Calcium Ion Influx and Release in Aplysia Bag Cell Neurons

Pharmacological activation of a non-selective cation channel that drives the afterdischarge, produced inward current and, as assessed by Mn 2+-quench of fura, Ca2+ entry. This receptor-operated Ca2+ influx pathway may contribute to plasticity or secretion. Voltage-gated Ca2+ influx was investigated using trains of action potentials delivered at 5 Hz, 10 s (mimicking the synaptic input that initiates the afterdischarge) or 5 Hz, 1 min (mimicking the fast phase of the afterdischarge). While both trains transiently elevated intracellular Ca2+, only the 5 Hz, 1 min stimulus produced a Ca2+ rise that markedly outlasted the initial influx, consistent with Ca2+-induced Ca2+ release (CICR). Thus, robust Ca2+ influx is required to trigger bag cell neuron CICR.