Voltage-clamp

Anode-cathode / Voltage clamping device / monitoring Cathode shell... 

Electrophysiological studies (mainly using voltage-clamp and patch clamp) revealed the essential properties of the sodium channels kinetics of channel gating and selective ion permeation. Sodium channels are... 

Figure 4. Effects of dihydro-brevetoxin B (H2BVTX-B) on Na currents in crayfish axon under voltage-clamp. (A) A family of Na currents in control solution each trace shows the current kinetics responding to a step depolarization (ranging from -90 to -I-100 mV in 10 mV increments). Incomplete inactivation at large depolarizations is normal in this preparation. (B) Na currents after internal perfusion with H2BVTX-B (1.2 a M). inactivation is slower and less complete than in the control, and the current amplitudes are reduced. (C) A plot of current amplitudes at their peak value (Ip o, o) and at steady-state (I A, A for long depolarizations) shows that toxin-mOdified channels (filled symbols) activate at more negative membrane potentials and correspond to a reduced peak Na conductance of the axon (Reproduced with permission from Ref. 31. Copyright 1984 American Society for Pharmacology and Experimental Therapeutics).

Figure 5. Multiple actions of toxin II from Ammonia sulcata (ATX II) on voltage-clamped Na currents (Ij ) from amphibian myelinated nerve. This stabilizer toxin works in a dose-dependent manner to inhibit channel inactivation see bottom panel) and, as a consequence, delay the time of peak current see top panel). The reduction of peak current amplitude does not result directly from these kinetic alterations and is not observed with all stabilizers (Reproduced with permission from Ref. 39. Copyright 1981 SPPIF).

Figure 2.12 From voltage-clamp to current-clamp micro-electrode recordings of synaptic current (/, lower trace) and synaptic potential with superimposed action potential (V, upper trace) from a neuron in an isolated rat superior cervical sympathetic ganglion following a single stimulus (S) applied to the preganglionic nerve trunk. The interval between the stimulus and the postsynaptic response includes the conduction time along the unmyelinated axons of the preganglionic nerve trunk. (SJ Marsh and DA Brown, unpublished)...

Whole-cell Voltage-Clamp Recordings of Na/K Pump Current Effects of Cellular Glutathione Manipulation... 

Karagueuzian, H.S. and Katzung, B.G. (1982). Voltage-clamp studies of transient inward current and mechanical oscillations induced by ouabain in ferret papillary muscle. J. Physiol, 327, 255-271. 

Shattock M. J. and Matsuura, H. (1993). Measurement of Na -K pump current in isolated rabbit ventricular myocytes using the whole-cell voltage-clamp technique. Inhibition of the pump by oxidant stress. Circ. Res. 72, 91-101. 

The study of processes at ITIES and in membrane electrochemistry requires elimination of two ohmic potential differences, achieved with a four-electrode potentiostat, voltage-clamp (Fig. 5.17). 

Fig. 5.17 A four-electrode potentiostatic circuit (voltage clamp). and R2 are reference electrodes with Luggin capillaries (arrows) attached as close as possible to the membrane or ITIES (dashed line), B, and B2 are auxiliary electrodes, P and P2 potentio-stats, G programmed voltage generator and Z recorder... 

Fig. 6.21 Joint application of patch-clamp and voltage-clamp methods to the study of a single potassium channel present in the membrane of a spinal-cord neuron cultivated in the tissue culture. The values indicated before each curve are potential differences imposed on the membrane. The ion channel is either closed (C) or open (O). (A simplified drawing according to B. Hille)...

The opening of masses of ion channels in nematode muscle membranes may be detected using the two-microelectrode voltage-clamp technique. In contrast, the opening of single ion channels may be recorded using the vesicle preparation and patch-clamp technique. These techniques are both described below. 

Imidazopyridazines DM1 (16) and DM2 (17), originally prepared as cyclooxygenase inhibitors, have demonstrated T-type antagonist properties in voltage clamp studies using the Cav3.1 subtype, as well as seizure suppression in WAG/Rij rats at 1, 3, and 10 mg/kg. The potency of these compounds toward the block of other ion channels was not reported [58]. 

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