A dynamic dendritic refractory period regulates burst discharge in the electrosensory lobe of weakly electric fish.
Na+-dependent spikes initiate in the soma or axon hillock region and actively backpropagate into the dendritic arbor of many central neurons. Inward currents underlying spike discharge are offset by outward K+ currents that repolarize a spike and establish a refractory period to temporarily prevent spike discharge. We show in a sensory neuron that somatic and dendritic K+ channels differentially control burst discharge by regulating the extent to which backpropagating dendritic spikes can re-excite the soma. During repetitive discharge a progressive broadening of dendritic spikes promotes a dynamic increase in dendritic spike refractory period. A leaky integrate-and-fire model shows that spike bursts are terminated when a decreasing somatic interspike interval and an increasing dendritic spike refractory period synergistically act to block backpropagation. The time required for the somatic interspike interval to intersect with dendritic refractory period determines burst frequency, a time that is regulated by somatic and dendritic spike repolarization. Thus, K+ channels involved in spike repolarization can efficiently control the pattern of spike output by establishing a soma-dendritic interaction that invokes dynamic shifts in dendritic spike properties.
Noonan
Liza
L
Neuroscience Research Group, University of Calgary, Calgary, Alberta, Canada T2N 4N1. rwturner@ucalgary.ca
Doiron
Brent
B
Laing
Carlo
C
Longtin
Andre
A
Turner
Ray W
RW
D000200:Action Potentials; D000818:Animals; D002478:Cells, Cultured; D003712:Dendrites / Q000502:physiology*; D004553:Electric Conductivity; D023702:Gymnotiformes; D007700:Kinetics; D015221:Potassium Channels / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology*; D012032:Refractory Period, Electrophysiological
D015221:Potassium Channels