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Transient projections from rat occipital cortex are able to respond to a spinal target derived diffusible factor in
E A Joosten1, P R Bär, W H Gispen
1Department of Anatomy and Cell Biology, Georgetown University School of Medicine, Washington, DC.
Abstract:
Layer V pyramidal neurons in the occipital part of the rat cerebral cortex project to both the cervical spinal cord and the tectum early in postnatal development. The occipito-spinal projection is transient and is subsequently withdrawn, while a permanent connection is maintained with the tectum. The withdrawal of the transient occipital corticospinal axons may be due to their inability to respond to target-derived influences. In the current study we co-cultured explants of the occipital cortex and cervical spinal gray matter or tectum in 3-D collagen gels. Directional growth of the cortical axons towards either the cervical spinal gray or tectal explant was observed. This indicates that the failure of neurons located in the occipital cortex to maintain collaterals within the spinal cord in vivo is not due to their inability to respond to a target-derived factor, but must be regulated by other extrinsic factors.