title: Zonal variations in K+ currents in vestibular crista calyx terminals.
abstract: We developed a rodent crista slice to investigate regional variations in electrophysiological properties of vestibular afferent terminals. Thin transverse slices of the gerbil crista ampullaris were made and electrical properties of calyx terminals in central zones (CZ) and peripheral zones (PZ) compared with whole cell patch clamp. Spontaneous action potential firing was observed in 25% of current-clamp recordings and was either regular or irregular in both zones. Firing was abolished when extracellular choline replaced Na(+) but persisted when hair cell mechanotransduction channels or calyx AMPA receptors were blocked. This suggests that ion channels intrinsic to the calyx can generate spontaneous firing. In response to depolarizing voltage steps, outward K(+) currents were observed at potentials above -60 mV. K(+) currents in PZ calyces showed significantly more inactivation than currents in CZ calyces. Underlying K(+) channel populations contributing to these differences were investigated. The KCNQ channel blocker XE991 dihydrochloride blocked a slowly activating, sustained outward current in both PZ and CZ calyces, indicating the presence of KCNQ channels. Mean reduction was greatest in PZ calyces. XE991 also reduced action potential firing frequency in CZ and PZ calyces and broadened mean action potential width. The K(+) channel blocker 4-aminopyridine (10-50 μM) blocked rapidly activating, moderately inactivating currents that were more prevalent in PZ calyces. α-Dendrotoxin, a selective blocker of KV1 channels, reduced outward currents in CZ calyces but not in PZ calyces. Regional variations in K(+) conductances may contribute to different firing responses in calyx afferents.
authors.affiliation: Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado; and.
authors.forename: Frances L
authors.initials: FL
authors.lastname: Meredith
authors.affiliation: Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado; and Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado katie.rennie@ucdenver.edu.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Rennie
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism; D007758:Ear, Inner / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D004546:Elapid Venoms / Q000494:pharmacology; D005260:Female; D005849:Gerbillinae; D008297:Male; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D018091:Receptors, AMPA / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D046509:Tissue Culture Techniques
chemical_list: C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000873:Anthracenes; D004546:Elapid Venoms; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D018091:Receptors, AMPA; C020273:dendrotoxin; D012964:Sodium; D015761:4-Aminopyridine; D002794:Choline; D011188:Potassium
keywords: KCNQ; KV1; ganglion; hair cell; semicircular canal