?Different voltage-gated sodium currents are expressed by human neuroblastoma NB69 cells when cultured in defined serum-free and in astroglial-conditioned media

URBANO, FJ; SIERRA F; COLOMBO JA; VELASCO JM; BUÑO W

GLIA

Wiley-Liss Inc.

Lugar: New York, USA; Año: 1997 vol. 19 p. 161 - 170

0894-1491

Voltage-gated Na currents (INa) were analyzed with the whole-cell patch-clamp technique in human neuroblastoma NB69 cells plated in serum-free ??defined?? medium (DM) or in ??astroglial-conditioned?? medium (CM). Cells survived in both media and expressed the microtubule associated protein 1A, indicating neuron-like differentiation. Two INa types with different time-, voltage-dependent properties and tetrodotoxin (TTX) sensitivities were expressed in DM and CM. The INa in DM-plated cells was present from day 4 and its surface density increased from 11 pA/pF (days 5?7) to 68 pA/pF (days 15?30). The underlying conductance (GNa) half-activated (V0A) at -24 mV. INa inactivation was fitted by single exponentials with 7.5 ms time constant (th) at the -35 mV half-inactivation voltage (V0I). INa was not affected by 10 nM, was reduced (65%) by 100 nM, and not completely abolished (92%) by 300 nM tetrodotoxin (TTX). The INa of CM-plated cells appeared at day 3?4 and its surface density increased from 14 pA/pF (days 3?6) to 28 pA/pF (days 11?14). The GNa V0A was -29 mV and inactivation was fitted by single exponentials with 2.6 ms th at the 258 mV V0I. This INa was reduced (55%) by 10 nM and totally abolished by 100 nM tetrodotoxin (TTX). In conclusion, NB69 cells displayed a slow, ??TTX-resistant,?? or a fast, ??TTX-sensitive?? INa in DM and CM, respectively, suggesting that the CM contained diffusible trophic factors of astroglial origin that induced the expression of a different Na1 channel type. About half of the CM and DM-plated cells also displayed a persistent Na current (INaP).