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The Journal of Neuroscience, October 1, 1999, 19(19):8319-8326

Dendritic Ca²⁺-Activated K⁺ Conductances Regulate Electrical Signal Propagation in an Invertebrate Neuron

Ralf Wessel¹, William B. Kristan Jr², and David Kleinfeld¹

Departments of ¹ Physics and ² Biology, University of California at San Diego, La Jolla, California 92093

Activity-dependent changes in the short-term electrical properties of neurites were investigated in the anterior pagoda (AP) cell of leech. Imaging studies revealed that backpropagating Na⁺ spikes and synaptically evoked EPSPs caused Ca²⁺ entry through low-voltage-activated Ca²⁺ channels that are distributed throughout the neurites. Voltage-clamp recordings from the soma revealed a TEA-sensitive outward current that was reduced when Ca²⁺ entry was blocked with Co²⁺ or when the intracellular concentration of free Ca²⁺ was reduced by a high-affinity Ca²⁺ buffer. Ca²⁺ released in the neurite from a caged Ca²⁺ compound caused a hyperpolarization of the membrane potential. These data imply that the AP cell expresses Ca²⁺-activated K⁺ conductances, and that these conductances are present in the neurites. When the Ca²⁺-activated K⁺ current was reduced through the block of Ca²⁺ entry, backpropagating Na⁺ spikes and synaptically evoked EPSPs increased in amplitude. Hence, the activity-dependent changes in the intracellular [Ca²⁺] together with the Ca²⁺-activated K⁺ conductances participate in the regulation of dendritic signal propagation.

Key words: calcium; dendrite; calcium-activated potassium conductance; backpropagating spikes; caged calcium; leech

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Copyright © 1999 Society for Neuroscience  0270-6474/99/19198319-08$05.00/0

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