| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
To advance understanding the functional role of commissural neurons in the generation of alternating left-right hindlimb locomotor rhythm in cats, their distribution and axonal projection in the lumbosacral spinal cord were investigated with a neural tracing technique using a tracer, biotinylated-dextran amine (BDA). Following BDA injections into the left laminae VII-IX at segments L5-6, a large number of neurons were labeled retrogradely in the left and right ventral horn throughout the lumbosacral cord. In laminae VII and IX injections, labeled cells were distributed predominantly in the injection side, while in lamina VIII injection, they were distributed evenly bilaterally. In the latter case, about 40% of all labeled cells were located in the contralateral (right) lamina VIII, where commissural neurons were densely distributed. Following the injection into lamina VIII, commissural axons crossing the midline to the contralateral side were labeled anterogradely. They were divided into two major groups according to their courses in the contralateral white matter. The first group ascended and/or descended mainly in the ventral funiculus and the second one in the ventral to lateral funiculi. Axon collaterals from the former group terminated mainly in lamina VIII, whereas those from the latter one mainly in lamina IX. These findings indicate that lumbar commissural neurons on the left and right sides are tightly connected, and such mutual connection might be well suited to elaborate alternating left-right hindlimb locomotor rhythm. Further, considering that long descending pathways including the reticulospinal and vestibulospinal pathways terminate mainly in lamina VIII and adjacent lamina VII at all spinal cord levels, such descending pathways and commissural neuronal systems as a whole may constitute a unified system which well serve to coordinate interlimb and limb-trunk movements during locomotion.
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