The effect of known K+-channel blockers on the electrical activity of bovine lymphatic smooth muscle.
The effects of known K+-channel blockers on the electrical properties of bovine lymphatic smooth muscle were investigated using the double sucrose-gap technique. Constant current anodal pulses elicited hyperpolarizing electrotonic potentials (EP's) which were characterised by a "sag" in the potential record. Current/voltage relationship (I/V), which were examined by measuring EP amplitude at the end of 5 s anodal pulses (less than 30 microA), showed an apparent increase in conductance with increasing hyperpolarization. In the presence of caesium (10 mM), 4-aminopyridine (10 mM) or in the absence of external K+ the sag in the EP was lost and the inward rectification characteristic of the control I/V relationship was abolished. Barium (2.5 mM) also abolished in sag in the EP although TEA (10 mM) had no effect on either EP shape or I/V relationship. Thus it would appear that lymphatic smooth muscle shows inward rectification which is slowly activating and is blocked by some of the known K+-channel blockers or by the removal of external K+.
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002417:Cattle; D002586:Cesium / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008208:Lymphatic System / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
D000631:Aminopyridines; D007473:Ion Channels; D013757:Tetraethylammonium Compounds; D002586:Cesium; D001464:Barium; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D011188:Potassium