title: Corticothalamic cells in layers 5 and 6 of primary and secondary sensory cortex express GAP-43 mRNA in the adult rat.
abstract: The expression of a presynaptic phosphoprotein, growth-associated protein (GAP)-43, is associated with synaptogenesis during development and synaptic remodeling in the adult. This study examined GAP-43 mRNA expression and distribution in primary and secondary areas of visual, auditory, and somatosensory cortex of the adult rat, by in situ hybridization with a digoxigenin-coupled mRNA probe, focusing particularly on the corticothalamic cells in layers 5 and 6. In the six cortical areas studied, GAP-43 mRNA was expressed predominantly in layers 5 and 6 and was greater in secondary than primary areas. There were densely labeled cells in layers 5 and 6 of all areas, which showed a restricted sublaminar distribution in primary areas and more even distribution in secondary areas. Combining retrograde transport of rhodamine beads with in situ hybridization in visual and auditory cortex showed that corticothalamic cells in layers 5 and 6 express GAP-43 mRNA. There are more of these GAP-43 mRNA positive corticothalamic cells in layer 5 of secondary areas than in primary areas. The evidence suggests that in the adult rat, plasticity related to GAP-43 is present in primary and secondary sensory cortex and more so in secondary areas.
authors.affiliation: Department of Anatomy, University of Wisconsin School of Medicine, Madison, Wisconsin 53706, USA. slfeig@wiscmail.wisc.edu
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Feig
mesh_terms: D000818:Animals; D001303:Auditory Cortex / Q000737:chemistry*; D004076:Digoxigenin; D019922:GAP-43 Protein / Q000032:analysis* / Q000235:genetics; D017403:In Situ Hybridization; D008297:Male; D009434:Neural Pathways / Q000737:chemistry; D017966:Pyramidal Cells / Q000737:chemistry*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020318:Rats, Long-Evans; D013003:Somatosensory Cortex / Q000737:chemistry*; D013788:Thalamus / Q000737:chemistry; D014793:Visual Cortex / Q000737:chemistry*
chemical_list: D019922:GAP-43 Protein; D012333:RNA, Messenger; D004076:Digoxigenin