title: Properties and functional implications of I                      (h) in hippocampal area CA3 interneurons.
abstract: The present study examines the biophysical properties and functional implications of I                         (h) in hippocampal area CA3 interneurons with somata in strata radiatum and lacunosum-moleculare. Characterization studies showed a small maximum h-conductance (2.6 ± 0.3 nS, n = 11), shallow voltage dependence with a hyperpolarized half-maximal activation (V                         (1/2) = -91 mV), and kinetics characterized by double-exponential functions. The functional consequences of I                         (h) were examined with regard to temporal summation and impedance measurements. For temporal summation experiments, 5-pulse mossy fiber input trains were activated. Blocking I                         (h) with 50 μM ZD7288 resulted in an increase in temporal summation, suggesting that I                         (h) supports sensitivity of response amplitude to relative input timing. Impedance was assessed by applying sinusoidal current commands. From impedance measurements, we found that I                         (h) did not confer theta-band resonance, but flattened the impedance-frequency relations instead. Double immunolabeling for hyperpolarization-activated cyclic nucleotide-gated proteins and glutamate decarboxylase 67 suggests that all four subunits are present in GABAergic interneurons from the strata considered for electrophysiological studies. Finally, a model of I                         (h) was employed in computational analyses to confirm and elaborate upon the contributions of I                         (h) to impedance and temporal summation.
authors.affiliation: Department of Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, PA 15260, USA.
authors.forename: Warren D
authors.initials: WD
authors.lastname: Anderson
authors.forename: Emilio J
authors.initials: EJ
authors.lastname: Galván
authors.forename: Jocelyn C
authors.initials: JC
authors.lastname: Mauna
authors.forename: Edda
authors.initials: E
authors.lastname: Thiels
authors.forename: Germán
authors.initials: G
authors.lastname: Barrionuevo
mesh_terms: D000818:Animals; D003198:Computer Simulation; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007395:Interneurons / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015221:Potassium Channels; D021122:Protein Subunits; D005680:gamma-Aminobutyric Acid