Functional changes in sodium conductances in the human neuroblastoma cell line SH-SY5Y during in vitro differentiation.
1. The electrophysiological properties of voltage-dependent sodium currents were studied in the human neuroblastoma cell line SH-SY5Y before and after in vitro differentiation with retinoic acid, with the use of the whole cell variant of the patch-clamp technique. 2. Voltage steps from a holding level of -90 mV to depolarizing potentials elicited, in both undifferentiated and differentiated cells, fast inward sodium currents that were full inactivating and tetrodotoxin sensitive. 3. In undifferentiated cells the current peaked at -10 mV, the half-activation potential was -35 mV, and the half-inactivation potential was -81 mV. In differentiated cells the current peaked at + 10 mV, the half-activation potential was -28 mV, and the half-inactivation potential was -56 mV. Moreover, the peak current amplitude was about a factor of 2 larger and inactivation kinetics was about a factor of 2 slower than in undifferentiated cells. 4. This diversity in sodium channel properties was related to differences in cell excitability. Under current-clamp conditions, intracellular injection of rectangular depolarizing current stimuli from a hyperpolarized membrane potential of about -100 mV elicited graded and weak regenerative responses in undifferentiated cells, whereas overshooting action potentials with faster rising phases could be elicited in differentiated cells.
Toselli
M
M
Istituto di Fisiologia Generale, Universitá di Pavia, Italy.
Tosetti
P
P
Taglietti
V
V
D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012044:Regression Analysis; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015222:Sodium Channels; D013779:Tetrodotoxin; D014212:Tretinoin