The parasympathetic nervous system innervates the heart through two cervical vagal branches. The right vagal branch mainly influences the heart rate by the modulation of the rhythmogenesis of the sinoatrial node. The left branch predominantly influences the conduction properties of the atrioventricular (AV) node. We investigated the effect of asynchronous stimulation by the vagal nerves on the ...

The vagal nerves modulate adrenergic effects on sinus cycle length, atrioventricular (AV) nodal conduction, and refractoriness of atria and ventricles. We tested whether varying levels of vagal-sympathetic input could yield the same spontaneous sinus cycle length but also alter effective refractory periods of the right atrium, right ventricle, and left ventricle and AV nodal conduction times. D...

Complex sympathovagal interactions govern heart rate (HR). Activation of the postjunctional beta-adrenergic receptors on the sinus nodal cells augments the HR response to vagal stimulation, whereas exogenous activation of the presynaptic alpha-adrenergic receptors on the vagal nerve terminals attenuates vagal control of HR. Whether the alpha-adrenergic mechanism associated with cardiac postgang...

BACKGROUND Although we have shown that in rabbits the direct (heart rate [HR]-independent) vagal effect on left ventricular end-systolic elastance (E(es)) was negligible under minimal sympathetic tone, how underlying sympathetic tone modulates the inotropic response to vagal stimulation remains unknown. METHODS AND RESULTS We used an isolated canine heart preparation with functioning autonomi...

Background Atrial electrical remodeling(AER) plays an important role in the pathogenesis and maintenance of atrial fibrillation. However, little is known about modulation of vagal activity to AER. This study aimed to investigate the relationship between vagal moduation and AER. Methods Twenty four adult mongrel dogs under general anesthesia were randomized into 3 groups. Sympathetic activity wa...

Concurrent stimulation of the parasympathetic and sympathetic branches of the autonomic nervous system causes a diminished sympathetic response at high levels of vagal activity. This "accentuated antagonism" has been demonstrated for cardiac chronotropic, inotropic, and dromotropic responses. The effect on conduction was demonstrated with tonic stimulation of the vagus nerve. However, normally ...

Using a new in vitro procedure of the isolated perfused rat pancreas with vagal innervation, electrical vagal stimulation produced an increase in both insulin and glucagon secretion in proportion to the pulse frequency, but an inhibition in somatostatin release. When atropine was infused, both insulin and glucagon responses to vagal stimulation were partially suppressed, whereas somatostatin re...

Efferent vagal stimulation in the anesthetized dog with constant ventricular rate caused either no change in coronary sinus outflow and cardiac work, or a decrease in coronary sinus outflow associated with a greater decrease in cardiac work. When the decreases were observed they could best be explained by a negative inotropic effect of vagal stimulation on ventricular muscle, rather than by a d...