Control of Action Potential-Induced Ca²⁺Signaling in the Soma of Hippocampal Neurons by Ca²⁺Release from Intracellular Stores

Abstract

Stimulus-induced increases in neuronal CaHere we used fluorescent Ca 2ϩ measurements in cultured hippocampal neurons and report that the amplitude of the somatic Ca 2ϩ increase triggered by field stimulation is independent of the extracellular Ca 2ϩ concentration as long as the concentration is greater than 50 M. Furthermore, significantly more La 3ϩ has to be added extracellularly for blocking Ca 2ϩ responses, as predicted from the reported La 3ϩ dependence of voltage-gated Ca 2ϩ channels. These measurements suggest that field stimulation-induced somatic Ca 2ϩ responses in hippocampal neurons are largely attributable to Ca 2ϩ release from intracellular stores. Only a small number of Ca 2ϩ ions have to enter across the plasma membrane for this intracellular Ca 2ϩ amplification process to occur. Rapid fluorescence-imaging measurements showed that the internal Ca 2ϩ amplification occurs over 10 -15 msec and linearly increases intracellular Ca 2ϩ concentrations for up to 40 action potentials. At a fixed number of field pulses, frequencies of 40 Hz were optimal for somatic Ca 2ϩ increases. Our studies suggest that the opening of intracellular Ca 2ϩ release channels plays a crucial part in shaping the action potential-induced neuronal Ca 2ϩ response.

Neurotrophin secretion from hippocampal neurons evoked by long-term-potentiation-inducing electrical stimulation patterns

“…5). Because release of intracellular Ca 2ϩ is crucial for NT secretion, the temporal summation of Ca 2ϩ release from intracellular Ca 2ϩ stores may be a mechanism responsible for the fact that stimulation at high, but not low, frequencies results in BDNF secretion (46). The responsible Ca 2ϩ storage compartment, the smooth ER, is widely distributed throughout dendrites and axons including dendritic spines (47), which could explain the localization of NT6 secretion along axonal and dendritic processes (Fig.…”

Molecular Mechanisms of Ca2+ Signaling in Neurons Induced by the S100A4 Protein

“…The laser light intensity was reduced to 1 to 3% of the nominal intensity by using neutral filters to avoid photodamage of the cells and dye bleaching. Fluorescence intensity traces from individual neurons were obtained and processed as described previously (18). SPR analysis.…”

Early and Simultaneous Emergence of Multiple Hippocampal Biomarkers of Aging Is Mediated by Ca2+-Induced Ca2+Release

“…This protocol largely avoided spike failure, ensuring comparable levels of postsynaptic action potential generation throughout the train (Table 2), and mimicked physiologically relevant (theta) frequencies of synaptic activation. This RSS protocol causes significant Ca 2ϩ influx into the dendrites and somata of pyramidal neurons (Thibault et al, 2001), because repetitive spike generation triggers a large postsynaptic [Ca 2ϩ ] i response (Jaffe et al, 1992;Regehr and Tank, 1992;Brown and Jaffe, 1994;Helmchen et al, 1996;Jacobs and Meyer, 1997;Thibault et al, 2001). Figure 3A illustrates [Ca 2ϩ ] i responses obtained at rest and during peak [Ca 2ϩ ] i induced by RSS (inset; first 1 s) in representative CA1 neurons from a 4-month-old (top) and a 23-monthold (bottom) animal.…”