Fine structure of the cell clusters in the cochlear nerve root: stellate, granule, and mitt cells offer insights into the synaptic organization of local circuit neurons.
The small cell shell of the cochlear nucleus contains a complex integrative machinery which can be used to study the roles of interneurons in sensory processing. The cell clusters in the cochlear nerve root of the chinchilla provide the simplest example of this structure. Reported here are the neuronal architecture and synaptic organization of the three principal cell types and the three distinctive neuropil structures that could be characterized with the Nissl and Golgi methods and electron microscopy. Granule cells were characterized by several dendrites with claw-like terminals that received synaptic contacts from multiple excitatory mossy fiber rosettes. Given their relatively large number and their prolific parallel fiber synapses, the granule cells provide a suitable substrate for a tangential spread of excitatory activity, which could build to considerable proportions. The mitt cells had a thickened, single dendrite, its terminal branches arranged in a shape reminiscent of a baseball catcher's mitt. The dendritic mitt enclosed an enormous, convoluted mossy fiber rosette forming many excitatory synapses on just one cell. This could provide for a discrete, comparatively fast input-output relay of signals. Small stellate cells had longer, radiating dendrites that engaged the synaptic nests. These nests were strung in long strands, containing heterogeneous synapses from putative excitatory and inhibitory inputs. Given the prevalence of the synaptic nests, the small stellate cells appear to have the greatest integrative capacity. They provide the main output of the synaptic nests.
Hutson
K A
KA
Department of Psychology, University of Toledo, Ohio 43606, USA.
Morest
D K
DK
D000818:Animals; D001306:Auditory Pathways / Q000648:ultrastructure; D001369:Axons / Q000648:ultrastructure; D002682:Chinchilla / Q000033:anatomy & histology*; D017626:Cochlear Nucleus / Q000166:cytology* / Q000648:ultrastructure; D003712:Dendrites / Q000648:ultrastructure; D007395:Interneurons / Q000648:ultrastructure; D009411:Nerve Endings / Q000648:ultrastructure; D009474:Neurons / Q000648:ultrastructure*; D013569:Synapses / Q000648:ultrastructure*