Ionic channel currents in cultured neurons from human cortex.
Ionic channels in human cortical neurons have not been studied extensively. HCN-1 and HCN-1A cells, which recently were established as continuous cultures from human cortical tissue, have been shown by histochemical and immunochemical methods to exhibit a neuronal phenotype, but expression of functional ionic channels was not demonstrated. For the present study, HCN-1 and HCN-1A cells were cultured in Dulbecco's modified Eagle's medium with 15% fetal calf serum, in some cases supplemented with 10 ng/ml nerve growth factor, 10 microM forskolin, and 1 mM dibutyryl cyclic adenosine monophosphate to promote differentiation. Cells or membrane patches were voltage clamped using conventional patch clamp techniques. In HCN-1A cells, we identified a tetrodotoxin-sensitive Na+ current, two types of Ca2+ channel current, including L-type current and a second type that in some respects resembled N-type current, and four types of K+ current, including a delayed outward rectifier that showed voltage-dependent inactivation, two types of noninactivating Ca(2+)-activated K+ channels with slope conductances of 146 and 23 pS (K+i/K+o 145 mM/5 mM), and less frequently, a noninactivating, intermediate conductance channel that was not sensitive to internal Ca2+. When HCN-1A cells were examined after 3 days of exposure to differentiating agents, pronounced morphological changes were evident but no differences in ionic currents were apparent. HCN-1 cells also exhibited K+ and Ca2+ channel currents, but Na+ currents were not detected in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Simard
J M
JM
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77550.
Song
Y
Y
Tewari
K
K
Dunn
S
S
Werrbach-Perez
K
K
Perez-Polo
J R
JR
Eisenberg
H M
HM
D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D004594:Electrophysiology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects*; D009474:Neurons / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism
D015220:Calcium Channels; D007473:Ion Channels; D015221:Potassium Channels; D015222:Sodium Channels