The state dependence of Na channel modification by batrachotoxin (BTX) was investigated in voltage-clamped and internally perfused squid giant axons before (control axons) and after the pharmacological removal of the fast inactivation by pronase, chloramine-T, or NBA (pretreated axons). In control axons, in the presence of 2-5 microM BTX, a repetitive depolarization to open the channels was req...

ATP-sensitive potassium (K(ATP)) channels are heteromultimer complexes of subunits from members of the inwardly rectifying K(+) channel and the ATP-binding cassette protein superfamilies. K(ATP) channels couple metabolic state to membrane excitability, are distributed widely, and participate in a variety of physiological functions. Understood best in pancreatic beta cells, where their activatio...

Phosphatidylinositol 4,5-bisphosphate (PIP2) regulates Shaker K+ channels and voltage-gated Ca2+ channels in a bimodal fashion by inhibiting voltage activation while stabilizing open channels. Bimodal regulation is conserved in hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, but voltage activation is enhanced while the open channel state is destabilized. The proposed sites o...

introduction: we have recently reported the presence of two potassium currents with 598 and 368 ps conductance in the rough endoplasmic reticulum (rer) membrane. the 598 ps channel was voltage dependent and atp sensitive. however, the 368 ps channel was rarely observed and its identity remained obscure. since cationic channels in intracellular organelles such as mitochondria and rer play import...

The kinetic properties of tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na' channels in acutely dissociated neonatal rat trigeminal ganglion neurons were studied using whole-cell and cell-attached patch-clamp recordings. The time course of TTX-R currents was slower than that of TTX-S currents. Compared with TTX-S currents, TTX-R currents had more positive half-activation and...

Transmembrane ionic movements are thought to occur through special membrane areas or channels. Until recently, it has not been possible to study the properties of individual ionic channels, directly. We have used the extracellular patch clamp technique to resolve unitary sodium channels in enzyme-dissociated rabbit ventricular myocytes. Depolarizing voltage clamp steps elicited rectangular inwa...

Cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels are gated by binding and hydrolysis of ATP at the nucleotide-binding domains (NBDs). We used covalent modification of CFTR channels bearing a cysteine engineered at position 334 to investigate changes in pore conformation that might accompany channel gating. In single R334C-CFTR channels studied in excised patches, mod...

Living cells respond to mechanical forces applied to their outer membrane through processes referred to as "mechanosensation". Faced with hypotonic shock, to circumvent cell lysis, bacteria open large solute-passing channels to reduce the osmotic pressure gradient. In the vascular beds of vertebrate animals blood flow is regulated directly through mechanical distention-induced opening of stretc...