Dendritic Ca(2+)-activated K(+) conductances regulate electrical signal propagation in an invertebrate neuron.
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 Ca(2+) entry through low-voltage-activated Ca(2+) channels that are distributed throughout the neurites. Voltage-clamp recordings from the soma revealed a TEA-sensitive outward current that was reduced when Ca(2+) entry was blocked with Co(2+) or when the intracellular concentration of free Ca(2+) was reduced by a high-affinity Ca(2+) buffer. Ca(2+) released in the neurite from a caged Ca(2+) compound caused a hyperpolarization of the membrane potential. These data imply that the AP cell expresses Ca(2+)-activated K(+) conductances, and that these conductances are present in the neurites. When the Ca(2+)-activated K(+) current was reduced through the block of Ca(2+) entry, backpropagating Na(+) spikes and synaptically evoked EPSPs increased in amplitude. Hence, the activity-dependent changes in the intracellular [Ca(2+)] together with the Ca(2+)-activated K(+) conductances participate in the regulation of dendritic signal propagation.
Wessel
R
R
Department of Physics, University of California at San Diego, La Jolla, California 92093, USA.
Kristan
W B
WB
Kleinfeld
D
D
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D003035:Cobalt / Q000494:pharmacology; D003712:Dendrites / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D007865:Leeches; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D016501:Neurites / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction; D012964:Sodium / Q000494:pharmacology
D015220:Calcium Channels; D015221:Potassium Channels; D003035:Cobalt; D012964:Sodium; D002118:Calcium