Changes in Intracellular Calcium Ion Concentrations during Generation of High-Amplitude EPSP in Neurons in the Common Snail

摘要

Changes in intracellular calcium ion concentrations are the main trigger for most physiological processes in neurons, including changes in gene expression and the processes of synaptic plasticity. Our experiments showed that high-amplitude EPSP in common snail command neurons, like action potentials, are accompanied by marked increases in intracellular calcium ion concentrations. The amplitude of calcium signals accompanying high-amplitude EPSP in command neurons was found to depend linearly on the strength of synaptic stimulation, while the dynamics of changes in the amplitude of EPSP themselves showed marked saturation as stimulus strength increased. This means that over a certain range of changes of membrane potential, calcium signals transmit stimulus strength more adequately than the level of depolarization of the postsynaptic neuron. We suggest that calcium signals evoked by high-amplitude EPSP can induce biochemical changes in neurons, thus mediating cellular responses in the range subthreshold for action potentials.