The calcium action potential and a prolonged calcium dependent after-hyperpolarization in mouse neuroblastoma cells.
1. Action potentials elicited in solutions with elevated [Ca2+] (1.8-40 mM) have been studied in differentiated cells of mouse neuroblastoma clone N1E-115 in tissue culture. 2. The action potential in high [Ca2+] solutions containing eithr Na+ or Tris is followed by a prolonged after-hyperpolarization (a.h.p.) lasting 0.5-4 sec. The a.h.p. reverses sign between -75 and -85 mV. 3. Externally applied tetraethylammonium (TEA, 15 mM) increases the Ca2+ spike overshoot, prolongs the falling phase and enhances the a.h.p. duration. The a.h.p. is inhibited by Ca2+ antagonists such as La3+, Co2+ and Mn2+. 4. After replacement of Ca2+ by Ba+ or Sr2+ (20mM) action potentials can still be elicited in Na+-free solution, but no a.h.p. is observed. 5. Increasing [Ca2+] from 1.8 up to 20 mM results in an increased capability of neuroblastoma cells to fire repetitively and in a consistent reduction of the firing rate from about 4-10 sec-1 to 0.5-1.8 sec-1. 6. It is concluded that Ca2+ entry during the action potential activates a TEA-resistant K+ conductance which gives rise to the prolonged a.h.p. Data from repetitively firing cells are consistent with the view that the a.h.p. plays a role in the regulation of low-frequency firing.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002999:Clone Cells / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology; D051379:Mice; D009447:Neuroblastoma / Q000503:physiopathology*; D013324:Strontium / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D013757:Tetraethylammonium Compounds; D001464:Barium; D008274:Magnesium; D002118:Calcium; D013324:Strontium