後半規管入力を受ける前庭脊髄路ニューロンの軸索投射様式

Abstract

Axonal pathways and the projection levels of posterior-semicircular canal (PC)-ac-tivated vestibulospinal neurons were studied in decerebrated and anesthetized cats. The PC nerve was selectively stimulated by bipolar silver electrodes. Two monopolar electrodes were inserted into the lateral vestibulospinal tract (LVST) and medial vestibulospinal tract (MVST) to determine the pathway of axons. Three pairs of similar electrodes were positioned in the C2-3, C7-T1 and T12-L3 segments to examine projection levels. Another monopolar electrode was placed in the oculomotor nuclei to determine whether PC-nerve-activated vestibulospinal neurons s have branches ascending to the oculomotor nuclei.Fifty six neurons were activated orthodromically after PC nerve stimulation. Ten PC-nerve-activated vestibulospinal neurons were also antidromicaly activated from the oculomotor nuclei. All of these vestibulo-oculo-spinal (VOS) neurons descended through the MVST and terminated in the upper cervical segments. Eighteen PC-ner-ve-activated vestibulospinal neurons descended through the LVST, 45% of which reached upper lumber segments. Fourteen vestibulospinal neurons descended through the MVST. Most of these terminated in upper cervical segments. These results suggest that VOS neurons convey posterior semicircular canal signals to both the ocular and neck motor centers, linking eye and head movement.