			Home About us Contact

Parasympathetic Nerve Stimulation (parasympathetic + nerve_stimulation)

Distribution by Scientific Domains

Life Sciences	33%

Selected Abstracts

Transvenous Parasympathetic Nerve Stimulation in the Inferior Vena Cava and Atrioventricular Conduction

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2000
PATRICK SCHAUERTE M.D.
Parasympathetic Stimulation in the Inferior Vena Cava. Introduction: In previous reports, we demonstrated a technique for parasympathetic nerve stimulation (PNS) within the superior vena cava, pulmonary artery, and coronary sinus to control rapid ventricular rates during atrial fibrillation (AF). In this report, we describe another vascular site, the inferior vena cava (IVC), at which negative dromotropic effects during AF could consistently he obtained. Moreover, stimulation at this site also induced dual AV nodal electrophysiology. Methods and Results: PNS was performed in ten dogs using rectangular stimuli (0.1 msec/20 Hz) delivered through a catheter with an expandable electrode basket at its tip. Within 3 minutes and without using fluoroscopy, the catheter was positioned at an effective PNS site in the IVC at the junction of the right atrium. AF was induced and maintained by rapid atrial pacing. During stepwise increase of the PNS voltage from 2 to 34 V, a graded response of ventricular rate slowing during AF was observed (266 ± 79 msec without PNS vs 1,539 ± 2,460 msec with PNS at 34 V; P = 0.005 by analysis of variance), which was abolished by atropine and blunted by hexamethonium. In three animals, PNS was performed during sinus rhythm. Dual AV nodal electrophysiology was present in 1 of 3 dogs in control, whereas with PNS, dual AV nodal electrophysiology was observed in all three dogs. PNS did not significantly change sinus rate or arterial blood pressure during ventricular pacing. Conclusion: Stable and consistent transvenous electrical stimulation of parasympathetic nerves innervating the AV node can be achieved in the IVC, a transvenous site that is rapidly and readily accessible. The proposed catheter approach for PNS can be used to control ventricular rate during AF in this animal model. [source]

Modulation of rabbit sinoatrial node activation sequence by acetylcholine and isoproterenol investigated with optical mapping technique

ACTA PHYSIOLOGICA, Issue 4 2009
D. V. Abramochkin
Abstract Aims:, Changes in the rabbit sinoatrial node (SAN) activation sequence with the cholinergic and adrenergic factors were studied. The correlation between the sinus rhythm rate and the leading pacemaker site shift was determined. The hypothesis concerning the cholinergic suppression of nodal cell excitability as one of the mechanisms associated with pacemaker shift was tested. Methods:, A high-resolution optical mapping technique was used to register beat-to-beat changes in the SAN activation pattern under the influence of the cholinergic and adrenergic factors. Results:, Acetylcholine (10 ,m) and strong intramural parasympathetic nerve stimulation caused a pacemaker shift as well as rhythmic slowing and the formation of an inexcitable region in the central part of SAN. In this region the generation of action potentials was suppressed. The slowing of the sinus rhythm (which exceeded 12.8 ± 3.1% of the rhythm control rate) always accompanied the pacemaker shift. Isoproterenol (10, 100 nm, 1 ,m) and sympathetic postganglionic nerve stimulation also evoked a pacemaker shift but without formation of an inexcitable zone. The acceleration of the sinus rhythm, which exceeded 10.5 ± 1.3% of the control rate of the rhythm, always accompanied the shift. Conclusions:, Both cholinergic and adrenergic factors cause pacemaker shifts in the rabbit SAN. While modest changes in the sinus rhythm do not coincide with the pacemaker shift, greater changes always accompany the shift and may be caused by it, according to one hypothesis. The formation of an inexcitable zone at the place where the leading pacemaker is situated is one of the mechanisms associated with pacemaker shift. [source]

Constitutive Secretion of Immunoglobulin a and Other Proteins into Lumina of Unstimulated Submandibular Glands in Anaesthetised Rats

