Developmental and regional patterns of GAP-43 immunoreactivity in a metamorphosing brain.

Growth-associated protein-43 is typically expressed at high levels in the nervous system during development. In adult animals, its expression is lower, but still observable in brain areas showing structural or functional plasticity. We examined patterns of GAP-43 immunoreactivity in the brain of the bullfrog, an animal whose nervous system undergoes considerable reorganization across metamorphic development and retains a strong capacity for plasticity in adulthood.

Plasticity of auditory medullary-midbrain connectivity across metamorphic development in the bullfrog, Rana catesbeiana.

On the basis of patterns of anterograde, retrograde, and bi-directional transport of tracers from both the superior olivary nucleus (SON) and the torus semicircularis (TS), we report anatomical changes in brainstem connectivity across metamorphic development in the bullfrog, Rana catesbeiana. In early and late stages of larval development (Gosner stages 25-37), anterograde or bi-directional tracers injected into the SON produce terminal/fiber label in the contralateral SON and in the ipsilateral TS. Between stages 38-41 (deaf period), only sparse or no terminal/fiber label is visible in these target nuclei.

Developmental changes in cell proliferation in the auditory midbrain of the bullfrog, Rana catesbeiana.

We examined patterns of cell proliferation in the auditory midbrain (torus semicircularis) of the bullfrog, Rana catesbeiana, over larval and early postmetamorphic development, by visualizing incorporation of 5-bromo-2'-deoxyuridine (BrdU) in cycling cells. At all developmental stages, BrdU-labeled cells were concentrated around the optic ventricle. BrdU-labeled cells also appeared within the torus semicircularis itself, in a stage-specific manner.

Cell proliferation in the Rana catesbeiana auditory medulla over metamorphic development.

During metamorphic development, bullfrogs (Rana catesbeiana) undergo substantial morphological, anatomical, and physiological changes as the animals prepare for the transition from a fully-aquatic to a semi-terrestrial existence. Using BrdU incorporation and immunohistochemistry, we quantify changes in cell proliferation in two key auditory brainstem nuclei, the dorsolateral nucleus and the superior olivary nucleus, over the course of larval and early postmetamorphic development. From hatchling through early larval stages, numbers of proliferating cells increase in both nuclei, paralleling the overall increase in total numbers of cells available for labeling.

Metamorphic changes in GABA immunoreactivity in the brainstem of the bullfrog, Rana catesbeiana.

We examined immunoreactivity for gamma-aminobutyric acid (GABA) in auditory and vestibular brainstem nuclei of the bullfrog, Rana catesbeiana, across metamorphosis, a developmental period featuring significant anatomical and functional remodeling of the nervous system. In the early larval period, GABA-immunoreactive cell somata were visible in the vestibular nucleus complex and the torus semicircularis, as well as in the spinal cord, cerebellum and optic tectum. Fiber bundles such as the medial longitudinal fasciculus and the lemnsical pathways also exhibited intense label at these early stages.