抄録
We showed the rat corticospinal (CS) synapses were formed all the gray matter at P6-7; but those in the ventrolateral area were eliminated from P8 to P10. However, after this synapse elimination, the "second wave" of the CS innervation arrived at P12: CS terminals again increase on the ventral and also dorsal side. In this study, the CS synaptic responses were directly shown in the acute cervical cord slices by optical imaging with the voltage sensitive dye. The ventralmost part of posterior funiculus was stimulated to activate CS axons and the response signal was recorded. The responses were disappeared after an electrolytic lesion made by DC current. The optical response in the VL area once peaked at P6-7, but reduced at P10, and increased again from P15. To study developmental change in corticoceptive spinal neurons, spinal cord cells were whole-cell patch clamped and electrophysiological properties were studied. CS-EPSC-positive cells were labeled with NeurobiotinTM, which were later reconstructed on the two-dimensional plain by camera lucida drawing. Responsive neurons are widely distributed in the P6-7 neonates from the laminae III to IX, but neurons in the laminae IX became unresponsive at P10. The majority of the ventral neurons have multipolar, long and smooth dendrites with large (20-30 μm in the diameter) somata showing "repetitive" (trains of multiple spikes) or "phasic"(decreasing spike trains) firin. On the other hand, most of dorsal neurons have smaller (10-20 μm) somata and multipolar branches, and they have "repetitive", "phasic", or "delayed onset" firing. [J Physiol Sci. 2008;58 Suppl:S120]
