title: Kv1 channels control spike threshold dynamics and spike timing in cortical pyramidal neurones.
abstract: Previous studies showed that cortical pyramidal neurones (PNs) have a dynamic spike threshold that functions as a high-pass filter, enhancing spike timing in response to high-frequency input. While it is commonly assumed that Na(+) channel inactivation is the primary mechanism of threshold accommodation, the possible role of K(+) channel activation in fast threshold changes has not been well characterized. The present study tested the hypothesis that low-voltage activated Kv1 channels affect threshold dynamics in layer 2-3 PNs, using α-dendrotoxin (DTX) or 4-aminopyridine (4-AP) to block these conductances. We found that Kv1 blockade reduced the dynamic changes of spike threshold in response to a variety of stimuli, including stimulus-evoked synaptic input, current steps and ramps of varied duration, and noise. Analysis of the responses to noise showed that Kv1 channels increased the coherence of spike output with high-frequency components of the stimulus. A simple model demonstrates that a dynamic spike threshold can account for this effect. Our results show that the Kv1 conductance is a major mechanism that contributes to the dynamic spike threshold and precise spike timing of cortical PNs.
authors.affiliation: Neurology Section, Department of Veterans Affairs Medical Centre, Seattle, WA 98108, USA. higgsm@uw.edu
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Higgs
authors.forename: William J
authors.initials: WJ
authors.lastname: Spain
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D004546:Elapid Venoms / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051637:Shaker Superfamily of Potassium Channels / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D004546:Elapid Venoms; D026902:Potassium Channel Blockers; D051637:Shaker Superfamily of Potassium Channels; C020273:dendrotoxin; D015761:4-Aminopyridine