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Dendritic Ca2+ Transients (dendritic + ca2+_transient)

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Life Sciences100%

Selected Abstracts

Dendritic nicotinic receptors modulate backpropagating action potentials and long-term plasticity of interneurons

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2008
Balázs Rózsa
Abstract Stratum radiatum interneurons, unlike pyramidal cells, are rich in nicotinic acetylcholine receptors (nAChRs); however, the role of these receptors in plasticity has remained elusive. As opposed to previous physiological studies, we found that functional ,7-subunit-containing nAChRs (,7-nAChRs) are abundant on interneuron dendrites of rats. Moreover, dendritic Ca2+ transients induced by activation of ,7-nAChRs increase as a function of distance from soma. The activation of these extrasynaptic ,7-nAChRs by cholinergic agonists either facilitated or depressed backpropagating action potentials, depending on the timing of ,7-nAChR activation. We have previously shown that dendritic ,7-nAChRs are involved in the regulation of synaptic transmission, suggesting that ,7-nAChRs may play an important role in the regulation of the spike timing-dependent plasticity. Here we provide evidence that long-term potentiation is indeed boosted by stimulation of dendritic ,7-nAChRs. Our results suggest a new mechanism for a cholinergic switch in memory encoding and retrieval. [source]

Cellular and subcellular localization of the neuron-specific plasma membrane calcium ATPase PMCA1a in the rat brain

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 16 2010
Katharine A. Kenyon
Abstract Regulation of intracellular calcium is crucial both for proper neuronal function and survival. By coupling ATP hydrolysis with Ca2+ extrusion from the cell, the plasma membrane calcium-dependent ATPases (PMCAs) play an essential role in controlling intracellular calcium levels in neurons. In contrast to PMCA2 and PMCA3, which are expressed in significant levels only in the brain and a few other tissues, PMCA1 is ubiquitously distributed, and is thus widely believed to play a "housekeeping" function in mammalian cells. Whereas the PMCA1b splice variant is predominant in most tissues, an alternative variant, PMCA1a, is the major form of PMCA1 in the adult brain. Here, we use immunohistochemistry to analyze the cellular and subcellular distribution of PMCA1a in the brain. We show that PMCA1a is not ubiquitously expressed, but rather is confined to neurons, where it concentrates in the plasma membrane of somata, dendrites, and spines. Thus, rather than serving a general housekeeping function, our data suggest that PMCA1a is a calcium pump specialized for neurons, where it may contribute to the modulation of somatic and dendritic Ca2+ transients. J. Comp. Neurol. 518:3169,3183, 2010. © 2010 Wiley-Liss, Inc. [source]

Cellular and subcellular localization of the neuron-specific plasma membrane calcium ATPase PMCA1a in the rat brain

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 16 2010
Katharine A. Kenyon
Abstract Regulation of intracellular calcium is crucial both for proper neuronal function and survival. By coupling ATP hydrolysis with Ca2+ extrusion from the cell, the plasma membrane calcium-dependent ATPases (PMCAs) play an essential role in controlling intracellular calcium levels in neurons. In contrast to PMCA2 and PMCA3, which are expressed in significant levels only in the brain and a few other tissues, PMCA1 is ubiquitously distributed, and is thus widely believed to play a "housekeeping" function in mammalian cells. Whereas the PMCA1b splice variant is predominant in most tissues, an alternative variant, PMCA1a, is the major form of PMCA1 in the adult brain. Here, we use immunohistochemistry to analyze the cellular and subcellular distribution of PMCA1a in the brain. We show that PMCA1a is not ubiquitously expressed, but rather is confined to neurons, where it concentrates in the plasma membrane of somata, dendrites, and spines. Thus, rather than serving a general housekeeping function, our data suggest that PMCA1a is a calcium pump specialized for neurons, where it may contribute to the modulation of somatic and dendritic Ca2+ transients. J. Comp. Neurol. 518:3169,3183, 2010. © 2010 Wiley-Liss, Inc. [source]

Efficient Ca2+ buffering in fast-spiking basket cells of rat hippocampus

THE JOURNAL OF PHYSIOLOGY, Issue 8 2008
Yexica Aponte
Fast-spiking parvalbumin-expressing basket cells (BCs) represent a major type of inhibitory interneuron in the hippocampus. These cells inhibit principal cells in a temporally precise manner and are involved in the generation of network oscillations. Although BCs show a unique expression profile of Ca2+ -permeable receptors, Ca2+ -binding proteins and Ca2+ -dependent signalling molecules, physiological Ca2+ signalling in these interneurons has not been investigated. To study action potential (AP)-induced dendritic Ca2+ influx and buffering, we combined whole-cell patch-clamp recordings with ratiometric Ca2+ imaging from the proximal apical dendrites of rigorously identified BCs in acute slices, using the high-affinity Ca2+ indicator fura-2 or the low-affinity dye fura-FF. Single APs evoked dendritic Ca2+ transients with small amplitude. Bursts of APs evoked Ca2+ transients with amplitudes that increased linearly with AP number. Analysis of Ca2+ transients under steady-state conditions with different fura-2 concentrations and during loading with 200 ,m fura-2 indicated that the endogenous Ca2+ -binding ratio was ,200 (,S= 202 ± 26 for the loading experiments). The peak amplitude of the Ca2+ transients measured directly with 100 ,m fura-FF was 39 nm AP,1. At ,23°C, the decay time constant of the Ca2+ transients was 390 ms, corresponding to an extrusion rate of ,600 s,1. At 34°C, the decay time constant was 203 ms and the corresponding extrusion rate was ,1100 s,1. At both temperatures, continuous theta-burst activity with three to five APs per theta cycle, as occurs in vivo during exploration, led to a moderate increase in the global Ca2+ concentration that was proportional to AP number, whereas more intense stimulation was required to reach micromolar Ca2+ concentrations and to shift Ca2+ signalling into a non-linear regime. In conclusion, dentate gyrus BCs show a high endogenous Ca2+ -binding ratio, a small AP-induced dendritic Ca2+ influx, and a relatively slow Ca2+ extrusion. These specific buffering properties of BCs will sharpen the time course of local Ca2+ signals, while prolonging the decay of global Ca2+ signals. [source]