title: Hyperpolarization-activated cyclic nucleotide-gated cation channels regulate auditory coincidence detection in nucleus laminaris of the chick.
abstract: Coincidence detection of bilateral acoustic signals in nucleus laminaris (NL) is the first step in azimuthal sound source localization in birds. Here, we demonstrate graded expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels along the tonotopic axis of NL and its role in the regulation of coincidence detection. Expression of HCN1 and HCN2, but not HCN3 or HCN4, was detected in NL. Based on measurement of both subtype mRNA and protein, HCN1 varied along the tonotopic axis and was minimal in high-characteristic frequency (CF) neurons. In contrast, HCN2 was evenly distributed. The resting conductance was larger and the steady-state activation curve of Ih was more positive in neurons of middle to low CF than those of high CF, consistent with the predominance of HCN1 channels in these neurons. Application of 8-Br-cAMP or noradrenaline generated a depolarizing shift of the Ih voltage activation curve. This shift was larger in neurons of high CF than in those of middle CF. The shift in the activation voltage of Ih depolarized the resting membrane, accelerated the EPSP time course, and significantly improved the coincidence detection in neurons of high CF, suggesting that Ih may improve the localization of sound sources.
authors.affiliation: Department of Physiology, Faculty of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Rei
authors.initials: R
authors.lastname: Yamada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuba
authors.forename: Takahiro M
authors.initials: TM
authors.lastname: Ishii
authors.forename: Harunori
authors.initials: H
authors.lastname: Ohmori
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001306:Auditory Pathways / Q000378:metabolism / Q000502:physiology*; D002645:Chickens; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels; D004553:Electric Conductivity; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007150:Immunohistochemistry; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials; D009475:Neurons, Afferent / Q000378:metabolism / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D009712:Nucleotides, Cyclic / Q000502:physiology*; D010782:Photolysis; D015221:Potassium Channels; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011930:Reaction Time; D013017:Sound Localization / Q000502:physiology*; D013997:Time Factors
chemical_list: C089981:(2-nitrophenyl)ethyl-cyclic adenosine monophosphate; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D009712:Nucleotides, Cyclic; D015221:Potassium Channels; D020033:Protein Isoforms; D012333:RNA, Messenger; D000242:Cyclic AMP; D009638:Norepinephrine