Synaptic reoponses in Olivocochlear neurons of the rat.

点击翻译按钮获取中文摘要

Olivocochlear (OC) neurons are efferent auditory neurons that project to the cochlea, and regulate the peripheral signal processing. We have previously reported on their intrinsic membrane properties in slice preparation of the rat using the whole-cell patch recording configuration (J. Neurophysiology 77,2788,1997). In this study, we further investigated the synaptic inputs to these neurons. We recorded EPSCs from two groups of OC(LOC and MOC)neurons and the principal neurons of the lateral superior olive(LSO neurons)which is the afferent auditory neurons, as a reference. Both non-NMDA and NMDA receptor mediated postsynaptic currents were present in the three groups of neurons. Individual neurons of these three groups showed glycinergic and GABAergic synaptic responses. Besides these amino acid responses, LOC neurons also showed dtubocularine-sensitive nicotinic receptor mediated responses when acetylcholine was puff applied. Previous anatomical studies have reported the presence of recurrent collateral axons in LOC neurons that innervate LSO including LOC neurons themselves. Since LOC neurons are known to be cholinergic, these observations suggest a synchronous excitation mechanism among neighbored LOC neurons. LOC neurons are supposed to be arranged tonotopically in LSO, and to project to the corresponding characteristic frequency region of the cochlea. Therefore, the synchronous excitation of a group of LOC neurons might effectively enhance the auditory signals in a particular frequency region.