Neural progenitor cells (NPCs) can generate all cell types of the central nervous system. Electrophysiological investigations of NPCs revealed voltage activated K⁺ currents and an 1-EBIO activated and scyllatoxin (ScTX) sensitive K⁺ current (K_d= 1.9 ±0.3 nM). The strongest SK channel expression in NPCs was observed for SK3 transcripts. Immunocytochemical experiments revealed the expression of SK3 proteins in almost all NPCs. Using pre-embedding immunoelectron microscopy it was possible to localise SK3 proteins in short filopodia like structures (FLS) with a length of approximately 0.3 to 1.0 mM. Time lab experiments were performed using Richardson Contrast Microscopy, which enabled us to visualise the FLS in living cells. Outgrowing and retracting FLS were observed under control conditions. The application of 1-EBIO to the bath solution led to a simultaneous outgrowth of FLS within 2 to 5 min after application up to a final length of 30 mm. The sprouting could be prevented by a pre-incubation with 50 nM ScTX. We conclude that SK3 channel activity is involved in triggering the sprouting of FLS in NPCs.

Supported by: 4SC, Martinsried (to SG), Medizinische Fakultät, Ulm, P770 (to OW) and P868 (to SL)