Transfer function analysis of ventilatory influence on systemic
arterial pressure in the rat.
Kuo, Terry B. J., Cheryl C. H. Yang, and Samuel H. H. Chan.
Institute of Pharmacology and Center for Neuroscience, National
Yang-Ming University, Taipei 11221, Taiwan, Republic of China
APStracts 3:0192H, 1996.
We evaluated the hypothesis that fluctuations in systemic arterial
pressure (SAP) are under the influence of the respiratory pumping
mechanism, subjected to a modulatory action by the autonomic nervous
system that is exerted pri marily on the heart. Computer-generated
broad-band mechanical ventila tion (0-3 Hz) was applied to Sprague
-Dawley rats that were anesthetized with ketamine and paralyzed with
pancuronium. We observed excellent coherence between lung volume and
SAP signals at ventilatory rates between 0.5 and 2.5 Hz, which was
unaffected by phentolamine, propra nolol, atropine, bilateral
vagotomy or ventilatory stroke volume at 2-4 ml. Whereas bilateral
vagotomy exerted no discernible effect, propranolol elici ted a
significant, frequency-dependent (0.5-1.5 Hz) reduction in the
magnitude of both lung volume-SAP and lung volume-pulse pressure
transfer functions. There was also a shift towards 0 degrees for the
phase of lung volume-SAP transfer function over the same frequency
range. We conclude that the high-frequency component (0.8-2.4 Hz) of
SAP spec trum may be generated by the respiratory pumping mechanism.
However, the lower frequency end of this mechanical influence is
subjected to addi tional amplification by the autonomic nervous
system, in which [beta]-adrenergic system played a major role via its
influence on the heart.
Received 21 December 1995; accepted in final form 18 April 1996.
APS Manuscript Number H1189-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96