Modulation of vasomotive activity in rabbit external ophthalmic artery by neuropeptides.

Purpose. To investigate the vasomotive activity upon the external ophthalmic artery of vasointestinal peptide (VIP) and neuropeptide Y (NPY) using a previously developed model. Methods.

Effects of vagal stimulation on induction and termination of atrial fibrillation in an in vivo rabbit heart model.

Introduction: Vagal activity is thought to influence atrial electrophysiological properties and play a role in the initiation and maintenance of atrial fibrillation (AF). In this study, we assessed the effects of acute vagal stimulation (vagus_stim) on atrial conduction times, atrial and pulmonary vein (PV) refractoriness, and vulnerability to induction of AF in the rabbit heart with intact autonomic innervation.

Methods: An open-chest epicardial approach was performed in 11 rabbits (New Zealand; 3.

Effects of acute autonomic modulation on atrial conduction delay and local electrograms duration in paroxysmal atrial fibrillation.

Unlabelled: Slowed atrial conduction may contribute to reentry circuits and vulnerability for atrial fibrillation (AF). The autonomic nervous system (ANS) has modulating effects on electrophysiological properties. However, complex interactions of the ANS with the arrhythmogenic substrate make it difficult to understand the mechanisms underlying induction and maintenance of AF.

Amlodipine effects on vasomotion in rabbit external ophthalmic artery.

Background: In order to understand the role of ocular blood flow in normal and pathological conditions, knowledge of the pharmacological control mechanisms involved in the ocular vascular bed is essential. The present study was designed to investigate the reactivity of the rabbit external ophthalmic artery and its collaterals to amlodipine, in order to answer two questions: (1) What are amlodipine effects upon perfusion pressure and spontaneous oscillations in the in situ perfused rabbit eyes? (2) Can intraarterial amlodipine counteract ET-1 induced vasoconstriction?

Methods: Rabbit external ophthalmic arteries (n = 12) in a head-mounted preparation were cannulated and perfused with warmed tyrode. Vasomotor response curves to intraarterial injections of amlodipine 3 mg/ml followed by phenylephrine 250 microg (group A, n = 6) and to amlodipine 3 mg/ml after an intraarterial injection of endothelin-1 (ET-1) 27 microg/ml (group B, n = 6) were obtained.

Effects of stimulation and blockade of the autonomic nervous system on atrial refractoriness in patients with lone paroxysmal atrial fibrillation.

Unlabelled: Heterogeneous shortening of the atrial effective refractory period (AERP) and increased dispersion of refractoriness (disp_A) predispose to recurrent episodes of atrial fibrillation (AF).

Aim: To evaluate the effects of stimulation and blockade of the autonomic nervous system (ANS) on atrial refractoriness in patients with > or = 1 year clinical history of lone paroxysmal AF (PAF).

Methods: Ten patients (6 men, aged 55 +/- 14 years) underwent electrophysiological study while off medication.

Endothelin-1 effects on spontaneous oscillations in choroidal arterioles.

Purpose: This study characterizes the effects of endothelin-1 (ET-1) on the perfusion pressure of the choroidal vasculature using in situ perfused isolated rabbit eyes.

Methods: Rabbit external ophthalmic arteries (n = 12) in a head-mounted preparation were cannulated and perfused with warmed tyrode. The three-way polypropylene catheter was further connected to a pressure transducer and the effect of intraluminal pressure as a measure of total vascular resistance was assessed.

Alterations in autonomic response head-up tilt testing in paroxysmal atrial fibrillation patients: a wavelet analysis.

Unlabelled: The autonomic nervous system (ANS) is known to be an important modulator in the pathogenesis of paroxysmal atrial fibrillation (PAF). Changes in ANS control of heart rate variability (HRV) occur during orthostatism to maintain cardiovascular homeostasis. Wavelet transform has emerged as a useful tool that provides time-frequency decomposition of the signal under investigation, enabling intermittent components of transient phenomena to be analyzed.

Effects of endoscopic thoracic sympathectomy for primary hyperhidrosis on cardiac autonomic nervous activity.

Objective: Endoscopic thoracic sympathectomy is performed to treat primary hyperhidrosis. The second and third sympathetic thoracic ganglia excised also innervate the heart. Some studies have shown decreased heart rate but have not been conclusive regarding other cardiac effects of sympathectomy.

False positive responses to head-up tilt testing in elderly patients with paroxysmal atrial fibrillation.

