-0.44 to 0.01+/-0.01 msec2,
p<0.01) and also significantly reduced MF-MAP pw (from 0.54+/
-0.39 to 0.33+/-0.24 mmHg2, p<0.01). The effects of combined
blockade were similar to those of atropine alone. It is concluded
that in the unanesthetized rat efferent vagal influences are
responsible for a large fraction of HF-RR power, but a sizeable
amount of such fluctuations persists after atropine and has a
ventilatory rather than an efferent vagal origin. Vagal influences
also contribute to HF-MAP power. Vagal (but not sympathetic)
influences are important determinants of MF-RR fluctuations and also
contribute significantly to MF-MAP fluctuations.
Received 30 January 1995; accepted in final form 6 June 1995.
APS Manuscript Number H83-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.