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

细胞内钙离子在各种组织的细胞功能中起着重要的作用。在螺旋神经节细胞中，神经递质的释放依赖于细胞内钙离子通过电压依赖性钙通道的反应。我们检测了卡那霉素中毒豚鼠螺旋神经节细胞去极化引起的胞浆Ca~(2+)-Gt~(2+)反应，以评价病理状态下膜通道的活动。以未经治疗的豚鼠为对照。对照组豚鼠ABR反应正常。另一方面，卡那霉素中毒的豚鼠在65dBSPL以下对短声诱发的反应不明显。机械分离豚鼠耳蜗螺旋神经节细胞。在激光扫描显微镜下，用Fluo-3/Fura-Red比率法检测细胞内钙离子浓度的动态变化。高K+引起的去极化使神经节细胞胞内Ca~(2+)&Gt~(2+)浓度升高，细胞内Ca~(2+)-Gt~(2+)浓度升高。部分细胞胞浆Ca~(2+)水平呈振荡性升高。此外，损伤的螺旋神经节细胞对去极化引起的胞浆Ca~(2+)-Gt~(2+)反应较对照细胞降低。

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.