Effect of
Autonomic Blockers on Heart Period Variability in
Calves: Evaluation of the Sympatho-Vagal Balance
G.
DESPRÉS, I. VEISSIER, A. BOISSY
Adaptation et Comportements Sociaux, URH, Centre
INRA de Clermont-Theix, 63122, Saint
Genes-Champanelle, France
Received June 26, 2001
Accepted November 1, 2002
Summary
This study was designed to validate the
measures of heart period variability for
assessing of autonomic nervous system control in
calves. Eight calves received an injection of
either 0.5 mg/kg atenolol (sympathetic tone
blockade), 0.2 mg/kg atropine sulfate
(parasympathetic tone blockade), 0.5 mg/kg
atenolol + 0.2 mg/kg atropine sulfate (double
autonomic blockade) or saline. In the
time-domain, we calculated the mean instantaneous
heart rate (HR), mean of RR intervals (MeanRR),
standard deviation of RR intervals (SDRR) and
that of the difference between adjacent intervals
(RMSSD). In the frequency-domain, the power of
the spectral band 0-1 Hz (TPW), the power of the
0-0.15 Hz band (LF), that of the 0.15-1 Hz band
(HF), and the LF/HF ratio were considered. The
net vago-sympathetic effect (VSE) was calculated
as the ratio of MeanRR in a defined situation to
MeanRR during the double blockade. Atenolol
injection had no effect on cardiac activity,
whereas atropine induced large modifications
which were moderated when atenolol was
administered at the same time. VSE, HR, MeanRR
and RMSSD were found to be valid indicators of
the parasympathetic tone of calves because of
large variations due to the drug and low
individual variations. No measure reflected the
sympathetic tone.
Key
words
Autonomic
nervous system · Heart period · Cholinergic antagonists · Adrenergic antagonists · Calves
Reprint
requests
Gérard Després, ACS, URH, Centre INRA de
Clermont-Theix, 63122, Saint Genes-Champanelle,
France.
E-mail: depres@clermont.inra.fr
|