Cardiac Parasympathetic Nerve Research Articles

Effect of divalent cations on acetylcholine release from cardiac parasympathetic nerve endings.

The influence of several divalent cations on acetylcholine (ACh) release from vagus nerve terminals was studied in quiescent guinea-pig auricles. ACh release was induced by stimulus trains subthreshold for excitation of atrial cells. The ACh released evoked a hyperpolarization of the atrial cell membrane. Changes in ACh sensitivity of the atrial cell membrane were tested by application of ACh-containing solutions. ACh release increased with the external Ca concentration. External Sr maintained the ACh release in 'Ca-free' media. However, Sr ions were less effective than Ca ions. External Mg acted as a weak inhibitor of the stimulus evoked ACh release, whereas Co and Mn ions exerted a strong inhibition.

Physiologic behavior of the in situ papillary muscles.

SummaryDistention of the intact right ventricular papillary muscles induced both mechanical and electrophysiologic changes in the whole heart. Severe dysrhythmia accompanied tension exerted upon the right, but not upon the left ventricular chordae tendineae. The right ventricular papillary muscles contain numerous receptors, stimulation of which induces marked changes in afferent impulse traffic in the cardiac nerves. Local papillary muscle contractile force was initially depressed and then elevated while that of distant myocardial segments was augmented during local papillary muscle distention. These responses were shown to be influenced by both sympathetic and parasympathetic cardiac nerves. A physiologic cardio-cardiac neural control mechanism is proposed to account for these dynamic cardiac events.

Role of the nervous system in the arrhythmias produced by coronary occlusion in the cat

The importance of the nervous system in the arrhythmias generated by occlusion of the left coronary artery of the cat was investigated. This was carried out by (1) monitoring the spontaneous electrical activity in sympathetic and parasympathetic cardiac nerves and (2) determining the influence of ablation of the nervous system on time taken for death to occur and on incidence of ventricular fibrillation. It was found that coronary occlusion increased the spontaneous firing in cardiac-bound autonomic fibers and that the enhanced neural activity was correlated in time with electrocardiographic changes consisting of ventricular arrhythmias. Removal of the central nervous system and both vagi conferred protection against arrhythmogenesis. Animals with no neural input to the heart (as indicated by the nerve recordings) survived more than twice as long after coronary occlusion and showed a significant reduction in the incidence of ventricular fibrillation. These results suggest that the nervous system plays an important role in the generation of arrhythmias produced by coronary occlusion in the cat.

A comparative morphologic study of the cardiac innervation in domestic animals II. The feline

AbstractDetailed morphological studies of the cardiac innervation of the cat were reported. Sympathetic cardiac nerves arose from the thoracic, cervicothoracic, vertebral, and intermediate ganglia. Parasympathetic cardiac nerves arose from the vagi, both cranial and caudal to the origin of the recurrent laryngeal nerves, and from the right recurrent laryngeal nerve. Left cardiac nerves passed primarily to the caudal and right surfaces of the left chambers while right ones ramified on the right chambers and left portion of the left chambers. Left cardiac nerves are more prominent around the coronary sinus and atrioventricular node, while right ones contribute more to the area of the sinoatrial node. Both sympathetic and parasympathetic nerves were followed to each chamber. Interconnections through the cardiac plexus facilitated overlapping of nerve distributions.

Effect of stimulation of cardiac sympathetic nerves on vagus escape of the heart

1. The effect of stimulation of the sympathetic nerves against the background of stimulation of the vagus is determined by which cardiac sympathetic and parasympathetic nerves are stimulated simultaneously, and by the strength of this stimulation. 2. When automatism of the sino-atrial node is predominantly depressed during stimulation of the vagus (usually the right), a more rapid onset of vagus escape is observed during stimulation of sympathetic nerves that increase the automatism of the atrioventricular (AV) node or of the third-order pacemakers. If, on the other hand, during stimulation of the vagus (usually the left) automatism of the AV node is predominantly depressed, a more rapid onset of vagus escape takes place during stimulation of sympathetic nerves that increase the automatism of the sino-strial or of the third-order pacemakers. 3. Stimulation of sympathetic branches influencing predominantly the sino-atrial node, or stimulation of sympathetic branches influencing predominantly the AV node, differs in its effect depending on the degree to which the automatism of these nodes is depressed by vagal stimulation. If depression of automatism is slight, vagus escape develops more rapidly, but if automatism is strongly depressed, this effect is absent. 4. Stimulation of the augmentor nerves has no effect either on the duration of vagal cardiac arrest or on vagus escape.

Hypothalamic stimulation and the inhibition of the activity of cardiac sympathetic and parasympathetic nerves.

AbstractThe electrical activity from the left sympathetic and parasympathetic cardiac nerves was recorded simultaneously with the activity from bulbar neurones. Electrodes for stimulating or recording were placed stereotaxically in the posterior hypothalamus, in the medulla and in the sygmoid gyrus of a dog.During the hypothalamic stimulation the sympathetic discharge increased but it was strongly reduced immediately after the cessation of the stimuli. In all experiments the spontaneous sympathetic activity was invariably reduced after the hypothalamic stimulation. In most experiments the parasympathetic discharge was also reduced but in some cases the vagal activity was increased simultaneously with the reduction in sympathetic discharge.The reduction in both sympathetic and parasympathetic discharges appeared independently of the values in systemic blood pressure.Several experimental observations indicate that the reduction in the sympathetic activity can not be attributed to fatigue but rather to an ac...