Grant Lisa, Yi Eunyoung, Goutman Juan D, Glowatzki Elisabeth
Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins School of Medicine, USA.
J Vis Exp. 2011 Feb 10(48):2442. doi: 10.3791/2442.
The afferent synapse between the inner hair cell (IHC) and the auditory nerve fiber provides an electrophysiologically accessible site for recording the postsynaptic activity of a single ribbon synapse. Ribbon synapses of sensory cells release neurotransmitter continuously, the rate of which is modulated in response to graded changes in IHC membrane potential. Ribbon synapses have been shown to operate by multivesicular release, where multiple vesicles can be released simultaneously to evoke excitatory postsynaptic currents (EPSCs) of varying amplitudes. Neither the role of the presynaptic ribbon, nor the mechanism underlying multivesicular release is currently well understood. The IHC is innervated by 10-20 auditory nerve fibers, and every fiber contacts the IHC with a unmyelinated single ending to form a single ribbon synapse. The small size of the afferent boutons contacting IHCs (approximately 1 μm in diameter) enables recordings with exceptional temporal resolution to be made. Furthermore, the technique can be adapted to record from both pre- and postsynaptic cells simultaneously, allowing the transfer function at the synapse to be studied directly. This method therefore provides a means by which fundamental aspects of neurotransmission can be studied, from multivesicular release to the elusive function of the ribbon in sensory cells.
内毛细胞（IHC）与听神经纤维之间的传入突触提供了一个电生理可及的位点，用于记录单个带状突触的突触后活动。感觉细胞的带状突触持续释放神经递质，其释放速率会根据内毛细胞膜电位的分级变化进行调节。已证明带状突触通过多泡释放来运作，即多个囊泡可同时释放，以引发不同幅度的兴奋性突触后电流（EPSC）。目前，人们对突触前带状物的作用以及多泡释放的潜在机制都还了解甚少。内毛细胞由10 - 20根听神经纤维支配，每根纤维都以无髓鞘的单个末梢与内毛细胞接触，形成单个带状突触。与内毛细胞接触的传入终扣体积小（直径约1μm），这使得能够进行具有出色时间分辨率的记录。此外，该技术可适用于同时记录突触前和突触后细胞，从而直接研究突触处的传递函数。因此，这种方法提供了一种手段，通过它可以研究神经传递的基本方面，从多泡释放到感觉细胞中带状物难以捉摸的功能。
