Atlas of the Subcortical Central Auditory System of the Cat
This atlas created by Joe Adams includes three sets of
The Nissl stain shows nucleic acids (DNA and
RNA), which means that cell nuclei and ribosomes (both free and those
attached to rough endoplasmic reticulum) are visualized. Staining of
RNA is useful for identification of gross structures such as whole nuclei,
as shown in the low magnification images, and of distinctive features of
individual cells, as shown in the high magnification images. While the
Nissl technique shows all cells, immunostaining only reveals those
cells containing a specific protein and is therefore useful for identifying
cytochemically distinct types of cells.
Low-magnification Nissl-stained sections
There are low magnification views of 24 Nissl-stained sections
spanning the entire subcortical auditory pathway from the dorsal cochlear nucleus (DCN) to the
medial geniculate body (MGB) of the thalamus. The successive images are spaced
apart and are numbered beginning caudally with the DCN and progressing rostrally
down the columns of images. Each figure contains 6 images.
The numbers of individual figures in these low magnification
views indicate the sections from which the high-magnification micrographs were
taken. For example, all the high-magnification images shown in the anterior
periolivary region (APO) figure were taken from the tissue shown in Section Number 9 of the low-
magnification series (the area labeled APO in the
NLL series), as
indicated by all images in this figure being numbered 9A, 9B, etc...
High-magnification Nissl-stained sections
High magnification images (500X) were
obtained with a 40X objective in combination with a 12.5X photo ocular.
For cells in auditory nuclei caudal to the inferior
colliculus, this magnification is quite informative for showing distinctive
features of particular cell classes, e.g., their size, shape, and pattern of Nissl substance.
Superior olivary complex
Nuclei of the lateral lemniscus
Other distinctive features of particular cell classes are
revealed by immunostaining. Three figures show different examples.
Comparison of Nissl stain
vs. immunostaining for calbindin in the DCN. For example, in Plate 1D,
cells stand out when stained for calbindin. Calbindin
(CaBP) is a calcium-binding protein whose precise functional role in
cartwheel cells is unknown. It is shown here as an illustration of the
fact that cytochemical traits can be used to identify particular cell
classes. Note how conspicuous the calbindin
immunostained cells are when compared to the adjacent Nissl stained section of
the same region (Plate 1A). The other 4 Nissl-stained plates (1B-C, 1-EF)
show high-magnification views of cells in Plate 1A.
Cochlear-nucleus cells immunostained for
GAD, the enzyme directly responsible for production of the inhibitory
neurotransmitter GABA. Each of the 6 plates is described below.
DCN is a layered structure. The outermost, ependymal
layer (which contains no neurons) is unstained, while the second, molecular
layer layer stains darkly due to the presence of GABAergic processes that
terminate upon the dendrites of cartwheel cells and the apical dendrites
of pyramidal cells. The somata of pyramidal cells form the third, pyramidal
layer, which is largely unstained. The less darkly stained deep DCN contains large cells and
vertical cells, whose processes receive many GABAergic terminals, but
fewer than those in the molecular layer.
nerve root region (where the AN axons enter the CN),
there are considerable differences in the
density of GABAergic processes, but there are no distinctive layers of cells or stained processes, as in the DCN.
The AVCN is more uniformly stained than the nerve root region.
The numerous small clear dots surrounded by dense staining are spherical
bushy cells, which have a dense GABAergic innervation on their somata (which appears as
a dense, dark band around the unstained, clear cells). This innervation appears to be almost as dense as the innervation
that these cells receive from auditory-nerve fibers. The origins and functions of
this GABAergic innervation are unknown.
High-magnification view of several cells in the nerve
root region demonstrates the differences in GABAergic innervation
in this small field of view. At the top of the micrograph are two neurons that
are covered with coarse, dense GABAergic terminals. In contrast, in the lower
half of the field, several cells receive fine, sparse innervation.
The latter are probably Type 1 stellate cells. The former are either
stellate cells or globular bushy cells.
Similar comparison in the
octopus cell region of the PVCN.
In the left half of the field are octopus cells, which have barely any GABAergic
input. In the right half are a few Type 2 stellate cells, which are densely
PVCN cells receive a relatively dense covering of fine
GABAergic terminals. The size, density and placement of GABAergic inputs contribute to
the physiological properties of the target neurons. It is therefore expected that physiologically-distinct classes of cells will
have characteristic staining patterns in their inputs, as shown in these
Cytochemical traits of SOC
neurons distinguished by immunostaining for AchE, GAD or calbindin. Each of the 6 plates is described below.
acetylcholinesterase (AChE, the enzyme
that degrades acetylcholine and is a useful marker for cholinergic neurons) in
the hilus (dorsal indentation) of the LSO. The dark
staining shows the locations of the lateral olivocochlear (LOC) neurons
which project to the inner hair cell region in the cochlea.
staining in the anterior periolivary region (APO). The dark
staining shows the medial olivocochlear (MOC) neurons which project to
outer hair cells in the cochlea.
The hilus of the LSO has a relatively dense GABAergic
innervation as shown by GAD staining.
Sparse, large multipolar cells located along the
margins of the MSO also have a dense GABAergic innervation.
Dense GABAergic innervation surrounding MNTB principal
neurons (much like that seen on spherical bushy cells in AVCN) and the VNTB neuropil.
Calbindin immunostaining of MNTB cells (lower left of
the image) and the dense terminals of the projections of these cells to both MSO (center of the field) and LSO (upper
cells. The MNTB cells are
glycinergic and provide contralateral inhibitory inputs to MSO and LSO. Humans lack a
pronounced MNTB and LSO, but have a large MSO. Consequently, the human MSO
little inhibitory input from the contralateral ear, as is present in