Abstract:

Descending segments of the tectospinal projections in the spinal cord were retrogradely traced by unilateral injection of HRP into different levels of the spinal cord, including the cervical,thoracic and lumbar segments.Experimental results showed that the labeled neurons in the superior colliculus were constantly seen in those animals, in which the upper cervical segments(C_2,3)were injected. No labeled neurons could be found in those cases injected in the cervical enlargement, the thoracic and lumbar segments. All labeled neurons were distributed in the stratum griseum intermediale and the stratum griseum profundum of the caudolateral parts on the side contralateral to the injection,and more labeled neurons were seen in the stratum griseum profundum.This study have suggested that tectospinal tracts project to the upper cervical segments.

Key words: superior colliculus, tectospinal tracts, spinal cord, HRP, rabbit