Central trigeminal and posterior eighth nerve projections in the turtle Chrysemys picta studied in vitro.
Central trigeminal and posterior eighth nerve projections in the turtle Chrysemys picta studied in vitro.
复制标题
体外研究的 Chrysemys picta 龟的中央三叉神经和后第八神经投射。
DOI：
10.1159/000006537
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Keifer,J
中科院分区：
文献类型：
--
作者：
Herrick,JL;Keifer,J
最近的电生理学研究表明，在海龟的刺眼反射的神经相关可以诱发在体外脑干小脑制备电刺激，而不是自然刺激的颅神经。外展神经中记录的放电类似于眼球回缩期间眼外肌的EMG记录，是由施加到同侧三叉神经的短暂电刺激触发的。证据还表明，配对的一秒钟的电刺激施加到后第八神经之前，立即单次电击三叉神经的结果在经典的条件外展神经放电响应于先前的中性第八神经刺激。鉴于这些生理学发现，本研究的目的是检查三叉神经和后第八神经输入的中枢投射，以阐明可能构成体外眨眼反射的解剖学基础和反射条件反射中可能涉及的途径。将神经生物素（NB）或荧光素葡聚糖（FD）加压注射到离体脑干-小脑的三叉神经或后第八神经的切断端。在三叉神经注射后，两种示踪剂在同侧三叉神经核复合体中显示标记。直接投射到同侧的主和副外展肌运动核，表明眨眼反射是单突触。三叉神经轴突也被观察到终止于同侧小脑皮质。第八神经后注射结果显示耳蜗、前庭和三叉神经感觉主核内有轴突投射和终末。在同侧小脑皮质、小脑深核、主外展肌和副外展肌运动核中也观察到终末标记。NB病例的结果表明这种示踪物质的跨神经元转运，而FD病例则没有。目前的研究结果表明，三叉神经和后第八神经输入的会聚发生在同侧小脑皮质，三叉神经感觉主核，和主副外展神经运动核。这些地区的收敛，因此可以被认为是潜在的网站的突触修改在体外研究的条件外展神经反射。
Recent electrophysiological studies in the turtle Chrysemys picta have suggested that a neural correlate of the eye-blink reflex can be evoked in an in vitro brainstem-cerebellum preparation by electrical rather than natural stimulation of the cranial nerves. Discharge recorded in the abducens nerve, which is similar to EMG recordings from extraocular muscles during eye retraction, is triggered by a brief electrical stimulus applied to the ipsilateral trigeminal nerve. Evidence also suggests that pairing a one-second electrical stimulus applied to the posterior eighth nerve immediately prior to a single shock to the trigeminal nerve results in classically conditioned abducens nerve discharge in response to the previously neutral eighth nerve stimulus. In view of these physiological findings, the aim of the present study was to examine the central projections of trigeminal and posterior eighth nerve inputs to elucidate the anatomical substrates that may underlie the in vitro eye-blink reflex and possible pathways involved in reflex conditioning. Neurobiotin (NB) or fluorescein dextran (FD) was pressure injected into the cut end of either the trigeminal or posterior eighth nerve of the in vitro brainstem-cerebellum. Following trigeminal nerve injections, both tracers showed label in the ipsilateral trigeminal nuclear complex. Direct projections to the ipsilateral principal and accessory abducens motor nuclei were observed, suggesting that the eye-blink reflex is monosynaptic. Trigeminal nerve axons were also observed to terminate in the ipsilateral cerebellar cortex. The results of the posterior eighth nerve injections showed axonal projections and terminals in the cochlear, vestibular and principal sensory trigeminal nuclei. Terminal label was also observed in the ipsilateral cerebellar cortex, deep cerebellar nuclei, and in the principal and accessory abducens motor nuclei. Results from the NB cases suggested transneuronal transport of this tracer substance, whereas the FD cases did not. The present findings suggest that convergence of trigeminal and posterior eighth nerve inputs occurs in the ipsilateral cerebellar cortex, the principal sensory trigeminal nucleus, and the principal and accessory abducens motor nuclei. These regions of convergence may therefore be considered as potential sites of synaptic modification during in vitro studies of the conditioned abducens nerve reflex.