title: Differential distribution of growth associated protein (GAP-43) in the motor nuclei of the adult rat conus medullaris.
abstract: GAP-43 is normally produced by neurons during developmental growth and axonal regeneration, but it is also expressed in specific regions of the normal adult nervous system. We studied the protein expression of GAP-43 within the conus medullaris portion of the spinal cord in adult male rats. Immunohistochemistry for choline acetyltransferase (ChAT) was first performed to identify specific efferent autonomic and motor nuclei in lumbosacral segments of the spinal cord. Adjacent sections were then processed for GAP-43 immunoreactivity (IR). We show GAP-43 IR in the superficial portion of the dorsal horn, the intermediolateral nucleus, and the dorsal commissural tract. We also demonstrate a differential distribution of GAP-43 IR between different motor nuclei of the conus medullaris. Using densitometry, the most prominent GAP-43 IR was detected in the dorsolateral and dorsomedial motor nuclei, which represent the human Onuf's nucleus homologue. Confocal microscopy of double immunofluorescent labeling for ChAT and GAP-43 demonstrate GAP-43 IR in the neuropil of the autonomic and motor nuclei, and many of the GAP-43 IR arbors are in close apposition with the efferent cholinergic neurons. We note that the efferent neurons of both the autonomic and somatic nuclei, which are ultimately responsible for the integrated normal control of the lower urinary tract, bowel and sexual functions, are heavily innervated by GAP-43 enriched projections. We speculate that these functionally related neurons retain a physiological GAP-43-associated synaptic plasticity throughout adult life.
authors.affiliation: Department of Neurology and Brain Research Institute, David Geffen School of Medicine at UCLA, 710 Westwood Plaza, Los Angeles, CA 90095-1769, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Warner
authors.forename: Dustin Z
authors.initials: DZ
authors.lastname: Deyoung
authors.forename: Thao X
authors.initials: TX
authors.lastname: Hoang
authors.forename: Brett T
authors.initials: BT
authors.lastname: Franchini
authors.forename: Ulf
authors.initials: U
authors.lastname: Westerlund
authors.forename: Leif A
authors.initials: LA
authors.lastname: Havton
mesh_terms: D000818:Animals; D019922:GAP-43 Protein / Q000032:analysis* / Q000096:biosynthesis*; D008297:Male; D020671:Posterior Horn Cells / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D019922:GAP-43 Protein