Neuronal mechanism generating vertical eye position signals.

前庭核（VN）和Cajal间质核（INC）含有与垂直眼运动相关的神经元。为了检查两个核之间可能的相互作用，在警觉的猫身上研究了INC神经元向VN的投射和前庭神经元对这些神经元的输入。我们测试了62个与垂直眼位相关的INC神经元对同侧视神经网络刺激的反应。41个神经元具有向下方向，21个神经元具有向上方向（分别称为向下和向上神经元）。41个下行神经元中有13个在同侧视神经网络以36 ~ 220 muA的阈值刺激后被反向激活。21个向上的神经元均未出现逆行反应。组织学研究表明，刺激部位在vth核水平的VN腹侧。所有由VN反向激活的下向INC神经元在失突触潜伏期（1.3 ~ 2.0 msec）对对侧前庭神经的刺激有正向反应。我们认为，携带垂直眼位信号的视神经网络次级神经元与对侧向下的INC神经元建立兴奋性连接，后者反过来向视神经网络发送信号。这条神经通路可能是负责产生垂直眼位置信号的神经回路的重要组成部分。

The vestibular nucleus (VN) and the interstitial nucleus of Cajal (INC) contain neurons with activity related to vertical eye movement. To examine a possible interaction between the two nuclei, projection of INC neurons to VN and vestibular input to these neurons were studied in the alert cat.Sixty-two INC neurons with activity related to vertical eye position were tested for the response to stimulation of the ipsilateral VN. Forty-one had a downward and 21 an upward on-direction (to be called downward and upward neurons, respectively). Thirteen of 41 downward neurons were antidromically activated following stimulation of the ipsilateral VN with thresholds 36 to 220 muA. None of 21 upward neurons showed antidromic responses. Histological study showed that the stimulation sites had been in the ventral part of VN at the level of the Vlth nucleus. All the downward INC neurons antidromically activated from VN responded orthodromically to stimulation of the contralateral vestibular nerve at disynaptic latencies (1.3 to 2.0 msec). We suggest that secondary VN neurons carrying vertical eye position signals make excitatory connections with contralateral downward INC neurons which in turn send the signal ipsilaterally to VN. This neural pathway may form an important part of the neural circuitry responsible for the generation of vertical eye position signals.