Unlabelled: The autonomic nervous system (ANS) plays a role as a modulator in the pathogenesis of paroxysmal atrial fibrillation (PAF). The clinical pattern of vagally mediated PAF has been observed mainly in young patients. Neurocardiogenic responses during orthostatic stress are related to autonomic reflexes in which the vagal influence predominates.

Intrinsic vasomotricity and adrenergic effects in a model of isolated rabbit eye.

Purpose: We aimed to investigate the responsiveness of the ocular arteries to adrenergic drugs in a model of perfused isolated rabbit eye.

Methods: Rabbit external ophthalmic arteries (n = 15) in a head-mounted preparation were cannulated and the retinal and uveal vasculature perfused at a constant flow with warmed tyrode. The three-way polypropylene catheter was further connected to a pressure transducer and intraluminal pressure was taken as a measure of vascular resistance.

Inducibility of atrial fibrillation during electrophysiologic evaluation is associated with increased dispersion of atrial refractoriness.

Unlabelled: The impact of atrial dispersion of refractoriness (Disp_A) in the inducibility and maintenance of atrial fibrillation (AF) has not been fully resolved.

Aim: To study the Disp_A and the vulnerability (A_Vuln) for the induction of self-limited (<60 s) and sustained episodes of AF.

Methods And Results: Forty-seven patients with paroxysmal AF (PAF): 29 patients without structural heart disease and 18 with hypertensive heart disease.

The Valsalva maneuver revisited by wavelets.

The Valsalva maneuver is an autonomic test that evokes short sharp cardiovascular fluctuations mediated by the autonomic nervous system. Numerous spectral analysis methods have been proposed to analyze biological signals. When applied to heart rate (HR) variability, two major bands related to autonomic influence have been defined: LF (mainly sympathetic) and HF (parasympathetic).

Cerebellar haemorrhage as a cause of neurogenic pulmonary edema - case report.

The neurogenic pulmonary edema is a rare clinical situation caused by an imbalance characterized by an excessive sympathetic outflow. It is observed mostly in young patients, is associated with brain or spinal cord haemorrhage, trauma, tumours or infections and is usually fatal. A case of neurogenic pulmonary edema in a 27-year-old woman is presented, caused by a cerebellar haemorrhage due to a vermian and paravermian arteriovenous malformation rupture.

Effect of stimulation of anterior hypothalamic area on urinary bladder function of the anesthetized rat.

The hypothalamus is a key area for the integration of the autonomic features of affective behavior. Hypothalamic defence area (HDA) stimulation evokes major cardiorespiratory changes as well as modifications of general autonomic activity both in the anesthetized and conscious animal. Micturition is due to an increase in pelvic parasympathetic activity and, in the cat, the anterior hypothalamus has been implicated in urinary bladder control with the demonstration of a dorsolateral vesicoconstrictor pathway and a ventromedial inhibitory pathway.

Effect of losartan microinjections into the NTS on the cardiovascular components of chemically evoked reflexes in a rabbit model of acute heart ischemia.

In the acute phase of myocardial infarction (MI) there are modifications of the autonomic outflow with an increase in the sympathetic tone and changes in cardiovascular reflexes. Activation of angiotensin AT1 receptors in the nucleus tractus solitarii (NTS) inhibits the baroreceptor and enhances the carotid chemoreflex. In this study, we investigated the role of NTS-AT1 receptors on the cardiovascular reflex responses evoked on stimulation of carotid chemoreflex and cardiac chemosensitive fibres in the acute phase of MI.

Angiotensin AT1 receptor antagonist losartan and the defence reaction in the anaesthetised rat. Effect on the carotid chemoreflex.

Modulation at the level of the nucleus tractus solitarii (NTS) appears to be an effective way of controlling cardiovascular reflexes. Angiotensin II acting on angiotensin AT1 receptors at the central nervous system appears to have an important role in these modulatory processes. The hypothalamic defence area (HDA) is a potential source of descending fibres containing angiotensin II that innervate the NTS.

Attenuation of the carotid body chemoreflex during the stimulation of the posterior vermis in the anaesthetised rabbit.

The purpose of this study was to investigate the effects of electrical and chemical stimulation of the sub-lobule IX-b of the cerebellar uvula on the cardiorespiratory responses evoked on stimulation of the carotid chemoreceptors in the anaesthetised and paralysed rabbit. Recordings of arterial blood pressure, ECG, heart rate and phrenic nerve activity were evaluated. Sub-lobule IX-b was activated electrically (1 ms, 20 microA, 100 Hz, 4-s train) and stimulated chemically with sodium glutamate microinjections (2 mM, pH=7.