Individual axon morphology and thalamocortical topography in developing rat somatosensory cortex.

摘要: The morphology of individual thalamocortical axons in developing rat primary somatosensory cortex was studied using lipophilic tracers. Anterograde labeling with dyes demonstrated a topographical organization projections exiting the thalamus as early embryonic day (E)16; retrograde studies topography these they reached E18. At E17, course tangentially within intermediate zone and turn or branch near deepest layer (layer VIb), suggesting presence guidance cues this region. Axons appear to grow progressively layers VIb VIa during following days; may give rise radially directed branches. Individual steadily into cortex, leading front at transition between cortical plate (CP) differentiating layers. birth (PO), extend through V emit branches layers; some reach CP. By P1, IV has begun differentiate begin form few simple vicinity cells. Over ensuing week, generate more IV, but tangential extent axon arbors does not exceed width barrel. P7, overlap barrel clusters, span cluster. These observations indicate that thalamic afferents develop by progressive growth remain spatially restricted, rather than overbranching retracting arbors. © 1996 Wiley-Liss, Inc.