Appearance of highly sensitive cells to L-type Ca antagonist in cultured cerebellar granule cells

We studied intracellular Ca2+ ([Ca2+]i) kinetics within single cells using and image-analyzing system. We prepared a culture dish with a bottom made of quartz (non-fluorescent glass) for reducing the background fluorescence during [Ca2+]i measurement. Furthermore, we changed the concentration of the poly-L-lysine solution which had been used to make cells adhere to the dish bottom from the conventional 5 micrograms/ml to 15 micrograms/ml. This modification improved cell viability, prevented colony formation, and therefore, provided favorable cell samples for detection within single cells. Then, we investigated 25 mM KCl-evoked changes in the [Ca2+]i level of rat cerebellar granule cells. We found that sensitivity to KCl was high in some cells but low in others. In a study using the highly sensitive cells, nicardipine, nimodipine and nifedipine were active even at nanomolar or picomolar levels, although their affinities to the L-type Ca ion channel have been reported to act only at micromolar levels.