title: KCNQ5 channels control resting properties and release probability of a synapse.
abstract: Little is known about which ion channels determine the resting electrical properties of presynaptic membranes. In recordings made from the rat calyx of Held, a giant mammalian terminal, we found resting potential to be controlled by KCNQ (Kv7) K(+) channels, most probably KCNQ5 (Kv7.5) homomers. Unlike most KCNQ channels, which are activated only by depolarizing stimuli, the presynaptic channels began to activate just below the resting potential. As a result, blockers and activators of KCNQ5 depolarized or hyperpolarized nerve terminals, respectively, markedly altering resting conductance. Moreover, the background conductance set by KCNQ5 channels, together with Na(+) and hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels, determined the size and time course of the response to subthreshold stimuli. Signaling pathways known to directly affect exocytic machinery also regulated KCNQ5 channels, and increase or decrease of KCNQ5 channel activity controlled release probability through alterations in resting potential. Thus, ion channel determinants of presynaptic resting potential also control synaptic strength.
authors.affiliation: Oregon Hearing Research Center, Oregon Health and Science University, Portland, Oregon, USA. huanghai@ohsu.edu
authors.forename: Hai
authors.initials: H
authors.lastname: Huang
authors.forename: Laurence O
authors.initials: LO
authors.lastname: Trussell
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000873:Anthracenes / Q000494:pharmacology; D001933:Brain Stem / Q000166:cytology; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000378:metabolism; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D066298:In Vitro Techniques; D051656:KCNQ Potassium Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology*; D018613:Microscopy, Confocal / Q000379:methods; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D017729:Presynaptic Terminals / Q000502:physiology*; D011336:Probability; D051381:Rats; D012604:Scorpion Venoms / Q000494:pharmacology; D013569:Synapses / Q000378:metabolism*
chemical_list: C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000873:Anthracenes; D054815:Cyclic Nucleotide-Gated Cation Channels; D004791:Enzyme Inhibitors; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D051656:KCNQ Potassium Channels; C501028:Kcnq5 protein, rat; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012604:Scorpion Venoms; C077910:margatoxin