Abstract
Synaptogenesis of the corticospinal axons was studied to examine the formation of neuronal connections of the corticospinal tract in the rat spinal cord of the postnatal period.
Most of the right cerebral hemispheres of the rats at 1,7 and 14 days after birth were destroyed with the electrical generator. At 1,2,3,4,5,6 days after the operation animals were fixed, and the cervical cord was observed using the electron microscope to identify the synaptic connections of the corticospinal axons occurred their degenerated changes.
At 1 day after birth, the corticospinal axons made synaptic connections with small dendrites, somata and axons of neurons in the intermediate zone and posterior horn contralaterally. A few synaptic connections of these axons were found in the same areas ipsilaterally. At 7 days, synaptic connections of the corticospinal axons were mainly found in the contralateral intermediate zone and posterior horn. In these areas various synaptic connections appeared as follows: the corticospinal axon formed synaptic connections not only with a dendrite or a soma, but also with several dendrites or axons. At 14 days, most of corticospinal axons distributed mainly in the posterolateral region of the posterior horn contralaterally, and formed various types of synaptic connections. Some of them were identified as the central axons in the synaptic glomeruli of the substantia gelatinosa. These findings indicate that the corticospinal axon is involved in the sensory system of the rat spinal cord.
