1. The effects of the cardioactive peptide FMRFamide were tested on enzymatically dissociated muscle cells isolated from hearts of the leech. These cells were normally quiescent, with resting potentials near -60 mV. 2. Superfusion of FMRFamide induced a strong depolarization in isolated heart cells (e.g., >40 mV with 10v6 M FMRFamide). The depolarization was maintained in the continued presence...

A sustained high voltage-activated (HVA), nifedipine- and cadmium-sensitive calcium current and a sustained calcium action potential (AP) were recorded from horizontal cells isolated from catfish retina. pH indicator dyes showed that superfusion with NH4Cl alkalinized these cells and that washout of NH4Cl or superfusion with Na-acetate acidified them. HVA current was slightly enhanced during su...

A large reduction of intracellular potassium activity in depolarized subendocardial Purkinje fibers 24 hours after coronary artery ligation is accompanied by a much smaller increase in intracellular sodium activity. Similar intracellular ionic changes also occur during acute ischemia in ventricular muscle and are consistent with mechanisms based on intracellular acidification, which is known to...

To determine whether canine epicardium and endocardium show intrinsically different electrophysiological responses to metabolic alterations that occur during acute myocardial ischemia in vivo, endocardial, epicardial, papillary muscle tip, and Purkinje fibers (PF) were superfused in vitro with Tyrode's solution containing 8.0 DM KC1 at a pH of 6.85 and a Po2 < 50 mm Hg. During the initial 10 mi...

Background:To investigate the mechanisms of myocardial ischemia induced changes of electrophysiological properties, influences of various ischemic-simulated Tyrode’s solutions on the changes of action potential characteristics were examined. Method:Action potential characteristics were measured during superfusion with various ischemic-simulated solutions (modified physiologic salt solution;MPSS...

Central sensitization is a crucial process underlying the increased neuronal excitability of nociceptive pathways following peripheral tissue injury and inflammation. Our previous findings have suggested that extracellular adenosine 5'-triphosphate (ATP) molecules acting at purinergic receptors located on presynaptic terminals (e.g., P2X2/3, P2X3 subunits) and glial cells are involved in the gl...