Walter Marcotti

Learn More
Hair cells in mouse cochlear cultures are selectively labeled by brief exposure to FM1-43, a styryl dye used to study endocytosis and exocytosis. Real-time confocal microscopy indicates that dye entry is rapid and via the apical surface. Cooling to 4 degrees C and high extracellular calcium both reduce dye loading. Pretreatment with EGTA, a condition that(More)
Developmental changes in electrophysiological membrane properties of mouse cochlear inner hair cells (IHCs) were studied from just after terminal differentiation up to functional maturity. As early as embryonic day 14.5 (E14.5) newly differentiated IHCs express a very small outward K+ current that is largely insensitive to 4-aminopyridine (4-AP). One day(More)
Developmental changes in the coupling between Ca2+ entry and exocytosis were studied in mouse inner hair cells (IHCs) which, together with the afferent endings, form the primary synapse of the mammalian auditory system. Ca2+ currents (ICa) and changes in membrane capacitance (DeltaCm) were recorded using whole-cell voltage clamp from cells maintained at(More)
1. The expression of K+ currents in mouse outer hair cells (OHCs) was investigated as a function of developmental age between postnatal day (P) 0 and P26, using whole-cell patch clamp. 2. During the first postnatal week, a slow outward K+ current (IK,neo) was expressed by all OHCs from the apical coil of the cochlea. The amplitude of this current increased(More)
Before the onset of hearing at postnatal day 12, mouse inner hair cells (IHCs) produce spontaneous and evoked action potentials. These spikes are likely to induce neurotransmitter release onto auditory nerve fibres. Since immature IHCs express both alpha1D (Cav1.3) Ca2+ and Na+ currents that activate near the resting potential, we examined whether these two(More)
The most serious side-effect of the widely used aminoglycoside antibiotics is irreversible intracellular damage to the auditory and vestibular hair cells of the inner ear. The mechanism of entry into the hair cells has not been unequivocally resolved. Here we report that extracellular dihydrostreptomycin not only blocks the mechano-electrical transducer(More)
The hair bundles of outer hair cells in the mature mouse cochlea possess three distinct cell-surface specializations: tip links, horizontal top connectors, and tectorial membrane attachment crowns. Electron microscopy was used to study the appearance and maturation of these link types and examine additional structures transiently associated with the(More)
Inwardly rectifying K+ currents in inner and outer hair cells (IHCs, OHCs) were studied during postnatal development of the mouse cochlea. Hyperpolarizing steps from a holding potential of –64 mV induced a rapidly activating current in both cell types. This current showed strong inward rectification around the K+ equilibrium potential and, at potentials(More)
Mutations in Myo7a cause hereditary deafness in mice and humans. We describe the effects of two mutations, Myo7a(6J) and Myo7a(4626SB), on mechano-electrical transduction in cochlear hair cells. Both mutations result in two major functional abnormalities that would interfere with sound transduction. The hair bundles need to be displaced beyond their(More)
From just after birth, mouse inner hair cells (IHCs) expressed a Ca(2+)-activated K(+) current that was reduced by intracellular BAPTA at concentrations >or= 1 mM. The block of this current by nifedipine suggests the direct involvement of Ca(v)1.3 Ca(2+) channels in its activation. On the basis of its high sensitivity to apamin (K(D) 360 pM) it was(More)