Search results for "Voltage clamp"
showing 4 items of 14 documents
ACTION POTENTIAL, MEMBRANE CURRENTS AND FORCE OF CONTRACTION IN MAMMALIAN HEART MUSCLE FIBRES TREATED WITH QUINIDINE
1978
The effects of quinidine on electrical and mechanical activity were investigated in atrial and/or ventricular heart muscle preparations from guinea pigs and cats. Quinidine (1--100 micrometer) exerted negative inotropic effects in papillary muscles from guinea pigs and cats. In guinea-pig left atria, a positive inotropic effect was superimposed on the negative inotropic effect in response to quinidine. Quinidine (100 micrometer) prolonged the duration of the action potential in guinea-pig atria but shortened it in guinea-pig ventricular muscle. In cat papillary muscles, the late repolarization was markedly prolonged by quinidine, but virtually no change of the plateau phase was observed. Th…
Modulation of voltage-gated Na+ and K+ channels by pumiliotoxin 251D: A “joint venture” alkaloid from arthropods and amphibians
2008
Abstract Certain amphibians provide themselves with a chemical defense by accumulating lipophilic alkaloids into skin glands from dietary arthropods. Examples of such alkaloids are pumiliotoxins (PTXs). In general, PTXs are known as positive modulators of voltage-gated sodium channels (VGSCs). Unlike other PTXs, PTX 251D does not share this characteristic. However, mice and insect studies showed that PTX 251D is highly toxic and to date the basis of its toxicity remains unknown. In this work, we searched for the possible target of PTX 251D . The toxin was therefore made synthetically and tested on four VGSCs (mammalian rNa v 1.2/β 1 , rNa v 1.4/β 1 , hNa v 1.5/β 1 and insect Para/tipE ) and…
Monovalent cation conductance in Xenopus laevis oocytes expressing hCAT-3
2005
hCAT-3 (human cationic amino acid transporter type three) was investigated with both the two-electrode voltage clamp method and tracer experiments. Oocytes expressing hCAT-3 displayed less negative membrane potentials and larger voltage-dependent currents than native or water-injected oocytes did. Ion substitution experiments in hCAT-3-expressing oocytes revealed a large conductance for Na + and K + . In the presence of l-Arg, voltage-dependent inward and outward currents were observed. At symmetrical (inside/outside) concentrations of l-Arg, the conductance of the transporter increased monoexponentially with the l-Arg concentrations; the calculated Vmax and KM values amounted to 8.3 AS and…
Adenosine activates a potassium conductance in guinea-pig atrial heart muscle.
1983
Adenosine shortens the action potential and diminishes the force of contraction in guinea-pig left atria. These effects may be brought about by the activation of a potassium conductance. This assumption is supported by voltage clamp and 42K release experiments.