EXPERIMENTAL PHYSIOLOGY, Issue 1 2003
G. B. Proctor
Salivary fluid secretion is dependent upon reflex stimuli mediated by autonomic nerves. In order to determine if immunoglobulin A (IgA) and salivary proteins are secreted in the absence of nerve stimulation, small volumes (< 2 µl) of saliva were consecutively collected from the submandibular duct of anaesthetised rats following rest pauses in order to sample the protein contents of the ductal system. Within the first 5 µl of such saliva collected by parasympathetic nerve stimulation, IgA and other salivary proteins reached peak concentrations that were over 20-fold greater than levels in parasympathetically stimulated saliva subsequently collected during a 5 min period of stimulation. Confocal microscopy of TRITC-labelled IgA added to live, acutely isolated submandibular acini indicated that it did not enter the lumina by paracellular leakage. IgG is thought to enter saliva by paracellular leakage but did not accumulate in luminal saliva in the present study. Electrophoresis suggested that the major proteins secreted in the absence of stimulation were the same as those present in subsequently stimulated saliva. It can be concluded that IgA and other major submandibular proteins are secreted into glandular lumina in the absence of nerve stimulation. The functional significance of such unstimulated protein secretion is at present unclear. [source]

Cellular Mechanisms of Vagally Mediated Atrial Tachyarrhythmia in Isolated Arterially Perfused Canine Right Atria

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2002
MASAMICHI HIROSE M.D.
Mechanism of Vagally Mediated AT.Introduction: Increased vagal tone significantly enhances susceptibility to atrial fibrillation (AF); however, the cellular mechanisms responsible for vagally mediated AF are not completely understood. Methods and Results: In 12 isolated arterially perfused canine right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions, during intracardiac parasympathetic nerve stimulation (IPS; 30 to 50 Hz) as a surrogate for vagal stimulation, and during acetylcholine (ACh) infusion (10 to 30 ,M). During steady-state pacing, action potential duration was shorter during ACh infusion (43 ± 9 msec) than during IPS (78 ± 7 msec, P < 0.001) or control (129 ± 5 msec, P < 0.001). In contrast, repolarization gradients were larger during IPS (13 ± 3 msec/mm) than during ACh infusion (3 ± 1 msec/mm, P < 0.01) or control (5 ± 1 msec/mm, P < 0.01). Transmural repolarization gradients were relatively small for each intervention tested. During ACh infusion, atrial tachyarrhythmia (AT) was easily initiated with a single premature stimulus and was associated with a focal pattern of activation (84%). AT also was easily initiated by a single premature stimulus during IPS; however, when repolarization gradients were large, patterns of conduction block and incomplete macroreentry were often observed (64%). Importantly, AT initiation during IPS was associated with focal activity (36%) when repolarization gradients were small. Conclusion: In contrast to ACh infusion, IPS generally increased dispersion of repolarization and was often associated with patterns of conduction block and incomplete macroreentry, similar to that associated with in vivo cervical vagal stimulation. However, IPS also was associated with a focal pattern of initiation that was independent of local repolarization gradients. These results suggest that during vagal stimulation, AT initiation does not always depend on repolarization gradients. [source]

Identification and Characterization of Atrioventricular Parasympathetic Innervation in Humans

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2002
KARA J. QUAN M.D.
AV Parasympathetic Innervation.Introduction: We hypothesized that in humans there is an epicardial fat pad from which parasympathetic ganglia supply the AV node. We also hypothesized that the parasympathetic nerves innervating the AV node also innervate the right atrium, and the greatest density of innervation is near the AV nodal fat pad. Methods and Results: An epicardial fat pad near the junction of the left atrium and right inferior pulmonary vein was identified during cardiac surgery in seven patients. A ring electrode was used to stimulate this fat pad intraoperatively during sinus rhythm to produce transient complete heart block. Subsequently, temporary epicardial wire electrodes were sutured in pairs on this epicardial fat pad, the high right atrium, and the right ventricle by direct visualization during coronary artery bypass surgery in seven patients. Experiments were performed in the electrophysiology laboratory 1 to 5 days after surgery. Programmed atrial stimulation was performed via an endocardial electrode catheter advanced to the right atrium. The catheter tip electrode was moved in 1-cm concentric zones around the epicardial wires by fluoroscopic guidance. Atrial refractoriness at each catheter site was determined in the presence and absence of parasympathetic nerve stimulation (via the epicardial wires). In all seven patients, an AV nodal fat pad was identified. Fat pad stimulation during and after surgery caused complete heart block but no change in sinus rate. Fat pad stimulation decreased the right atrial effective refractory period at 1 cm (280 ± 42 msec to 242 ± 39 msec) and 2 cm (235 ± 21 msec to 201 ± 11 msec) from the fat pad (P = 0.04, compared with baseline). No significant change in atrial refractoriness occurred at distances > 2 cm. The response to stimulation decreased as the distance from the fat pad increased. Conclusion: For the first time in humans, an epicardial fat pad was identified from which parasympathetic nerve fibers selectively innervate the AV node but not the sinoatrial node. Nerves in this fat pad also innervate the surrounding right atrium. [source]