title: Reduced low-voltage activated K+ conductances and enhanced central excitability in a congenitally deaf (dn/dn) mouse.
abstract: We have investigated changes in the neuronal excitability of the auditory brainstem in a congenitally deaf mouse (deafness dn/dn). Whole cell patch recordings from principal neurones of the medial nucleus of the trapezoid body (MNTB) showed strikingly enhanced excitability in the deaf mice when compared to control CBA mice at 12-14 days postnatal. MNTB neurones in normal CBA mice showed the phenotypic single action potential response on depolarization in current clamp; however, recordings from CBA mice carrying the homozygous deafness mutation fired trains of action potentials on depolarization. We show here that these changes are associated with reduced functional expression of dendrotoxin-sensitive Kv1 potassium channels. In contrast, no differences were found in voltage-gated calcium currents between control and deaf mice. These results reveal that loss of hair cell function in the cochlea leads to changes in ion channel expression in the central nervous system and suggests that this deafness model will be an important tool in understanding central changes occurring in human congenital deafness and in exploring activity-dependent regulation of ion channel expression.
authors.affiliation: Synapse and Hearing Laboratory, Division of Neuroscience, John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, ACT 0200, Australia.
authors.forename: Richardson N
authors.initials: RN
authors.lastname: Leao
authors.forename: Amy
authors.initials: A
authors.lastname: Berntson
authors.forename: Ian D
authors.initials: ID
authors.lastname: Forsythe
authors.forename: Bruce
authors.initials: B
authors.lastname: Walmsley
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000503:physiopathology*; D003638:Deafness / Q000151:congenital* / Q000235:genetics* / Q000378:metabolism; D008564:Membrane Potentials / Q000235:genetics; D051379:Mice; D008808:Mice, Inbred CBA; D008818:Mice, Neurologic Mutants; D024642:Potassium Channels, Voltage-Gated / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics*
chemical_list: D024642:Potassium Channels, Voltage-Gated