Hepatocyte Growth Factor-c-MET Signaling Mediates the Development of Nonsensory Structures of the Mammalian Cochlea and Hearing.

Unlabelled: The stria vascularis is a nonsensory structure that is essential for auditory hair cell function by maintaining potassium concentration of the scala media. During mouse embryonic development, a subpopulation of neural crest cell-derived melanocytes migrates and incorporates into a subregion of the cochlear epithelium, forming the intermediate cell layer of the stria vascularis. The relation of this developmental process to stria vascularis function is currently unknown.

Fgf10 is required for specification of non-sensory regions of the cochlear epithelium.

The vertebrate inner ear is a morphologically complex sensory organ comprised of two compartments, the dorsal vestibular apparatus and the ventral cochlear duct, required for motion and sound detection, respectively. Fgf10, in addition to Fgf3, is necessary for the earliest stage of otic placode induction, but continued expression of Fgf10 in the developing otic epithelium, including the prosensory domain and later in Kolliker׳s organ, suggests additional roles for this gene during morphogenesis of the labyrinth. While loss of Fgf10 was implicated previously in semicircular canal agenesis, we show that Fgf10(-/+) embryos also exhibit a reduction or absence of the posterior semicircular canal, revealing a dosage-sensitive requirement for FGF10 in vestibular development.

Bilirubin potentiates inhibitory synaptic transmission in lateral superior olive neurons of the rat.

Bilirubin is a well-known neurotoxin that can result in multiple neurologic deficits. Previous studies have suggested that bilirubin affects aspects of synaptic transmission; however the acute effects of bilirubin on synaptic transmission have not been examined in real-time. In this study, using whole-cell voltage-clamp recordings, we observed the effect of bilirubin on inhibitory postsynaptic currents (IPSC) in postnatal 13-15-day-old neurons dissociated from lateral superior olive nuclei (LSO), one of the brainstem auditory nucleus that are highly vulnerable to bilirubin.

Squamous cell carcinoma of the external auditory canal and middle ear: an operation combined with preoperative chemoradiotherapy and a free surgical margin.

Objective: Treatment outcomes for squamous cell carcinoma of the temporal bone were evaluated regarding stage, therapeutic strategy, and prognostic factors.

Study Design: Retrospective case review.

Setting: University hospital and outpatient clinic.

GABA-induced response in spiral ganglion cells acutely isolated from guinea pig cochlea.

The physiological and pharmacological properties of gamma-aminobutyric acid (GABA)-induced responses were investigated in acutely isolated spiral ganglion cells (SGCs) of guinea pig by using either a nystatin-perforated patch recording configuration or a conventional whole-cell patch recording mode combined with rapid drug application. GABA and GABA(A) subtype receptor agonist, muscimol, induced inward currents in a concentration-dependent manner in 74% of all cells. The current-voltage relationship for the GABA response indicated the GABA-induced current in SGCs is carried by Cl-.

Experience-dependent changes in intracellular Cl- regulation in developing auditory neurons.

A developmental change in GABA and glycine responses, from a depolarization to a hyperpolarization, have been reported for a range of CNS neurons, and has been demonstrated to be due to a developmental decrease in the intracellular Cl- concentration ([Cl-](i)). We examined [Cl-](i) in isolated rat lateral superior olive (LSO) neurons using patch-clamp recordings of glycine gated Cl- currents and by measuring intracellular Cl- -fluorescence. In neurons from 14-16-day-old rats (P14-P16), which had previously received unilateral or bilateral cochlear ablations before the onset of hearing, there was no developmental decrease in [Cl-](i).

Developmental switch from GABA to glycine release in single central synaptic terminals.

Early in postnatal development, inhibitory inputs to rat lateral superior olive (LSO) neurons change from releasing predominantly GABA to releasing predominantly glycine into the synapse. Here we show that spontaneous miniature inhibitory postsynaptic currents (mIPSCs) also change from GABAergic to glycinergic over the first two postnatal weeks. Many 'mixed' mIPSCs, resulting from co-release of glycine and GABA from the same vesicles, are seen during this transition.