Voltage-gated sodium channels (VGSC) regulate neuronal excitability by governing action potential (AP) generation and propagation. Recent studies have revealed that AMP-activated protein kinase (AMPK) activators decrease sensory neuron excitability, potentially by preventing sodium (Na+) channel phosphorylation by kinases such as ERK or via modulation of translation regulation pathways. The dir...

OBJECTIVE The aim of this study was to investigate changes following regression of left ventricular hypertrophy (LVH). METHODS Electrophysiolological changes were recorded in isolated guinea-pig myocardial preparations. LVH was induced by constriction of the thoracic aorta and regression was followed after removal of the constriction. Sham-operated animals served as controls. RESULTS During...

The mechanisms underlying many important properties of the human atrial action potential (AP) are poorly understood. Using specific formulations of the K+, Na+, and Ca2+ currents based on data recorded from human atrial myocytes, along with representations of pump, exchange, and background currents, we developed a mathematical model of the AP. The model AP resembles APs recorded from human atri...

The operation of neuronal networks depends on the firing patterns of the network's neurons. When sustained current is injected, some neurons in the central nervous system fire a single action potential and others fire repetitively. For example, in Xenopus laevis tadpoles, primary-sensory Rohon-Beard (RB) neurons fired a single action potential in response to 300-ms rheobase current injections, ...

In the last several years, a promising new approach has been suggested in the therapy of Ménière's disease (MD): the low-dose intratympanic gentamicin therapy. By titrating the desired vestibular inhibition by single injections and infrequent administration, side effects concerning hearing can be held on an acceptably low level, while disease-related symptoms are often successfully eliminated. ...

Transgenic mice have been increasingly utilized to investigate the molecular mechanisms of cardiac arrhythmias, yet the rate dependence of the murine action potential duration and the electrical restitution curve (ERC) remain undefined. In the present study, 21 isolated, Langendorff-perfused, and atrioventricular node-ablated mouse hearts were studied. Left ventricular and left atrial action po...

BACKGROUND Oxidative stress plays an important role in the pathophysiology of atrial fibrillation (AF). The hydrogen peroxide (H2O2) mainly underlies the cellular oxidative stress and free radicals. Left atrium (LA) is the most important AF substrate. However, the effects of H2O2 on the action potential (AP) and ionic currents in LA myocytes have not been fully elucidated. METHODS The whole-c...

HERG K(+) channel, the genetic counterpart of rapid delayed rectifier K(+) current in cardiac cells, is responsible for many cases of inherited and drug-induced long QT syndromes. HERG has unusual biophysical properties distinct from those of other K(+) channels. While the conventional pulse protocols in patch-clamp studies have helped us elucidate these properties, their limitations in assessi...

BACKGROUND The primary mechanism of tissue injury by radiofrequency catheter ablation is presumed to be thermally mediated. However, the myocardial cellular electrophysiological effects of hyperthermia are not well characterized. We used an in vitro model of isolated guinea pig right ventricular papillary muscle to investigate the acute cellular electrophysiological effects of hyperthermia. M...

OBJECTIVES We investigated the hypothesis that re-entrant pulmonary vein (PV) tachycardias may serve as a mechanism for initiating and sustaining paroxysmal atrial fibrillation (PAF). BACKGROUND The mechanisms of rapid repetitive discharges from the PV initiating PAF remain incompletely understood. Pulmonary vein myocardial sleeves appear to provide a favorable substrate for re-entry formatio...