Postnatal development of GABAergic neurons in the gerbil cochlear nucleus: pre-embedding and post-embedding...

The purpose of this investigation was to compare the results obtained when plastic-embedded sections and vibratome-sliced sections were used to localize gamma-aminobutyric acid immunoreactivity (GABA-IR) in the gerbil cochlear nucleus (CN) during postnatal development. GABA-IR was mainly located in the perikarya of the neurons of the gerbil CN. At two days old, GABA-IR was found in plastic sections. No discernible GABA-IR was found in the vibratome slices at three to four days. At eight days, anti-GABA labeled cells were randomly located in the superficial and deep layer of the dorsal cochlear nucleus (DCN) in the vibratome sections, whereas they were mainly accumulated in the vicinity of the granule layer between the junction of the DCN and posteroventral cochlear nucleus (PVCN) in the plastic sections. At 14 days, anti-GABA labeled cells were reduced in number in the superficial third of the DCN in the vibratome slices and reduced in number in the junction between the DCN and PVCN in the plastic sections. At that time, a striking change was the formation of lamellation of the anti-GABA labeled cells mainly located in the middle third (fusiform layer) of the DCN in the plastic sections. A similar pattern of lamellation was found in the vibratome slices at 17-18 days. At three, four, six and eight weeks, the anti-GABA labeled cells were mainly located in the ventral part of the DCN close to the choroidal plexuses and the ventral part of the PVCN in the plastic sections. At six to 15 months old, distinct anti-GABA labeled cells were located in the fusiform layer of the DCN and scattered in the PVCN in the plastic sections. Another striking change at this age was that numerous vacuoles with a mesh-like network were present in the PVCN.