Figure 4.
Sodium salicylate increases Glu response of cochlear spiral ganglion neurons. A, Voltage- and current-clamp measurements were performed on cochlear spiral ganglion neuron somata from cochlear slices of neonate rat (scale bar, 500 μm). m, Modiolus; SM, scala media; ST, scala tympani; SV, scala vestibule. B, This preparation allows a clear view of the IHCs and OHCs and the cochlear spiral ganglion neurons. Scale bar, 20 μm. Top inset, Confocal immunolocalization of hair cells (red, rhodamine phalloidin) and nerve terminals (green, neurofilament). Scale bar, 150 μm. Bottom inset, Recording and drug delivery pipettes. Scale bar, 20 μm. bm, Basilar membrane; tm, tectorial membrane. C, D, Shown are voltage- and current-clamp recordings from cochlear spiral ganglion neuron somata after application of 5 mm NaSal alone, 1 mm Glu alone, 1 mm Glu with 5 mm NaSal in the bath, and after Glu with NaSal plus 50 μm MK-801. Although application of NaSal alone had no effect, it dramatically increases the Glu-induced currents and voltage response. Coapplication of 50 μm MK-801 prevented augmentation of the Glu response. E, F, Quantification of currents and voltage variations. Each bar represents the amplitude of currents and membrane potentials. The number of cells is given above each bar. Data are expressed as mean ± SEM. *p < 0.01, statistically significant from Glu alone.