The Journal of Neuroscience, 1999, 19:RC22:1-5
RAPID COMMUNICATION
Growth-Associated Protein 43 Is Located in Type I Corticothalamic
Terminals in the Cat Visual Thalamus
Martha E.
Bickford
Department of Anatomical Sciences and Neurobiology, University of
Louisville, School of Medicine, Louisville, Kentucky 40292
Growth-associated protein 43 (GAP 43) is a presynaptic protein that
has been proposed to be involved in synaptic plasticity. To determine
the location of GAP 43 within the synaptic circuitry of the thalamus,
immunocytochemical staining for GAP 43 was examined in a relay nucleus,
the dorsal lateral geniculate nucleus (dLGN), and two association
nuclei, the pulvinar nucleus and the lateral subdivision of the lateral
posterior (LP) nucleus. In the dLGN, moderate neuropil staining was
seen in the A laminae, and denser staining was found in the
interlaminar zones and the C laminae. Uniform dense staining of the
neuropil was found in both the pulvinar and LP nuclei. At the
ultrastructural level, the GAP 43 staining was restricted to
small-diameter myelinated axons, thin unmyelinated fibers, and small
terminals that contained densely packed round vesicles (RS profiles)
and made asymmetric synaptic contacts with small-caliber dendrites in
the extraglomerular neuropil. The distribution of immunocytochemical
label within the visual thalamus suggests that GAP 43 is confined to
type I corticothalamic terminals and axons that originate from
extrastriate cortical areas. These results also suggest that in both
relay and association nuclei GAP 43 may be used to augment the cortical
control of thalamic activity. In addition, these results underscore the
distinction between the small type I corticothalamic terminals, which
appear to contain GAP 43 throughout the visual thalamus, and the
large type II corticothalamic terminals that, like the type II retinal
terminals in the dLGN, do not contain GAP 43.
Key words:
lateral geniculate nucleus; pulvinar nucleus; lateral
posterior nucleus; relay; association; ultrastructure; synaptic
plasticity
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