Prigioni I, Valli P, Guth P S
Boll Soc Ital Biol Sper. 1984 May 30;60(5):993-8.
Following the suggestions in the literature that glutamate or aspartate may be the transmitter at the primary afferent synapses of acoustico-lateralis organs, we have employed the "selective" excitatory amino acid antagonist. D-alpha amino adipate (DAA) as a tool with which to shed further light on this problem in the labyrinthine organs of the frog. DAA produces a dose-responsive, reversible depression of spontaneous activity in the afferent nerves of the posterior semicircular canal, saccule and basilar papilla. These structures are examples of ampullar, otolithic and auditory organs, respectively. The drug effect seems qualitatively the same throughout the labyrinth. The most interesting finding was that of a presynaptic (hair cell) effect of DAA on the semicircular canal. The means of recording did not permit detection of a presynaptic effect in the other organs examined. All the observed effects of DAA could be explained by a presynaptic action to inhibit transmitter release. Therefore, the ability of DAA to reduce transmission at primary afferent synapses of the frog labyrinth must not necessarily be interpreted to imply that the transmitter is an excitatory amino acid. A presynaptic action to reduce the release of a transmitter (of unknown structure) could explain all our results.
根据文献中关于谷氨酸或天冬氨酸可能是听侧线器官初级传入突触处神经递质的建议，我们使用了“选择性”兴奋性氨基酸拮抗剂D-α-氨基己二酸（DAA），作为进一步阐明青蛙迷路器官中这一问题的工具。DAA对后半规管、球囊和基底乳头的传入神经的自发活动产生剂量依赖性、可逆性抑制。这些结构分别是壶腹、耳石和听觉器官的实例。在整个迷路中，药物作用在性质上似乎是相同的。最有趣的发现是DAA对半规管有突触前（毛细胞）效应。记录方法无法检测到在所检查的其他器官中的突触前效应。DAA所有观察到的效应都可以通过抑制递质释放的突触前作用来解释。因此，DAA降低青蛙迷路初级传入突触处传递的能力不一定意味着递质是兴奋性氨基酸。减少一种（结构未知的）递质释放的突触前作用可以解释我们所有的结果。
