![]() ![]() 74, 1810–1814 (1995).īuzsaki, G., Penttonen, M., Nadasdy, Z. APs that back-propagate into the apical dendrite have been shown to cause Ca2+ influx in pyramidal neurons (1, 68). One unique neuronal compartment associated with calcium homeostasis is the dendritic spine, the site of excitatory synapses in the majority of neurons in the brain. As second messenger of many signaling pathways, Ca 2+ as been shown to regulate neuronal gene expression, energy production, membrane excitability, synaptogenesis, synaptic transmission, and other processes underlying learning and memory and cell survival. 4, 436–439 (1994).ĭenk, W., Strickler, J. Indeed, recent studies have detected the presence of Orai1 channels in central neurons, 1,2 and further studies indicated that STIM2, the sensor for endoplasmic reticulum calcium store depletion, is instrumental in maintenance of mature dendritic spines in cultured hippocampal neurons. Calcium (Ca 2+) plays fundamental and diversified roles in neuronal plasticity. This suggests that widespread Ca 2+ action potentials were not generated, and any significant increase depends on somatically triggered Na + action potentials. The amplitude for a given number of action potentials was greatest in the proximal apical dendrite and declined steeply with increasing distance from the soma, with little Ca 2+ accumulation in the most distal branches, in layer 1. Calcium Signaling and the Control of Dendritic Development Dendrites serve a critical role in neuronal information processing as sites of synaptic integration. The amplitude of these transients at a given location was approximately proportional to the number of Na + action potentials in a short burst. Simultaneous recordings of intracellular voltage and dendritic dynamics during whisker stimulation or current injection showed increases in only in coincidence with Na + action potentials. We used this property to measure sensory stimulus-induced dendritic dynamics of layer 2/3 pyramidal neurons of the rat primary vibrissa (Sm1) cortex in vivo. Here we show that two-photon excitation laser scanning microscopy 3 can penetrate the highly scattering tissue of the intact brain. This makes it difficult to extrapolate from in vitro experiments to the situation in the intact brain. The presence, site of initiation, and direction of propagation of Na + and Ca 2+ action potentials are, however, controversial 2, and seem to be sensitive to resting membrane potential, ionic composition, and degree of channel inactivation, and depend on the intensity and pattern of synaptic stimulation. THE dendrites of mammalian pyramidal neurons contain a rich collection of active conductances that can support Na + and Ca 2+ action potentials (for a review see ref. ![]()
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