title: Small-conductance Ca2+-activated K+ channels modulate action potential-induced Ca2+ transients in hippocampal neurons.
abstract: In hippocampal pyramidal neurons, voltage-gated Ca(2+) channels open in response to action potentials. This results in elevations in the intracellular concentration of Ca(2+) that are maximal in the proximal apical dendrites and decrease rapidly with distance from the soma. The control of these action potential-evoked Ca(2+) elevations is critical for the regulation of hippocampal neuronal activity. As part of Ca(2+) signaling microdomains, small-conductance Ca(2+)-activated K(+) (SK) channels have been shown to modulate the amplitude and duration of intracellular Ca(2+) signals by feedback regulation of synaptically activated Ca(2+) sources in small distal dendrites and dendritic spines, thus affecting synaptic plasticity in the hippocampus. In this study, we investigated the effect of the activation of SK channels on Ca(2+) transients specifically induced by action potentials in the proximal processes of hippocampal pyramidal neurons. Our results, obtained by using selective SK channel blockers and enhancers, show that SK channels act in a feedback loop, in which their activation by Ca(2+) entering mainly through L-type voltage-gated Ca(2+) channels leads to a reduction in the subsequent dendritic influx of Ca(2+). This underscores a new role of SK channels in the proximal apical dendrite of hippocampal pyramidal neurons.
authors.affiliation: Research Dept. of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, UK.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Tonini
authors.forename: Teresa
authors.initials: T
authors.lastname: Ferraro
authors.forename: Marisol
authors.initials: M
authors.lastname: Sampedro-Castañeda
authors.forename: Anna
authors.initials: A
authors.lastname: Cavaccini
authors.forename: Martin
authors.initials: M
authors.lastname: Stocker
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Richards
authors.forename: Paola
authors.initials: P
authors.lastname: Pedarzani
mesh_terms: D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling; D025461:Feedback, Physiological; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017966:Pyramidal Cells / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; D026902:Potassium Channel Blockers; D051640:Small-Conductance Calcium-Activated Potassium Channels; D002118:Calcium