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Updated: Sep 23, 2026
Long-range Channelrhodopsin-assisted Circuit Mapping of Inferior Colliculus Neurons with Blue and Red-shifted Channelrhodopsins
Published on: February 7, 2020
Macroglia distribution in the developing and adult inferior colliculus
Aziz Hafidi1, Dimetrios Galifianakis
1Laboratoire de Biologie Cellulaire et Moleculaire de l'Audition, INSERM EMI 99-27, Université Bordeaux-2, Hôpital Pellegrin, PQR3, 33076 Bordeaux, France. azhafidi@univ-bpclermont.fr
Abstract:
Macroglia distribution in the developing and adult gerbil inferior colliculus (IC) was investigated using two oligodendrocytic [myelin-associated-glycoprotein (MAG) and oligodendrocyte-specific molecule (Rip)] and two astrocytic [glial fibrillary acidic protein (GFAP) and S100] markers and immunohistochemistry. There was a spatio-temporal pattern of myelin marker expression starting in the ventral area of the IC and continuing to the dorsal part of the nucleus. Myelination, as revealed by MAG and Rip markers, starts in the IC during the second postnatal week. The intensity of myelination increased between stages P15 and P21 and extended to the whole IC. The appearance of myelin proteins in the IC may suggest a possible axonal outgrowth inhibition by oligodendrocytes in this structure. A differential pattern of staining was obtained with S100 and GFAP antibodies. Astrocytes identified as S100 immunoreactive cells were observed in the IC by birth and the staining was localized to their cell body and processes. S100 positive cells were homogeneously distributed within the IC nucleus. S100 pattern of staining remained the same in stages P7, P15 and P21. In adult IC, S100 positive cell processes were in contact with neuronal cell bodies, other S100 positive cells and blood vessels. Quantitative analysis showed an increase in the density of positive cells during the first postnatal week and a decrease then after through to adulthood. Unlike S100, GFAP immunoreactivity showed a different pattern of staining. At birth GFAP positive astrocytes were observed along the collicular brain midline and around the IC nucleus delimiting its boundaries. The GFAP pattern of labelling remained the same during development and in the adult. This data suggests the presence of two astrocytes subtypes with different locations in the IC nucleus. The GFAP positive astrocytes were located along the edge of the nucleus, while the S100 positive ones displayed a homogeneous distribution across the nucleus.
Insights
This study maps macroglia in the gerbil inferior colliculus (IC), revealing distinct myelination patterns and two astrocyte subtypes. Oligodendrocytes myelinate the IC postnatally, while S100 and GFAP astrocytes show unique distributions.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- The inferior colliculus (IC) is a crucial auditory processing center.
- Understanding macroglia development is key to auditory pathway maturation.
- Oligodendrocytes and astrocytes play vital roles in neural development and function.
Purpose of the Study:
- To investigate the spatio-temporal distribution of oligodendrocytes and astrocytes in the developing and adult gerbil IC.
- To characterize the expression patterns of myelin-associated glycoprotein (MAG), oligodendrocyte-specific molecule (Rip), glial fibrillary acidic protein (GFAP), and S100 markers.
- To identify potential roles of macroglia in IC development and axonal regulation.
Main Methods:
- Immunohistochemistry was employed using specific markers for oligodendrocytes (MAG, Rip) and astrocytes (GFAP, S100).
- Gerbil brains at various postnatal stages (birth, P7, P15, P21) and adulthood were analyzed.
- Quantitative analysis was performed to assess cell density and distribution.
Main Results:
- Myelination, marked by MAG and Rip, begins in the second postnatal week, progressing from ventral to dorsal IC.
- Oligodendrocyte myelination intensity increases between P15 and P21, covering the entire IC.
- Two distinct astrocyte populations were identified: S100-positive cells homogeneously distributed throughout the IC, and GFAP-positive cells located at the IC's boundaries.
Conclusions:
- The gerbil IC undergoes significant myelination during early postnatal development.
- The presence of two astrocyte subtypes with distinct localizations suggests specialized functions within the IC.
- Macroglia, particularly oligodendrocytes, may influence axonal development and circuit formation in the auditory midbrain.
