Mechanisms of efferent-mediated responses in the turtle posterior crista
Mechanisms of efferent-mediated responses in the turtle posterior crista
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DOI：
10.1523/jneurosci.3539-06.2006
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发表时间：
2006-12-20
影响因子：
5.3
通讯作者：
Goldberg, Jay M.
中科院分区：
文献类型：
--
作者：
Holt, Joseph C.;Lysakowski, Anna;Goldberg, Jay M.
为了研究传出作用的细胞机制，我们对靠近龟后嵴的前庭神经传入神经进行了记录，并对传出纤维进行了电刺激。传出介导的反应来自含花萼（CD、花萼和二形）传入神经和钮扣(B)传入神经，它们的神经上皮位置区分为环面附近的BT单元和中间位置的BM单元。CD单位的尖峰放电受到传出刺激的强烈激发，而BT和BM单位受到抑制，BM单位也表现出抑制后兴奋。阻断尖峰后记录细胞内突触活动。BT/ BM单元对单一传出冲击的响应包括短暂的去极化，随后是长时间的超极化。这两种成分反映了毛细胞量释放率的变化，并被α 9/ α 10烟碱受体的药理学拮抗剂消除。阻断依赖钙的SK钾通道可将双相反应转化为延长的去极化。结果可以解释，在其他毛细胞系统中，通过α 9/ α 10和SK通道的顺序激活。在BM单位中，抑制后的兴奋是基于毛细胞量子的增加速率，并依赖于先前的抑制。此外，还有传出介导的BT/ BM和CD纤维的直接去极化。在CD单元中，它是唯一的传出响应。烟碱拮抗剂对毛细胞的传出作用以及CD和BT/ BM单位的直接去极化有不同的影响。超微结构研究除了证实了II型毛细胞和花萼末端的传出神经支配外，还表明海龟的传出神经通常接触终止于II型毛细胞的传入钮扣。
To study the cellular mechanisms of efferent actions, we recorded from vestibular- nerve afferents close to the turtle posterior crista while efferent fibers were electrically stimulated. Efferent- mediated responses were obtained from calyx- bearing ( CD, calyx and dimorphic) afferents and from bouton ( B) afferents distinguished by their neuroepithelial locations into BT units near the torus and BM units at intermediate sites. The spike discharge of CD units is strongly excited by efferent stimulation, whereas BT and BM units are inhibited, with BM units also showing a postinhibitory excitation. Synaptic activity was recorded intracellularly after spikes were blocked. Responses of BT/ BM units to single efferent shocks consist of a brief depolarization followed by a prolonged hyperpolarization. Both components reflect variations in hair- cell quantal release rates and are eliminated by pharmacological antagonists of alpha 9/alpha 10 nicotinic receptors. Blocking calcium- dependent SK potassium channels converts the biphasic response into a prolonged depolarization. Results can be explained, as in other hair- cell systems, by the sequential activation of alpha 9/alpha 10 and SK channels. In BM units, the postinhibitory excitation is based on an increased rate of hair- cell quanta and depends on the preceding inhibition. There is, in addition, an efferentmediated, direct depolarization of BT/ BM and CD fibers. In CD units, it is the exclusive efferent response. Nicotinic antagonists have different effects on hair- cell efferent actions and on the direct depolarization of CD and BT/ BM units. Ultrastructural studies, besides confirming the efferent innervation of type II hair cells and calyx endings, show that turtle efferents commonly contact afferent boutons terminating on type II hair cells.