Eaj. Joosten et al., TRANSIENT PROJECTIONS FROM RAT OCCIPITAL CORTEX ARE ABLE TO RESPOND TO A SPINAL TARGET-DERIVED DIFFUSIBLE FACTOR IN-VITRO, Neuroscience letters, 164(1-2), 1993, pp. 85-88
Layer V pyramidal neurons in the occipital part of the rat cerebral co
rtex 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is subsequently withdrawn, while a permanent connection is maintained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 corticospi
nal axons may be due to their inability to respond to target-derived i
nfluences. In the current study we co-cultured explants of the occipit
al cortex and cervical spinal gray matter or tectum in 3-D collagen ge
ls. Directional growth of the cortical axons towards either the cervic
al spinal gray or tectal explant was observed. This indicates that the
failure of neurons located in the occipital cortex to maintain collat
erals 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 ext
rinsic factors.