Synaptogenesis in the chick cervical cord and possible initial central pathways from dorsal root fibers to motor...

The early formation of neuronal connections in the cervical cord of the chick embryo was studied by observing axonal courses at stages 24 and 27 with Golgi preparations and the distribution of synapses at stages 22, 25 and 27 with electron microscopy. Early developing interneurons sent their axon to the ventral and lateral funiculi. Synapses were observed in the transit part from ventral to lateral funiculus at stage 22, in the ventral funiculus, the ventral part of the lateral funiculus and the dorsal funiculus at stage 25. It was suggested that the neuronal pathways from dorsal root fibers to motor neurons were first formed at stage 25 with the intervention of interneurons.