Cytology, synaptology and immunocytochemistry of commissural neurons and their putative axonal terminals in the dorsal cochlear nucleus of the rat

Authors
Citation
L. Alibardi, Cytology, synaptology and immunocytochemistry of commissural neurons and their putative axonal terminals in the dorsal cochlear nucleus of the rat, ANN ANATOMY, 182(3), 2000, pp. 207-220
Citations number
48
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Experimental Biology
Journal title
ANNALS OF ANATOMY-ANATOMISCHER ANZEIGER
ISSN journal
0940-9602 → ACNP
Volume
182
Issue
3
Year of publication
2000
Pages
207 - 220
Database
ISI
SICI code
0940-9602(200005)182:3<207:CSAIOC>2.0.ZU;2-2
Abstract
The first binaural integration within the auditory system responsible for s ound localization depends upon commissural neurons that connect the two sym metrical cochlear nuclei. These cells in the deep polymorphic layer of the rat dorsal cochlear nucleus were identified with the electron microscope af ter injection of the retrograde tracer, Wheat Germ Agglutinin conjugated to Horseradish Peroxydase, into the contralateral cochlear nucleus. Commissur al neurons are multipolar or bipolar with an oval to fusiform shape. Few co mmissural neurons, most inhibitory but also excitatory, connect most of the divisions of the rat cochlear nuclei. The most common type is a glycinergi c, sometimes GABAergic, moderately large cell. Its ergastoplasm is organize d into peripheral stacks of cisternae, and few axe-somatic synaptic boutons are present. Another type of commissural neuron is a medium-sized, spindle -shaped cell, glycine and GABA-negative, with sparse ergastoplasm and synap tic coverage. A giant, rare type of commissural neuron is glycine-positive and GABA-negative, with short peripheral stacks of ergastoplasmic cisternae . It is covered with synaptic boutons, many of which contain round synaptic vesicles. Another rare type of commissural neuron is a moderately large ce ll, oval to fusiform in shape, immunonegative for both glycine and GABA, an d contacted by many axe-somatic boutons. It contains large dense mitochondr ia and numerous dense core vesicles of peptidergic type. Some labelled bout ons, mostly inhibitory and probably derived from commissural neurons, conta ct pyramidal, cartwheel, giant and tubercule-ventral neurons. The prevalent inhibition of electrical activity in a cochlear nucleus observed after sti mulation of the contralateral cochlear nucleus may be due to commissural in hibitory terminals which contact excitatory neurons such as pyramidal and g iant cells. Other inhibitory commissural terminals which contact inhibitory neurons such as cartwheel and tubercule-ventral neurons, may explain the s timulation of electrical activity in the DCN after contralateral stimulatio n.