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

✍ Scribed by Francisco J. Urbano; Felipe Sierra; Jorge A. Colombo; Jose M. Velasco; Washington Buño

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 192 KB
• Volume: 19
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/(sici)1098-1136(199702)19:2<161::aid-glia7>3.0.co;2-3

✦ Synopsis

Voltage-gated Na 1 currents (I Na ) were analysed 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 I Na types with different time-, voltage-dependent properties and tetrodotoxin (TTX) sensitivities were expressed in DM and CM. The I Na 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 (G Na ) half-activated (V 0A ) at 224 mV. I Na inactivation was fitted by single exponentials with 7.5 ms time constant (t h ) at the 235 mV half-inactivation voltage (V 0I ). I Na was not affected by 10 nM, was reduced (65%) by 100 nM, and not completely abolished (92%) by 300 nM tetrodotoxin (TTX). The I Na 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 G Na V 0A was 229 mV and inactivation was fitted by single exponentials with 2.6 ms t h at the 258 mV V 0I . This I Na 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'' I Na in DM and CM, respectively, suggesting that the CM contained diffusible trophic factors of astroglial origin that induced the expression of a different Na 1 channel type. About half of the CMand DM-plated cells also displayed a persistent Na 1 current (I NaP ).