THE SITE OF THE ORIGIN AND TERMINATION OF THE PROPRIOSPINAL TRACT IN THE RABBIT——A HRP STUDY / 解剖学报

ABSTRACT

HRP was injected into C_6, C_7, L_5, L_6 or T_(5～7) spinal gray. The retrogradely labeled cells and anterogradly labeled terminal arborizations were traced in L_5 and T_5 in cervical injection cases, C_5 and T_5 in lumbar cases, and C_5, L_5 in thoracic cases.Large amount of labeled cell were consistently found in laminae Ⅶ (including the lateral horn of the thoracic cord) and Ⅷ, next numerous in lamina Ⅴ and Ⅹ region. Lamina Ⅰ was found labeled in the cervical and lumbar cord, but virtually not found in the thoracic cord. Labeled cells were few and inconsistent in laminae Ⅳ and Ⅵ. A few labeled lamina Ⅸ cells could be found in the thoracic cord, only occasionally in the lumbar cord, but could not be found in the cervical cord. Laminae Ⅱ and Ⅲ were free from labeled cells in all cases. The labeled terminal arborizations were more widespread and could be found in practically every lamina, being densest in region Ⅹ, laminae Ⅶ (including the lateral horn of the thoracic cord) and Ⅷ. In lumbar injection cases a prominent plexus of labeled terminal arborization could be seen in the ventrolateral part of the C_5 ventral horn. Corresponding plexus was not found in the lumbar cord in cervical injection cases.Some labeled terminal arborizations were found in close approximation to or overlapping with labeled cells or unlabeled motor neurons.These results imply that (1) The occurance of labeled cells and labeled terminal arborizations in the lateral part of lamina Ⅶ (lateral horn) suggests that intersegmental connection is related to visceral activities as well as somatic ones. (2) Labeled cells were consistently found in region Ⅹ which was also the area of dense labeling of terminal arborization, suggesting that this region plays a remarkable role in intersegmental connection. (3) Long ascending bundle connects the lumbar enlargement with the ventrolateral part of the motor neurons directly. (4) The close approximation of labeled terminal arborization and labeled cells signifies direct intersegmental feedback circuit.