title: Region-specific regulation of voltage-gated intrinsic currents in the developing optic tectum of the Xenopus tadpole.
abstract: Across the rostrocaudal (RC) axis of the Xenopus tadpole optic tectum exists a developmental gradient. This gradient has served as a useful model to study many aspects of synapse and dendrite maturation. To compliment these studies, we characterized how the intrinsic excitability, the ease in which a neuron can fire action potentials, might also be changing across the same axis. Whole-cell recordings from tectal neurons at different points along the RC axis revealed a graded increase in intrinsic excitability: compared with neurons at the caudal end of the tectum, neurons at the rostral end fired more action potentials in response to current injection and expressed greater peak Na⁺ and K⁺ currents, the major intrinsic currents in these neurons that underlie the action potential. We also observed, along the same axis and in the same direction, a previously described increase in the amount of synaptic drive received by individual neurons (Wu GY, Malinow R, Cline HT. Science 274: 972-976, 1996). Thus as synaptic activity ramps up across the RC axis, so does intrinsic excitability. The reduction of overall circuit activity induced a compensatory scaling up of peak Na⁺ and K⁺ currents only in the caudal portion of the tectum, suggesting a region-specific, compensatory form of plasticity.
authors.affiliation: Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming.
authors.forename: Ali S
authors.initials: AS
authors.lastname: Hamodi
authors.affiliation: Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming kpratt4@uwyo.edu.
authors.forename: Kara G
authors.initials: KG
authors.lastname: Pratt
mesh_terms: D000200:Action Potentials; D000818:Animals; D019706:Excitatory Postsynaptic Potentials; D009474:Neurons / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology; D013477:Superior Colliculi / Q000254:growth & development*; D061566:Voltage-Gated Sodium Channels / Q000502:physiology; D014981:Xenopus
chemical_list: D024642:Potassium Channels, Voltage-Gated; D061566:Voltage-Gated Sodium Channels
keywords: Xenopus tadpole; development; instrinsic currents; optic tectum; region specific