Sub-cellular Electrical Heterogeneity Revealed by Loose Patch Recording Reflects Differential Localization of Sarcolemmal Ion Channels in Intact Rat Hearts.

The cardiac action potential (AP) is commonly recoded as an integral signal from isolated myocytes or ensembles of myocytes (with intracellular microelectrodes and extracellular macroelectrodes, respectively). These signals, however, do not provide a direct measure of activity of ion channels and transporters located in two major compartments of a cardiac myocyte: surface sarcolemma and the T-tubule system, which differentially contribute to impulse propagation and excitation-contraction (EC) coupling. In the present study we investigated electrical properties of myocytes within perfused intact rat heart employing loose patch recording with narrow-tip (2 μm diameter) extracellular electrodes.

The role of luminal Ca regulation in Ca signaling refractoriness and cardiac arrhythmogenesis.

Györke et al. discuss the role of sarcoplasmic reticulum Ca in cardiac refractoriness and pathological implications.

Muscarinic Stimulation Facilitates Sarcoplasmic Reticulum Ca Release by Modulating Ryanodine Receptor 2 Phosphorylation Through Protein Kinase G and Ca/Calmodulin-Dependent Protein Kinase II.

Although the effects and the underlying mechanism of sympathetic stimulation on cardiac Ca handling are relatively well established both in health and disease, the modes of action and mechanisms of parasympathetic modulation are poorly defined. Here, we demonstrate that parasympathetic stimulation initiates a novel mode of excitation-contraction coupling that enhances the efficiency of cardiac sarcoplasmic reticulum Ca store utilization. This efficient mode of excitation-contraction coupling involves reciprocal changes in the phosphorylation of ryanodine receptor 2 at Ser-2808 and Ser-2814.

Two types of extracellular action potentials recorded with narrow-tipped pipettes in skeletal muscle of frog, Rana temporaria.

Two types of muscle fibre action potentials (APs) were recorded using narrow-tipped extracellular pipettes in isolated sartorius muscles of frog, Rana temporaria. The waveform of type 1 responses (T1 AP, 75% of recordings) was biphasic, 'positive–negative.' The type 2 signals were tri-phasic, 'positive–negative–positive' (T2 AP, 18%).