Calcium currents in internally perfused nerve cell bodies of Limnea stagnalis

作者：Lou Byerly, Susumu Hagiwara · 发表于：The Journal of Physiology · 年份：1982 · DOI：10.1113/jphysiol.1982.sp014052 · 被引用次数：240 · 研究领域：Neuroscience and Neural Engineering、Ion channel regulation and function、Neurobiology and Insect Physiology Research

1. When K(+) is removed from both sides of the somal membrane of Limnea neurones, time-dependent, voltage-dependent outward currents are observed at positive potentials. These currents can be carried by Tris(+) and tetraethylammonium (TEA(+)), as well as Cs(+), but the Cs currents are several times larger. The Cs currents are not affected by external or internal TEA, but are strongly reduced by 4-aminopyridine (4-AP) and all Ca blockers tried.2. The presence of these non-specific outward currents and their sensitivity to all treatments that eliminate the Ca currents prevent the complete isolation of Ca currents. The non-specific outward currents are most prominent at large positive potentials and as slow tail currents on stepping back to the holding potential.3. Ca currents are ;washed out' in well perfused cells. Typically the Ca current has decayed to less than one tenth of its original size after (1/2) h of perfusion. This wash-out is specific for the Ca current; Na and K currents persist for several hours.4. Once the Ca current has completely decayed, it is possible to study one type of non-specific current without overlapping inward currents. This current activates between 0 and +30 mV and appears to reverse near 0 mV.5. In spite of the probable presence of slowly activating outward currents, the net inward currents measured show little apparent inactivation. In all the cells studied the inward current evoked at +20 mV has never decayed by more than 50% during a 60 ms pu...