The Journal of Neuroscience, September 15, 1999, 19(18):7757-7769
Differential Expression of Brain-Derived Neurotrophic Factor,
Neurotrophin-3, and Neurotrophin-4/5 in the Adult Rat Spinal Cord:
Regulation by the Glutamate Receptor Agonist Kainic Acid
Isobel A.
Scarisbrick1, 2,
Paul J.
Isackson1, and
Anthony J.
Windebank2
1 Department of Biochemistry and Molecular Biology,
Mayo Clinic Jacksonville, Jacksonville, Florida 32224, and
2 Molecular Neuroscience Research, Mayo Clinic Rochester,
Rochester, Minnesota 55905
Previous in vitro studies indicate that select
members of the neurotrophin gene family, namely brain-derived
neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4/5
(NT-4/5), contribute to survival and differentiation of spinal cord
motoneurons. To investigate the potential roles of these factors in the
adult spinal cord, we examined their cellular localization and
regulation after systemic exposure to an excitotoxic stimulus, kainic
acid (KA).
Of the neurotrophins examined, NT-4/5 mRNA was most robustly expressed
in the lumbosacral spinal cord of the normal adult rat, including
expression by neurons throughout the gray matter, and in a
subpopulation of white and gray matter glia. Both BDNF and NT-3 mRNAs
were also densely expressed by
motoneurons of lamina IX, but were
detected at lower levels elsewhere in the gray matter. NT-3 mRNA was
additionally expressed by spinal cord glia, but was less widespread
compared to NT-4/5. In response to systemic administration of KA,
NT-4/5 and BDNF mRNAs were dramatically upregulated in a spatially and
temporally restricted fashion, whereas levels of NT-3 mRNA were
unchanged. These results provide strong in vivo evidence
to support the idea that BDNF, NT-3, and in particular, NT-4/5, play a
role in the normal function of the adult spinal cord. Furthermore, our
results indicate that the actions of BDNF and NT-4/5 participate in the
response of the cord to excitotoxic stimuli, and that those of NT-4/5
and NT-3 include both neurons and glia.
Key words:
neurotrophin; motoneuron; glia; oligodendrocyte; kainic
acid; spinal cord injury
Copyright © 1999 Society for Neuroscience 0270-6474/99/19187757-13$05.00/0