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Interaction between direct sympathetic and vagus nerve stimulation on heart rate in the isolated rabbit heart
Author(s) -
Brack Kieran E.,
Coote John H.,
Ng G André
Publication year - 2004
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2003.002654
Subject(s) - chronotropic , stimulation , heart rate , vagus nerve , medicine , autonomic nervous system , vagus nerve stimulation , endocrinology , cardiology , blood pressure
The interaction between the effects of vagus nerve stimulation (VS) and sympathetic stimulation (SS) on intrinsic heart rate was studied in the novel innervated isolated rabbit heart preparation. The effects of background VS, at different frequencies – 2 Hz (low), 5 Hz (medium), 7 Hz (high) – on the chronotropic effects of different frequencies of SS – 2 Hz (low), 5 Hz (medium), 10 Hz (high) – were studied. The experiments were repeated in the reverse direction studying the effects of different levels of background SS on the chronotropic effects of different levels of VS. Background VS reduced the overall positive chronotropic effect of SS at steady state in a frequency dependent manner and the rate of increase in heart rate during low and medium SS (but not high SS) was slowed in the presence of background VS. These results suggest that pre‐ and postjunctional mechanisms may be involved in the sympatho–vagal interaction on heart rate. On the other hand, the chronotropic effect of VS was enhanced in the presence of background SS. Vagal stimulation appears to play a dominant role over sympathetic stimulation in chronotropic effects on the isolated heart. The innervated isolated heart preparation is a valuable model to study the complex mechanisms underlying the interaction between sympathetic and parasympathetic stimulation on cardiac function.