Dual role of ryanodine-sensitive calcium stores in central neurons

The ryanodine-sensitive intracellular Ca2+ stores are known to play a major role in excitation-contraction coupling in muscles. Although these stores are also abundantly present in central neurons, their functional role in these cells remains unclear. Using fluorometric digital imaging of the intracellular Ca2+ concentration ([Ca2+]i) in rat hippocampal slices, we investigated the dynamic properties of the ryanodine-sensitive Ca2+ stores inCA1 hippocampal pyramidal cells. We found that at rest the ryanodine-sensitive Ca2+ stores are functioning predominantly as a “sink” for Ca ions responding to an increase in [Ca2+]i with an increase in the amount of Ca ions accumulated inside the stores. If, however, [Ca2+]i increases significantly, as happens during strong neuronal discharges, the ryanodine-sensitive Ca2+ stores respond with Ca2+ release, thus acting as an amplifier of the intracellular Ca2+ signal.