Drescher M J, Drescher D G, Hatfield J S
Brain Res. 1987 Aug 4;417(1):39-50. doi: 10.1016/0006-8993(87)90177-6.
An in vitro preparation of the trout saccular macula, containing a large number of hair cells, served as a potential source of neurotransmitter(s) released at the acousticolateralis hair cell-afferent nerve synapse. An in vitro preparation of the saccular nerve, maintained in parallel, served to indicate the potential neural contribution to overall release from the macula. Efflux of 27 primary amine-containing compounds from the macula and nerve fractions was monitored by cation-exchange HPLC with fluorescence detection, and release by 53.5 mM potassium was determined at 1.45 mM calcium, 0.35 mM magnesium or 0 mM calcium, 10.1 mM magnesium. Taurine was released from the saccular macula in the greatest amount, accounting for 72% of the total evoked release of primary amine-containing compounds. Its release was calcium dependent and its time course prolonged. The contribution by myelinated nerve and associated Schwann cells within the macula to overall release of taurine from the macula in the presence of calcium, as determined from the saccular nerve preparation, was only 2%. Other components specifically released from the macula included ethanolamine, phosphoserine, beta-alanine, and glycine. Glutamate and aspartate were released from both the macula and saccular nerve fractions by potassium in the presence of calcium and in a ratio of 6:1 (glutamate:aspartate) for the macula and 7.5:1 for the nerve. The release of aspartate, but not that of glutamate, was lowered in saline containing 0 mM calcium, 10.1 mM magnesium. The calculated contribution from neural elements to overall release from the macula was 10% for aspartate and 18% for glutamate. These studies demonstrate that both the macula and saccular nerve fractions release the 'excitatory neurotransmitter' candidates aspartate and glutamate. Calcium-dependent, potassium-evoked release of taurine appears to be specific to the hair cell-supporting cell population of the saccular macula, and taurine may, therefore, be involved directly or indirectly in hair cell neurotransmission in labyrinthine organs. This study represents the first detailed biochemical characterization of efflux and release for an in vitro hair cell system of relatively high purity with respect to hair cells.
含有大量毛细胞的虹鳟鱼球囊斑体外制备物，可作为听侧线毛细胞-传入神经突触释放神经递质的潜在来源。与之平行维持的球囊神经体外制备物，用于表明神经对球囊斑整体释放的潜在贡献。通过阳离子交换高效液相色谱结合荧光检测监测27种含伯胺化合物从斑和神经部分的流出，并在1.45 mM钙、0.35 mM镁或0 mM钙、10.1 mM镁的条件下测定53.5 mM钾引起的释放。牛磺酸从球囊斑中释放量最大，占含伯胺化合物总诱发释放量的72%。其释放依赖于钙，且时程延长。根据球囊神经制备物测定，在有钙的情况下，球囊斑内的有髓神经和相关施万细胞对牛磺酸从球囊斑整体释放的贡献仅为2%。从斑中特异性释放的其他成分包括乙醇胺、磷酸丝氨酸、β-丙氨酸和甘氨酸。在有钙的情况下，钾可使谷氨酸和天冬氨酸从斑和球囊神经部分释放，斑中谷氨酸与天冬氨酸的释放比例为6:1，神经中为7.5:1。在含0 mM钙、10.1 mM镁的盐水中，天冬氨酸的释放降低，但谷氨酸的释放未受影响。计算得出神经成分对斑整体释放的贡献，天冬氨酸为10%，谷氨酸为18%。这些研究表明，斑和球囊神经部分均释放“兴奋性神经递质”候选物天冬氨酸和谷氨酸。钙依赖的、钾诱发的牛磺酸释放似乎是球囊斑毛细胞-支持细胞群体特有的，因此牛磺酸可能直接或间接参与迷路器官中的毛细胞神经传递。本研究首次对相对高纯度的体外毛细胞系统的流出和释放进行了详细的生化表征。
