Arterial baroreflex function diminishes with age, but whether cardiopulmonary vagal reflexes are similarly altered with physiological aging has not been fully elucidated. In this study, predominantly cardiac high pressure mechanoreceptor-activated (ramp baroreflex) and cardiopulmonary chemoreceptor-activated (von Bezold-Jarisch reflex) vagal reflexes in conscious, instrumented rats were impaire...

The purpose of this study was to examine the influence of age and moderate-intensity exercise training on heart rate variability (HRV), and to elucidate further the mechanism of training-induced bradycardia and cardioprotection. Electrocardiograms were recorded from 12 young (18-24 yrs) and 12 mature (29-43 yrs) individuals during supine rest and submaximal moderate exercise. Recordings were ob...

Vasovagal syncope is a complex interaction of neurologic and cardiovascular mechanisms resulting in cardiac inhibition by the parasympathetic nervous system via vagus nerve associated ganglionic plexi. Some types tachycardia may be induced bradycardia, LQT type 3 being most common example. In these patients, pacemaker sometimes indicated to avoid bradycardia trigger for tachycardia. Cardioneura...

In dogs anesthetized with intravenous chloralose, vasopressin was injected either intravenously or into the cerebral ventricles, and the cardiovascular effects were studied before and after stabilizing the arterial blood pressure, bilateral vagotomy, and transection of the cervical cord at the level of C2. Intravenous vasopressin caused a rise in arterial blood pressure and pronounced bradycard...

Clinical and electrophysiological studies of a 13-year-old boy with sinus bradycardia revealed sinus node dysfunction. Long-term follow-up data of members of his family indicated familial sinus node dysfucntion. Increased vagal tone was present in all patients. It is suggested that excessive vagal discharge for a pronlonged time may be the basic mechanism of sinus node dysfunction in these pati...

Intravenous B-type natriuretic peptide (BNP) enhances the bradycardia of reflexes from the heart, including the von Bezold-Jarisch reflex, but its site of action is unknown. The peptide is unlikely to penetrate the blood-brain barrier but could act on afferent or efferent reflex pathways. To investigate the latter, two types of experiment were performed on urethane-anesthetized (1.4 g/kg iv) ra...

Nitric oxide (NO) generated from neuronal nitric oxide synthase (NOS-1) in intrinsic cardiac ganglia has been implicated in parasympathetic-induced bradycardia. We provide direct evidence that NOS-1 acts in a site-specific manner to promote cardiac vagal neurotransmission and bradycardia. NOS-1 gene transfer to the guinea pig right atrium increased protein expression and NOS-1 immunolocalizatio...

Bradycardia is common in critical care units. It may be transient, asymptomatic and of little consequence, or life-threatening. Bradycardia may result from abnormalities of the sinus node, atrioventricular node, or the His-Purkinje system. It may also be precipitated by drug effects or enhanced vagal tone. Proper diagnosis is pivotal to determining prognosis and management. Temporary and perman...

We found that sinus bradycardia in members of a large family was associated with a mutation in the gene coding for the pacemaker HCN4 ion channel. Pacemaker channels of the sinoatrial node generate spontaneous activity and mediate cyclic AMP (cAMP)-dependent autonomic modulation of the heart rate. The mutation associated with bradycardia is located near the cAMP-binding site; functional analysi...

The cerebral ischemic response was elicited in anesthetized rabbits by briefly clamping both common carotid arteries after previously occluding the vertebral arteries. The primary cerebral ischemic response, elicited after elimination of baroreceptors, consisted of arterial hypertension, bradycardia, and apnea. The hypertension resulted from a sterotyped and differentiated pattern of vasoconstr...