[Lamellar structure of the dorsal cochlear nucleus in rats].

The lamellar ultrastructure of the dorsal cochlear nucleus (DCN) was studied in frontal ultrathin wide sections of the nucleus which were placed on lead aprons and included all the nucleus layers. The electron-microscopic description of the different cell types and distribution of the axonal terminals are presented. Large branchy axonal terminals (6-8micron) with small spherical synaptic vesicles 40-50 nm in diameter, small terminals (1-3 micron) with spherical synaptic vesicles (45-60 nm) and thin unmyelinated axons prevail in the surface and middle layers of the neuropile as compared to the deep layer. The number of the myelinated axons and large oval terminals 4-6 micron in diameter with central distribution of mitochondria and neurofilaments as well as with spherical synaptic vesicles 50-60 nm in diameter increased from the middle layer to the deep one. The number of granular cells was larger in the surface and middle layers than in the deep one. The functional significance of each terminal type is discussed.