Original Paper

Developmental and Regional Patterns of GAP-43 Immunoreactivity in a Metamorphosing Brain
Andrea Megela Simmons^{a, b}, Leslie H. Tanyu^a, Seth S. Horowitz^{a, b}, Judith A. Chapman^a, Rebecca A. Brown^a

Departments of
^aPsychology and
^bNeuroscience, Brown University, Providence, R.I., USA

Address of Corresponding Author

Brain Behav Evol 2008;71:247-262 (DOI: 10.1159/000127045)

  Key Words

• Growth-associated protein 43
• Plasticity
• Metamorphosis
• Bullfrog
• Midbrain
• Forebrain
• Cranial nerves

  Abstract

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. Immunolabeling was mostly diffuse in hatchling tadpoles, but became progressively more discrete as larval development proceeded. In many brain areas, intensity of immunolabel peaked at metamorphic climax, the time of final transition from aquatic to semi-terrestrial life. Changes in intensity of GAP-43 expression in the medial vestibular nucleus, superior olivary nucleus, and torus semicircularis appeared correlated with stage-dependent functional changes in processing auditory stimuli. Immunolabeling in the Purkinje cell layer of the cerebellum and in the cerebellar nucleus was detectable at most developmental time points. Heavy immunolabel was present from early larval stages through the end of climax in the thalamus (ventromedial, anterior, posterior, central nuclei). Immunolabel in the tadpole telencephalon was observed around the lateral ventricles, and in the medial septum and ventral striatum. In postmetamorphic animals, immunoreactivity was confined mainly to the ventricular zones and immediately adjacent cell layers. GAP-43 expression was present in olfactory, auditory and optic cranial nerves throughout larval and postmetamorphic life. The continued expression of GAP-43 in brain nuclei and in cranial nerves throughout development and into adulthood reflects the high regenerative potential of the bullfrog's central nervous system.

Copyright © 2008 S. Karger AG, Basel

  Author Contacts

A.M. Simmons
Department of Psychology, Box 1853, Brown University
Providence, RI 02912 (USA)
Tel. +1 401 863 2283, Fax +1 401 863 1300
E-Mail Andrea_Simmons@brown.edu

  Article Information

Received: October 19, 2007
Returned for revision: December 21, 2007
Accepted after revision: January 11, 2008
Published online: April 21, 2008
Number of Print Pages : 16
Number of Figures : 6, Number of Tables : 1, Number of References : 57