Quantal and nonquantal transmission in calyx-bearing fibers of the turtle posterior crista
Quantal and nonquantal transmission in calyx-bearing fibers of the turtle posterior crista
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DOI：
10.1152/jn.00332.2007
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发表时间：
2007-09-01
影响因子：
2.5
通讯作者：
Goldberg, Jay M.
中科院分区：
文献类型：
--
作者：
Holt, Joseph C.;Chatlani, Shilpa;Goldberg, Jay M.
细胞内记录由神经上皮附近的后壶腹神经中的神经纤维制成。花萼轴承传入确定其独特的传出介导的反应。这些纤维接受来自I型和II型毛细胞的输入。II型输入是由在花萼末端的外表面上和在二形纤维的终扣上的突触进行的。量子活性，由简短的mEPSPs，降低外部浓度的Ca 2+和AMPA受体拮抗剂CNQX阻断。泊松统计控制mEPSP的时间，在没有机械刺激的情况下，mEPSP以高速率（250- 2，500/s）发生。导管压痕产生的激励可以将mEPSP速率增加到近5，000/s。随着速率的增加，mEPSP可以从单相去极化变为双相去极化-超极化序列，其两个组分都被CNQX阻断。电压门控电流的阻断剂影响mEPSP的大小，TTX可降低mEPSP的大小，而linopirdine可增加mEPSP的大小。穿刺后mEPSP大小减小数倍。尽管在穿刺过程中发生的去极化可能会触发尺寸减小，但即使在超极化膜电位下也会持续减小。散粒噪声计算和量子活动被取消后的电压调制的存在表明非量子传输。超微结构研究表明，来自I型毛细胞的内面输入数量超过来自II型毛细胞的外面输入数量，比例几乎为6：1。
Intracellular recordings were made from nerve fibers in the posterior ampullary nerve near the neuroepithelium. Calyx-bearing afferents were identified by their distinctive efferent-mediated responses. Such fibers receive inputs from both type I and type II hair cells. Type II inputs are made by synapses on the outer face of the calyx ending and on the boutons of dimorphic fibers. Quantal activity, consisting of brief mEPSPs, is reduced by lowering the external concentration of Ca2+ and blocked by the AMPA-receptor antagonist CNQX. Poisson statistics govern the timing of mEPSPs, which occur at high rates (250-2,500/s) in the absence of mechanical stimulation. Excitation produced by canal-duct indentation can increase mEPSP rates to nearly 5,000/s. As the rate increases, mEPSPs can change from a monophasic depolarization to a biphasic depolarizing-hyperpolarizing sequence, both of whose components are blocked by CNQX. Blockers of voltage-gated currents affect mEPSP size, which is decreased by TTX and is increased by linopirdine. mEPSP size decreases severalfold after impalement. The size decrease, although it may be triggered by the depolarization occurring during impalement, persists even at hyperpolarized membrane potentials. Nonquantal transmission is indicated by shot-noise calculations and by the presence of voltage modulations after quantal activity is abolished pharmacologically. An ultrastructural study shows that inner-face inputs from type I hair cells outnumber outer-face inputs from type II hair cells by an almost 6:1 ratio.