title: Preliminary characterization of voltage-activated whole-cell currents in developing human vestibular hair cells and calyx afferent terminals.
abstract: We present preliminary functional data from human vestibular hair cells and primary afferent calyx terminals during fetal development. Whole-cell recordings were obtained from hair cells or calyx terminals in semi-intact cristae prepared from human fetuses aged between 11 and 18 weeks gestation (WG). During early fetal development (11-14 WG), hair cells expressed whole-cell conductances that were qualitatively similar but quantitatively smaller than those observed previously in mature rodent type II hair cells. As development progressed (15-18 WG), peak outward conductances increased in putative type II hair cells but did not reach amplitudes observed in adult human hair cells. Type I hair cells express a specific low-voltage activating conductance, G K,L. A similar current was first observed at 15 WG but remained relatively small, even at 18 WG. The presence of a "collapsing" tail current indicates a maturing type I hair cell phenotype and suggests the presence of a surrounding calyx afferent terminal. We were also able to record from calyx afferent terminals in 15-18 WG cristae. In voltage clamp, these terminals exhibited fast inactivating inward as well as slower outward conductances, and in current clamp, discharged a single action potential during depolarizing steps. Together, these data suggest the major functional characteristics of type I and type II hair cells and calyx terminals are present by 18 WG. Our study also describes a new preparation for the functional investigation of key events that occur during maturation of human vestibular organs.
authors.affiliation: The School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Hunter Medical Research Institute, The University of Newcastle, Callaghan, NSW, 2308, Australia, Rebecca.Lim@newcastle.edu.au.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Lim
authors.forename: Hannah R
authors.initials: HR
authors.lastname: Drury
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Camp
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Tadros
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Callister
authors.forename: Alan M
authors.initials: AM
authors.lastname: Brichta
mesh_terms: D000344:Afferent Pathways / Q000502:physiology*; D047109:Fetal Development; D018069:Hair Cells, Vestibular / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials