Beart P M
Brain Res. 1976 Jun 25;110(1):99-114. doi: 10.1016/0006-8993(76)90211-0.
The possibility was investigated that L-glutamic acid is the excitatory transmitter released from the optic nerve terminals of the pigeon optic tectum. (1) Superficial layers of the tectum contained high levels of endogenous glutamate and accumulated L-[3H]glutamate by a high affinity uptake process. (2) Subcellular and autoradiographic studies indicated that 10-30% of the exogenously accumulated L-[3H]glutamate was localized within synaptosomes, and that 11-15% of the synaptosomes had been labelled. (3) The glutamate-accumulating synaptosomes sedimented to the same isopycnic density as pinched-off optic nerve terminals. (4) GABA-and noradrenaline-accumulating synaptosomes were also associated with this subcellular population. (5) Retinal ablation did not change endogenous glutamate concentrations or the high affinity uptake of glutamate. The results are discussed in relation to a possible role for L-glutamate as the 'optic nerve transmitter' and in the context of previous evidence implicating glutamate as an excitatory transmitter.
对L-谷氨酸是否为鸽子视顶盖视神经末梢释放的兴奋性递质这一可能性进行了研究。（1）顶盖的表层含有高水平的内源性谷氨酸，并通过高亲和力摄取过程积累L-[3H]谷氨酸。（2）亚细胞和放射自显影研究表明，外源积累的L-[3H]谷氨酸中有10 - 30%定位于突触小体，且11 - 15%的突触小体被标记。（3）积累谷氨酸的突触小体沉降到与夹断的视神经末梢相同的等密度。（4）积累GABA和去甲肾上腺素的突触小体也与这一亚细胞群体相关。（5）视网膜切除并未改变内源性谷氨酸浓度或谷氨酸的高亲和力摄取。结合L-谷氨酸作为“视神经递质”的可能作用以及之前暗示谷氨酸为兴奋性递质的证据对结果进行了讨论。
