title: GAP-43 mRNA in Rat Spinal Cord and Dorsal Root Ganglia Neurons: Developmental Changes and Re-expression Following Peripheral Nerve Injury.
abstract: The expression of growth-associated protein GAP-43 mRNA in spinal cord and dorsal root ganglion (DRG) neurons has been studied using an enzyme linked in situ hybridization technique in neonatal and adult rats. High levels of GAP-43 mRNA are present at birth in the majority of spinal cord neurons and in all dorsal root ganglion cells. This persists until postnatal day 7 and then declines progressively to near adult levels (with low levels of mRNA in spinal cord motor neurons and 2000 - 3000 DRG cells expressing high levels) at postnatal day 21. A re-expression of GAP-43 mRNA in adult rats is apparent, both in sciatic motor neurons and the majority of L4 and L5 dorsal root ganglion cells, 1 day after sciatic nerve section. High levels of the GAP-43 mRNA in the axotomized spinal motor neurons persist for at least 2 weeks but decline 5 weeks after sciatic nerve section, with the mRNA virtually undetectable after 10 weeks. The initial changes after sciatic nerve crush are similar, but by 5 weeks GAP-43 mRNA in the sciatic motor neurons has declined to control levels. In DRG cells, after both sciatic nerve section or crush, GAP-43 mRNA re-expression persists much longer than in motor neurons. There was no re-expression of GAP-43 mRNA in the dorsal horn of the spinal cord after peripheral nerve lesions. Our study demonstrates a similar developmental regulation in spinal cord and DRG neurons of GAP-43 mRNA. We show moreover that failure of re-innervation does not result in a maintenance of GAP-43 mRNA in axotomized motor neurons.
authors.affiliation: Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: M S
authors.initials: MS
authors.lastname: Chong
authors.forename: M
authors.initials: M
authors.lastname: Fitzgerald
authors.forename: J
authors.initials: J
authors.lastname: Winter
authors.forename: M
authors.initials: M
authors.lastname: Hu-Tsai
authors.forename: P C
authors.initials: PC
authors.lastname: Emson
authors.forename: U
authors.initials: U
authors.lastname: Wiese
authors.forename: C J
authors.initials: CJ
authors.lastname: Woolf