Activity-dependent survival of rat cerebellar granule neurons is not associated with sustained elevation of intracellular Ca2+

Ca2+ plays a pivotal role for the activity-dependent survival of neurons. In primary culture of cerebellar granule neurons, we found that there is no significant difference in intracellular Ca2+ level in the survival-promoting condition (cultures in the presence of 25 mM KCl) and that in the apoptosis-inducing condition (cultures in the presence of 5 mM KCl). This was not due to the inactivation of voltage-dependent L-type Ca2+ channels in the survival-promoting condition, but due to the enhanced rate of the influx and the efflux of Ca2+ in the survival-promoting condition compared to that in the apoptosis-inducing condition. These results suggest that the activity-dependent survival of the granule neurons is not associated with sustained rise of intracellular Ca2+ but associated with the enhanced turnover rate of Ca2+.