Current clamp mode

Current clamp mode. In this mode the current is kept constant by the patch-clamp amplifier while voltage is measured, allowing recordings of the membrane potential. 

Figure 2 Hypoxia inhibits K+ channels in several 02-sensitive tissues, (a) Whole-ceU patch-clamp experiments show K" " current inhibition in response to hy poxia in rat resistance PASMCs. The complex I ETC blocker rotenone and the Kv blocker 4-aminopyridine (4-AP) also inhibit K" current, (b) Using the current clamp mode, resistance PASMCs depolarize in response to hypoxia. (From Ref. 29.) (c,d,e) Hypoxia inhibits outward K" " current in isolated cells from the NEB, CB, and PC-12 cells. (From Refs. 39,105,106.) Inset Proposed mechanism for HPy featuring the effector portion of the pathway.

Under these space-clamped conditions the action potential is referred to as a membrane action potential. With the switch shown in Fig. 5a in the voltage-clamp position, the membrane potential is under control. The problem was to switch from zero current to voltage-clamp mode quickly at various times during the membrane action potential. 

This is a true single-channel patch clamp mode allowing the measurement of singlechannel currents with the added benefit of making it possible to change the medium to which the intracellular surface of the membrane is exposed. Thus, the inside-out configuration is particularly valuable when studying the influence of intracellular molecules on ion channel function, like calcium or ATP. 

This is a true single-channel patch clamp mode allowing the measurement of single-channel currents with the... 

The Na+ current of NEB cells in rabbit neonatal lung slices exhibits fast activation and inactivation and is selectively carried by Na+ ions, since it is completely blocked by nanomolar concentrations of tetrodotoxin. The activation threshold of Na. was around —50 mV and reached maximal amplitude at —10 mV the mean peak current was 42.1 5.4pA with the range of 15-70pA. The Na+ current density was 18 3.9 pA pF and hypoxia failed to modify the amplitude of the Na+ current (9). In cultured NEB cells, Na+ current was activated at depolarizing voltages between —20 and —30 mV its peak was 282 pA and appeared to have both a TTX-sensitive and a TTX-insensitive component. In the current clamp recording mode, cultured... 

The action of phosphonic acid substituted calix[4]arenes (701)-(704) on solvent-containing planar bilayer membranes made of cholesterol and egg phosphatidylcholine (egg PC) or synthetic 18-carbon-tail phospholipid DOPC have been investigated in a voltage-clamp mode. A steady-state voltage-dependent transmembrane current has been achieved only after addition of the compound (702) from the side of the membrane the positive potential has been applied to. This current exhibited anion selectivity passing more chloride at negative potentials applied from the side of the membrane to which calix[4]arene (702) has been introduced. The kinetics and temperature-dependence determined for calix[4]arene (702)-mediated ionic transport suggested a carrier mode of facilitated diffusion. 

Researchers at the MoneU Center (Philadelphia, Pennsylvania) are using a variety of electrophysical and biochemical techniques to characterize the ionic currents produced in taste and olfactory receptor cells by chemical stimuli. These studies are concerned with the identification and pharmacology of the active ion channels and mode of production. One of the techniques employed by the MoneU researchers is that of "patch clamp." This method aUows for the study of the electrical properties of smaU patches of the ceU membrane. The program at MoneU has determined that odors stimulate intraceUular enzymes to produce cycUc adenosine 3, 5 -monophosphate (cAMP). This production of cAMP promotes opening of the ion channel, aUowing cations to enter and excite the ceU. MoneU s future studies wiU focus on the connection of cAMP, and the production of the electrical response to the brain. The patch clamp technique also may be a method to study the specificity of receptor ceUs to different odors, as weU as the adaptation to prolonged stimulation (3). 

The electrophysiological technique used to measure changes in membrane capacitance is the patch clamp [5,6] in the whole-cell recording mode, where the plasma membrane patch in the pipet is ruptured. In another configuration of the patch clamp, the plasma membrane patch is maintained intact. In this case, small currents due to the opening of individual channels can be measured in the membrane patch. The whole-cell patch clamp... 

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