Kv3 K+ channels enable burst output in rat cerebellar Purkinje cells.
The ability of cells to generate an appropriate spike output depends on a balance between membrane depolarizations and the repolarizing actions of K(+) currents. The high-voltage-activated Kv3 class of K(+) channels repolarizes Na(+) spikes to maintain high frequencies of discharge. However, little is known of the ability for these K(+) channels to shape Ca(2+) spike discharge or their ability to regulate Ca(2+) spike-dependent burst output. Here we identify the role of Kv3 K(+) channels in the regulation of Na(+) and Ca(2+) spike discharge, as well as burst output, using somatic and dendritic recordings in rat cerebellar Purkinje cells. Kv3 currents pharmacologically isolated in outside-out somatic membrane patches accounted for approximately 40% of the total K(+) current, were very fast and high voltage activating, and required more than 1 s to fully inactivate. Kv3 currents were differentiated from other tetraethylammonium-sensitive currents to establish their role in Purkinje cells under physiological conditions with current-clamp recordings. Dual somatic-dendritic recordings indicated that Kv3 channels repolarize Na(+) and Ca(2+) spikes, enabling high-frequency discharge for both types of cell output. We further show that during burst output Kv3 channels act together with large-conductance Ca(2+)-activated K(+) channels to ensure an effective coupling between Ca(2+) and Na(+) spike discharge by preventing Na(+) spike inactivation. By contributing significantly to the repolarization of Na(+) and especially Ca(2+) spikes, our data reveal a novel function for Kv3 K(+) channels in the maintenance of high-frequency burst output for cerebellar Purkinje cells.
McKay
B E
BE
Neuroscience Research Group, University of Calgary, Calgary, Alberta, Canada T2N 4 N1.
Turner
R W
RW
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004546:Elapid Venoms / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D066298:In Vitro Techniques; D008297:Male; D018408:Patch-Clamp Techniques / Q000379:methods; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D051670:Shaw Potassium Channels; D012964:Sodium / Q000378:metabolism; D026941:Sodium Channel Blockers / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D004546:Elapid Venoms; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051670:Shaw Potassium Channels; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; D019789:Tetraethylammonium; C020273:dendrotoxin; C064719:iberiotoxin; D012964:Sodium; D002118:Calcium