[2 calcium currents in the somatic membrane of neurons of Helix pomatia].
Two different calcium currents were revealed in the somatic membrane of Helix pomatia neurons. In addition to the main current described in literature, depolarizing the membrane from the holding potential level (-120 divided by -100 mV) an additional calcium current was observed. It was activated at depolarizations to -80 divided by -40 mV. Contrary to the main calcium current it did not deteriorate during intracellular perfusion by solutions containing fluoride. Time-dependence of this current could be described in the framework of the Hodgkin-Huxley model with time constants for activation and inactivation equal to tau m = 6-8 ms and tau h = 300-600 ms, respectively. The amplitude of this current increased with increase of extracellular Ca2+ concentration and decreased after addition of Co2+, Ni2+, Cd2+, nifedipine and verapamil. Dissociation constants of these substances with corresponding channels determined for the maximum of current-voltage relationship were 2 (Ca2+), 3 (Co2+), 0.06 (nifedipine) and 0.2 mmol/l (verapamil). Properties of the fluoride-insensitive calcium current and data obtained for other calcium channels are compared. Its possible functional role is also discussed.
S L
SL
Mironov
A V
AV
Tepikin
A V
AV
Grishchenko
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D003035:Cobalt / Q000494:pharmacology; D006372:Helix, Snails; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials; D009474:Neurons / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D007473:Ion Channels; D003035:Cobalt; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium
Dva kal'tsievykh toka v somaticheskoĭ membrane neĭronov vinogradnoĭ ulitki.