ABSTRACT
On rat retinal preparation in whole-cell mode retinal ganglion cells (RGC) tonic firing induced calcium signals were recorded and their modulation by Kv3 potassium channels was studied. RGC depolarization with 500 ms current steps caused tonic action potentials (AP) generation and development of calcium signals which amplitude depended quite linearly on mean AP frequency with mean slope 1.4 +/- 0.2 s x nmol/l (n = 5). The calcium signals mean tau of decay value was 6.8 +/- 1.4 s (n = 5). After application of tetraethylammoniun (500 MM), which in such concentration blocks Kv3.1/Kv3.2 potassium channels, a decrease in firing frequency, an increase of AP width and a decrease of afterhyperpolarization amplitude were observed. In the presence of the blocker the calcium signal amplitude vs mean AP frequency dependency slope mean value increased to 2.1 +/- 0.3 s.nmol/l. The calcium signals tan of decay not changed significantly, the mean value was 8.9 +/- 1.6 s (n = 5). Thus, voltage-dependent Kv3.1/Kv3.2 potassium channels, which play a key role in tonic firing pattern generation in RGC, also modulate appropriate calcium signals and prevent the cells from significant intracellular calcium increasing and its possible cytotoxic action.
