Cell Biotechnology and Molecular Biology of the Isolated Spiral Ganglion Cells in the Ear with Profound Hearing Loss

细胞内Ca^<2+>在各种组织的细胞功能中起重要作用。在螺旋神经节细胞中，已知神经递质释放依赖于通过电压依赖性Ca^<2+>通道的胞质Ca^<2+>反应。我们检测了卡那霉素中毒豚鼠离体螺旋神经节细胞去极化诱导的胞质Ca^<2+>反应，以评价病理条件下Ca^<2+>通道的活性。白化病豚鼠（体重250-250g）肌肉注射克那霉素400 mg/次，每周5次，连续3周。未处理的豚鼠作为对照。对照豚鼠ABR反应正常。另一方面，卡那霉素中毒的豚鼠在点击诱发的65 dB SPL以下没有可检测到的反应。机械分离豚鼠耳蜗螺旋神经节细胞。在激光扫描显微镜下，采用Fluo-3/Fura-Red比率法估计细胞内Ca^<2+>浓度的动态变化。Ca^<2+>通道的激活是通过高K+诱导退极化获得的。高K+诱导的脱离作用使神经节细胞胞浆Ca^<2+>浓度升高。部分细胞胞浆Ca^<2+>水平振荡性升高。此外，与对照细胞相比，受损螺旋神经节细胞去极化诱导的细胞solicca ^<2+>反应降低。

Intracellular Ca^<2+> plays an important role in the cellular functions of various tissues. In the spiral ganglion cells, neurotransmitter release is known to be dependent on cytosolic Ca^<2+> responses through voltage-dependent Ca^<2+> channels. We examined cytosolic Ca^<2+> responses induced by depolarization in the isolated spiral ganglion cells of the kanamycin-intoxicated guinea-pig to evaluate the activity of theCa^<2+> channel in pathological conditions.Albino guinea-pigs (weight 250-250g) received intramuscular injections of 400 mg/kgkanamycin 5 times per week for 3 weeks. Guinea pigs without treatment were used as controls. Control guinea-pigs showed normal ABR responses. On the other hand, kanamycin-intoxicatedguinea pigs showed no detectable responses below 65 dB SPL evoked by click. Spiral ganglion cells of the guinea-pig cochlea were mechanically isolated. Dynamic changes in intracellular Ca^<2+>concentration were estimated with Fluo-3/Fura-Red ratiometric method using a LASER-scanning microscope. Activation of the Ca^<2+> channel was obtained by high K+-induced depolarization.High K+-induced deporalization elevated the cytosolic Ca^<2+> concentration of the ganglion cells. Some of the cells showed oscillatory increases in the cytosolic Ca^<2+> level. Furthermore, the cytosolicCa^<2+> response induced by depolarization was decreased in damaged spiral ganglion cells compared with that in control cells.