Short-term synaptic depression and recovery at the mature mammalian endbulb of Held synapse in mice.
Short-term synaptic depression and recovery at the mature mammalian endbulb of Held synapse in mice.
复制标题
小鼠 Held 突触成熟哺乳动物端球的短期突触抑制和恢复。
DOI：
10.1152/jn.90715.2008
复制
发表时间：
2008
影响因子：
2.5
通讯作者：
Manis,PaulB
中科院分区：
文献类型：
--
作者：
Wang,Yong;Manis,PaulB
听觉神经纤维（ANF）和耳蜗核丛状神经元之间的Held突触的内球传递嵌入在传入声信号中的精细时间信息。突触抑制和恢复的动力学是调节球内突触突触传递的关键。我们研究了成熟（P22-38）CBA小鼠的短期突触抑制和恢复，刺激率与体内记录的声音驱动活动相当。成熟小鼠中的突触抑制比未成熟动物中报道的严重程度低（在100 Hz下为40%），并且这种抑制主要是由于可释放囊泡的耗尽。抑郁症的恢复取决于突触前末梢细胞内Ca 2+的活性和积累率。在2 mM外部[Ca 2 +]中以100 Hz的常规刺激序列，从耗尽的恢复是缓慢的（τ慢，τ 2 s）。相反，当刺激速率或外部[Ca 2 +]增加时，观察到快速（τ快，1025 ms）的Ca 2+依赖性恢复，随后是较慢的恢复（τ慢，102 s）。在正常的[Ca 2 +]中，从100 Hz的泊松样列车中恢复是迅速的，这表明泊松样列车比常规列车产生更高的内部[Ca 2 +]。此外，在钙咪达唑盐（一种Ca 2 +/钙调蛋白抑制剂）的存在下，快速恢复减慢约两倍。我们的研究结果表明，高自发放电率的听神经纤维的球内突触通常在抑郁状态下工作。在高活动率期间加速的突触恢复可能确保在球内突触处可以实现可靠的突触传递。
The endbulb of Held synapses between the auditory nerve fibers (ANF) and cochlear nucleus bushy neurons convey fine temporal information embedded in the incoming acoustic signal. The dynamics of synaptic depression and recovery is a key in regulating synaptic transmission at the endbulb synapse. We studied short-term synaptic depression and recovery in mature (P22-38) CBA mice with stimulation rates that were comparable to sound-driven activities recorded in vivo. Synaptic depression in mature mice is less severe (∼40% at 100 Hz) than reported for immature animals and the depression is predominately due to depletion of releasable vesicles. Recovery from depression depends on the rate of activity and accumulation of intracellular Ca2+at the presynaptic terminal. With a regular stimulus train at 100 Hz in 2 mM external [Ca2+], the recovery from depletion was slow (τslow, ∼2 s). In contrast, a fast (τfast, ∼25 ms), Ca2+-dependent recovery followed by a slower recovery (τslow, ∼2 s) was seen when stimulus rates or external [Ca2+] increased. In normal [Ca2+], recovery from a 100-Hz Poisson-like train is rapid, suggesting that Poisson-like trains produce a higher internal [Ca2+] than regular trains. Moreover, the fast recovery was slowed by approximately twofold in the presence of calmidazolium, a Ca2+/calmodulin inhibitor. Our results suggest that endbulb synapses from high spontaneous firing rate auditory nerve fibers normally operate in a depressed state. The accelerated synaptic recovery during high rates of activity is likely to ensure that reliable synaptic transmission can be achieved at the endbulb synapse.