Izawa Yoshiko, Sugiuchi Yuriko, Shinoda Yoshikazu
Dept. of Systems Neurophysiology, Graduate School of Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8519, Japan.
J Neurophysiol. 2007 May;97(5):3696-712. doi: 10.1152/jn.01073.2006.
The neural organization of the pathways from the superior colliculus (SC) to trochlear motoneurons was analyzed in anesthetized cats using intracellular recording and transneuronal labeling techniques. Stimulation of the ipsilateral or contralateral SC evoked excitation and inhibition in trochlear motoneurons with latencies of 1.1-2.3 and 1.1-3.8 ms, respectively, suggesting that the earliest components of excitation and inhibition were disynaptic. A midline section between the two SCs revealed that ipsi- and contralateral SC stimulation evoked disynaptic excitation and inhibition in trochlear motoneurons, respectively. Premotor neurons labeled transneuronally after application of wheat germ agglutinin-conjugated horseradish peroxidase into the trochlear nerve were mainly distributed ipsilaterally in the Forel's field H (FFH) and bilaterally in the interstitial nucleus of Cajal (INC). Consequently, we investigated these two likely intermediaries between the SC and trochlear nucleus electrophysiologically. Stimulation of the FFH evoked ipsilateral mono- and disynaptic excitation and contralateral disynaptic inhibition in trochlear motoneurons. Preconditioning stimulation of the ipsilateral SC facilitated FFH-evoked monosynaptic excitation. Stimulation of the INC evoked ipsilateral monosynaptic excitation and inhibition, and contralateral monosynaptic inhibition in trochlear motoneurons. Preconditioning stimulation of the contralateral SC facilitated contralateral INC-evoked monosynaptic inhibition. These results revealed a reciprocal input pattern from the SCs to vertical ocular motoneurons in the saccadic system; trochlear motoneurons received disynaptic excitation from the ipsilateral SC via ipsilateral FFH neurons and disynaptic inhibition from the contralateral SC via contralateral INC neurons. These inhibitory INC neurons were considered to be a counterpart of inhibitory burst neurons in the horizontal saccadic system.
利用细胞内记录和跨神经元标记技术，在麻醉猫中分析了从上丘（SC）到滑车运动神经元的通路的神经组织。刺激同侧或对侧SC分别在滑车运动神经元中诱发兴奋和抑制，潜伏期分别为1.1 - 2.3毫秒和1.1 - 3.8毫秒，这表明兴奋和抑制的最早成分是双突触的。在两个SC之间的中线横切显示，同侧和对侧SC刺激分别在滑车运动神经元中诱发双突触兴奋和抑制。将小麦胚凝集素结合辣根过氧化物酶应用于滑车神经后经跨神经元标记的运动前神经元主要同侧分布于Forel氏场H（FFH），双侧分布于 Cajal间质核（INC）。因此，我们用电生理学方法研究了SC和滑车核之间这两个可能的中间神经元。刺激FFH在滑车运动神经元中诱发同侧单突触和双突触兴奋以及对侧双突触抑制。同侧SC的预处理刺激促进了FFH诱发的单突触兴奋。刺激INC在滑车运动神经元中诱发同侧单突触兴奋和抑制以及对侧单突触抑制。对侧SC的预处理刺激促进了对侧INC诱发的单突触抑制。这些结果揭示了在扫视系统中从上丘到垂直眼运动神经元的相互输入模式；滑车运动神经元通过同侧FFH神经元从同侧SC接受双突触兴奋，并通过对侧INC神经元从对侧SC接受双突触抑制。这些抑制性INC神经元被认为是水平扫视系统中抑制性爆发神经元的对应物。
