Arbeitsgruppe Neurosensorik/Animal Navigation, Institut für Biologie und Umweltwissenschaften, University of Oldenburg, D-26111 Oldenburg, Germany.
Proc Natl Acad Sci U S A. 2010 May 18;107(20):9394-9. doi: 10.1073/pnas.0907068107. Epub 2010 May 3.
The upper beak of birds, which contains putative magnetosensory ferro-magnetic structures, is innervated by the ophthalmic branch of the trigeminal nerve (V1). However, because of the absence of replicable neurobiological evidence, a general acceptance of the involvement of the trigeminal nerve in magnetoreception is lacking in birds. Using an antibody to ZENK protein to indicate neuronal activation, we here document reliable magnetic activation of neurons in and near the principal (PrV) and spinal tract (SpV) nuclei of the trigeminal brainstem complex, which represent the two brain regions known to receive primary input from the trigeminal nerve. Significantly more neurons were activated in PrV and in medial SpV when European robins (Erithacus rubecula) experienced a magnetic field changing every 30 seconds for a period of 3 h (CMF) than when robins experienced a compensated, zero magnetic field condition (ZMF). No such differences in numbers of activated neurons were found in comparison structures. Under CMF conditions, sectioning of V1 significantly reduced the number of activated neurons in and near PrV and medial SpV, but not in lateral SpV or in the optic tectum. Tract tracing of V1 showed spatial proximity and regional overlap of V1 nerve endings and ZENK-positive (activated) neurons in SpV, and partly in PrV, under CMF conditions. Together, these results suggest that magnetic field changes activate neurons in and near the trigeminal brainstem complex and that V1 is necessary for this activation. We therefore suggest that V1 transmits magnetic information to the brain in this migratory passerine bird.
鸟类的上喙包含假定的磁感受铁磁结构，由三叉神经（V1）的眼支神经支配。然而，由于缺乏可复制的神经生物学证据，三叉神经参与磁感觉在鸟类中尚未得到普遍接受。我们使用针对 ZENK 蛋白的抗体来指示神经元的激活，在此记录到可靠的磁激活在三叉神经脑桥复合体的主要（PrV）和脊髓束（SpV）核内和附近的神经元，这些核代表已知接收三叉神经初级输入的两个脑区。当欧洲知更鸟（Erithacus rubecula）经历磁场每 30 秒变化一次持续 3 小时的周期（CMF）时，PrV 和内侧 SpV 中的激活神经元数量明显多于经历补偿零磁场条件（ZMF）时。在比较结构中没有发现激活神经元数量的差异。在 CMF 条件下，V1 的切断显著减少了 PrV 和内侧 SpV 中以及附近的激活神经元的数量，但在外侧 SpV 或视顶盖中没有减少。V1 的追踪显示，在 CMF 条件下，V1 神经末梢和 SpV 中的 ZENK 阳性（激活）神经元在空间上接近并且区域重叠，在 PrV 中部分重叠。这些结果表明磁场变化激活了三叉神经脑桥复合体中的神经元，并且 V1 是这种激活所必需的。因此，我们认为 V1 在这种迁徙雀形目鸟类中向大脑传递磁信息。
