Although there is substantial evidence of abnormal Ca2+ homeostasis in heart cells of the cardiomyopathic Syrian hamster (Bio 14.6 strain), the mechanism by which these myocytes become Ca(2+)-overloaded is not known. To elucidate the role of voltage-sensitive Ca2+ channels in the pathogenesis of myopathy, whole-cell Ca2+ currents were measured in myopathic and normal control cardiac myocytes. T...

We report an ion channel in the plasma membrane of unfertilized oocytes of the ascidian Ciona intestinalis that is directly gated by the second messenger ADP-ribose. The ion channel is permeable to Ca2+ and Na+ and is characterized by a reversal potential between 0 and +20 mV and a unitary conductance of 140 pS. Preinjection of the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane- N, N, N', N'-tetra...

The cacophony (cac) locus in Drosophila encodes a Ca2+ channel alpha subunit, but little is known about properties of cac-mediated currents and functional consequences of cac mutations in central neurons. We found that, in Drosophila cultured neurons, Ca2+ currents were mediated predominantly by the cac channels. The cac channels contribute to low- and high-threshold, fast- and slow-inactivatin...

Evidence from pharmacological studies suggests that induction of the acrosome reaction of mammalian spermatozoa by solubilized zona pellucida, and possibly by progesterone, is dependent upon Ca2+ influx through voltage-operated Ca2+ channels. Studies on Ca2+ accumulation and membrane potential in ligand-stimulated or artificially depolarized spermatozoa support such a conclusion. Electrophysiol...

The mechanism of depressant effects of Ca2+ on the acetylcholine (ACh)-activated ion channel conductance was studied in frog muscle fibers. Increasing the extracellular Ca2+ ( (Ca2+)o) suppressed the increase in the end-plate conductance induced by iontophoretic application of ACh and shifted the reversal potential for a neurally-induced end-plate current to a more negative value. The single ch...

Electrogenic ion transport through the colon epithelium of the African clawed toad (Xenopus laevis) was investigated with electrophysiological methods in vitro. Interest was focused on a previously described phenomenon, that removal of Ca2+ from the mucosal Ringer's solution increases electrogenic sodium absorption. Our results clearly show that Ca2+ removal reveals an apical ion channel that i...

A Cl- channel with a small single-channel conductance (3 pS) was observed in cell-attached patches formed on the apical membrane of cells from the distal nephron cell line (A6) cultured on permeable supports. The current-voltage (I-V) relationship from cell-attached patches or inside-out patches with 1 microM cytosolic Ca2+ strongly rectified with no inward current at potentials more negative t...

Interstitial cells of Cajal (ICC) generate the electrical slow wave. The ionic conductances that contribute to the slow wave appear to vary among species. In humans, a tetrodotoxin-resistant Na+ current (Na(V)1.5) encoded by SCN5A contributes to the rising phase of the slow wave, whereas T-type Ca2+ currents have been reported from cultured mouse intestine ICC and also from canine colonic ICC. ...

1. A detailed compartmental model of a cerebellar Purkinje cell with active dendritic membrane was constructed. The model was based on anatomic reconstructions of single Purkinje cells and included 10 different types of voltage-dependent channels described by Hodgkin-Huxley equations, derived from Purkinje cell-specific voltage-clamp data where available. These channels included a fast and pers...