McCrea R A, Strassman A, Highstein S M
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
J Comp Neurol. 1987 Oct 22;264(4):571-94. doi: 10.1002/cne.902640409.
The morphology of 35 vestibular neurons whose firing rate was related to vertical eye movements was studied by injection of horseradish peroxidase intracellularly into physiologically identified vestibular axons in alert squirrel monkeys. The intracellularly injected cells were readily classified into four main groups. One group of cells, down position-vestibular-pause neurons (down PVPs; N = 12), increased their firing rate during downward eye positions, paused during saccades, and were located in the medial vestibular nucleus (MV) and the adjacent ventrolateral vestibular nucleus (VLV). They had axons that crossed the midline and ascended in the medial longitudinal fasciculus (MLF) to terminate in the trochlear nucleus, the lateral aspect of the caudal oculomotor nucleus, and the dorsal aspect of the rostral oculomotor nucleus. A second group of cells (N = 15) were also located in the MV and VLV, but increased their firing rate during upward eye positions, and paused during saccades. These cells had axons that crossed the midline and ascended in the contralateral MLF to terminate in the medial aspect of the oculomotor nucleus. A third group of cells (N = 4) were located in the superior vestibular nucleus, generated bursts of spikes during upward saccades, and increased their tonic firing rate during upward eye positions. These cells had axons that ascended laterally to the ipsilateral MLF to terminate in regions of the trochlear and oculomotor nuclei similar to those in which down PVPs terminated. A fourth group of cells (N = 4), located in the VLV, had axons that projected to the spinal cord, although they had firing rates that were significantly correlated with vertical eye position. Electrical stimulation of the vestibular nerve evoked spikes at monosynaptic latencies in each of the above classes of cells, six of which were injected with horseradish peroxidase. Each group of cells had collateral projections to other areas of the brainstem. Some of the neurons that projected to the contralateral trochlear and oculomotor nuclei had collaterals that crossed the midline to terminate in the oculomotor nucleus ipsilateral to the soma, and some gave rise to small collaterals that terminated in the abducens nucleus. Other areas of the brainstem that received collateral inputs from neurons projecting to oculomotor and trochlear nuclei included the interstitial nucleus of Cajal, the caudal part of the dorsal raphe nucleus, the nucleus raphe obscurus, Roller's nucleus, the intermediate and caudal interstitial nuclei of the MLF, and the nucleus prepositus.
通过将辣根过氧化物酶细胞内注射到警觉松鼠猴体内经生理学鉴定的前庭轴突中，研究了35个放电频率与垂直眼动相关的前庭神经元的形态。细胞内注射的细胞很容易分为四大类。一类细胞，即向下位置-前庭-暂停神经元（向下PVP；N = 12），在向下眼位时放电频率增加，在扫视时暂停，位于内侧前庭核（MV）和相邻的腹外侧前庭核（VLV）。它们的轴突穿过中线并在内侧纵束（MLF）中上升，终止于滑车神经核、尾侧动眼神经核的外侧以及头侧动眼神经核的背侧。第二类细胞（N = 15）也位于MV和VLV，但在向上眼位时放电频率增加，在扫视时暂停。这些细胞的轴突穿过中线并在对侧MLF中上升，终止于动眼神经核的内侧。第三类细胞（N = 4）位于上前庭核，在向上扫视时产生一连串的尖峰，并在向上眼位时增加其紧张性放电频率。这些细胞的轴突向同侧MLF外侧上升，终止于滑车神经核和动眼神经核的区域，类似于向下PVP终止的区域。第四类细胞（N = 4）位于VLV，其轴突投射到脊髓，尽管它们的放电频率与垂直眼位显著相关。前庭神经的电刺激在上述每一类细胞中以单突触潜伏期诱发尖峰，其中六个细胞注射了辣根过氧化物酶。每一组细胞都有侧支投射到脑干的其他区域。一些投射到对侧滑车神经核和动眼神经核的神经元有穿过中线的侧支，终止于与胞体同侧的动眼神经核，一些产生小侧支，终止于展神经核。接受投射到动眼神经核和滑车神经核的神经元侧支输入的脑干其他区域包括 Cajal间质核、背侧中缝核的尾部、中缝隐核、Roller核、MLF的中间和尾部间质核以及前庭前核。
