van Ham J J, Yeo C H
Department of Anatomy and Developmental Biology, University College London, United Kingdom.
Exp Neurol. 1996 Dec;142(2):244-57. doi: 10.1006/exnr.1996.0195.
The rabbit nictitating membrane and eyeblink response is widely used in studies of classical conditioning. Eyeblinks involve coordinated activation of the orbicularis oculi motoneurons (OOcVII) and accessory abducens motoneurons (AccVI) which close the external eyelids and nictitating membrane, respectively, and inhibition of levator palpebrae motoneurons (LPIII) whose activity raises the upper eyelid. The identification of blink interneurons that may coordinate these responses is an important step in the analysis of mechanisms supporting eyeblink conditioning as they are likely to receive convergent inputs from circuitry associated with learned as well as unlearned responses. We first investigated the distribution of OOcVII motoneurons in the facial nucleus and LPIII motoneurons in the oculomotor nucleus by retrograde tracing of wheat germ-agglutinated horseradish peroxidase (WGA-HRP) injected into the appropriate muscles. We then used an anterograde tracing method to locate trigeminal and paratrigeminal inputs to OOcVII, to AccVI nucleus, and to LPIII. Injections of WGA-HRP were placed into the principal trigeminal nucleus (Vp) and into all divisions of the spinal trigeminal nucleus. We found an area in Vp and the adjacent rostral parts of pars oralis of the spinal trigeminal nucleus that gave clear projections to OOcVII and AccVI motoneurons and adjacent to LPIII motoneurons in the contralateral oculomotor nucleus. We suggest that neurons in this premotor blink area in rabbits can coordinate learned and reflex blink responses involving the external eyelids and the nictitating membrane. In addition, there are direct projections from the pars interpolaris and pars caudalis of the spinal trigeminal nucleus to the facial nucleus that may mediate short latency responses of the external eyelid orbicularis oculi muscle alone.
兔瞬膜和眨眼反应在经典条件反射研究中被广泛应用。眨眼涉及眼轮匝肌运动神经元（OOcVII）和展神经副运动神经元（AccVI）的协同激活，它们分别闭合外眼睑和瞬膜，同时涉及提上睑肌运动神经元（LPIII）的抑制，该神经元的活动会提起上眼睑。识别可能协调这些反应的眨眼中间神经元是分析支持眨眼条件反射机制的重要一步，因为它们可能从与学习和非学习反应相关的神经回路接收汇聚输入。我们首先通过将小麦胚凝集辣根过氧化物酶（WGA-HRP）逆行追踪注入适当肌肉，研究了面神经核中OOcVII运动神经元和动眼神经核中LPIII运动神经元的分布。然后我们使用顺行追踪方法来定位三叉神经和三叉旁神经到OOcVII、AccVI核和LPIII的输入。将WGA-HRP注射到三叉神经主核（Vp）和脊髓三叉神经核的所有分区。我们在Vp和脊髓三叉神经核口部相邻的 Rostral 部分发现了一个区域，该区域向OOcVII和AccVI运动神经元发出清晰的投射，并与对侧动眼神经核中的LPIII运动神经元相邻。我们认为，兔的这个运动前眨眼区域中的神经元可以协调涉及外眼睑和瞬膜的学习和反射性眨眼反应。此外，脊髓三叉神经核的极间部和尾侧部对面神经核有直接投射，这可能单独介导外眼睑眼轮匝肌的短潜伏期反应。
