Ultrastructure of synaptic input to medial olivocochlear neurons

被引:16
作者
Benson, Thane E.
Brown, M. Christian
机构
[1] Massachusetts Eye & Ear Infirm, Eaton Peabody Lab, Boston, MA 02114 USA
[2] Harvard Univ, Sch Med, Dept Otol & Laryngol, Boston, MA 02114 USA
[3] Harvard Mit Div Hlth Sci & Technol, Cambridge, MA 02139 USA
关键词
superior olivary complex; efferent; outer hair cell; cochlear nucleus; synaptic vesicle;
D O I
10.1002/cne.21118
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Medial olivocochlear (MOC) neurons project from the brain to the cochlea to form the efferent limb of the MOC reflex. To study synaptic inputs to MOC neurons, we retrogradely labeled these neurons using horseradish peroxidase injections into the cochlea. Labeled neurons were identified in the ventral nucleus of the trapezoid body and documented with the light microscope before being studied with serial-section electron microscopy. MOC somata and dendrites were innervated by three different types of synapses, distinguished as either having: 1) large, round synaptic vesicles and forming asymmetric contacts; 2) small, round vesicles plus a few dense core vesicles and forming asymmetric contacts; or 3) pleomorphic vesicles and forming symmetric contacts. The first two types were the most frequent on somata. Acetylcholinesterase-stained material confirmed that the type containing large, round vesicles is most common on dendrites. We kept track of the synaptic terminals in serial sections and compiled them into three-dimensional swellings. Swellings with large, round vesicles formed up to seven synapses per swelling, were largest in size, and sometimes formed complex arrangements engulfing spines of MOC neurons. Swellings with small, round vesicles formed up to four synapses per swelling. The morphology of this type of synapse, and the moderate sizes of the swellings forming it, suggests that it originates from posteroventral cochlear nucleus stellate/multipolar neurons. This input may thus provide the sound-evoked input to MOC neurons that causes their reflexive response to sound.
引用
收藏
页码:244 / 257
页数:14
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