Relation of
Ventricular Fibrillation Threshold to Heart Rate
during Normal Ventilation and Hypoventilation in
Female Wistar Rats: A Chronophysiological Study
P. ŠVORC,
I. BRAČOKOVÁ , I. PODLUBNÝ1
Department
of Physiology, Medical Faculty, Šafárik
University and 1Technical University, Košice,
Slovak Republic
Received
September 16, 1999
Accepted March 6, 2000
Summary
The
aim of our study was to verify the relationship
between heart rate (HR) and ventricular
fibrillation threshold (VFT) during different
types of ventilation in female Wistar rats from
the circadian point of view. The ex-periments
were performed under pentobarbital anesthesia (40
mg/kg i.p., adaptation to a light-dark cycle
12:12 h, open chest experiments) and the obtained
results were averaged independently of the
seasons. The VFT measure-ments were performed
during normal ventilation (17 animals) and
hypoventilation (10 animals). The HR was
re-corded immediately before the rise of
ventricular arrhy-thmias. Results are expressed
as arithmetic means ± S.D. and differences are
considered significant when p<0.05. The basic pe-riodic characteristics were calculated using
single and population mean cosinor tests. The
results from our experiments have demonstrate
that 1) the VFT and HR respond identically to
hypoventilation by a decrease in the light and
also in the dark phases, and 2) hypoventilation
changes the 24-h course of the VFT without a
change in the 24-h rhythm of the HR. It is
concluded that the HR and VFT behave as two
independent functional systems without apparent
significant circadian dependence during both
types of ventilation.
Key words
Rat
· Circadian · Ventricular fibrillation
threshold · Heart rate · Hypoventi-la-tion
Reprint
requests
P. Švorc, Department of Physiology, Medical
Faculty, Šafárik University, Tr. SNP 1, 040 66
Košice, Slovak Republic.
e-mail: psvorc@central.medic.upjs.sk
