This cranial nerve controls the lateral movement of the eye. The abducens nerve innervates the lateral rectus extraocular muscle. The abducens motor nerve nucleus is composed of two divisions, the rostral division and the caudal division. Both divisions lie ventrally within the medulla oblongata at mid cerebellar regions. The caudal and rostral nerve roots leave the medulla oblongata and then fuse together and course rostrally once they are outside the brainstem.

Both parts of the abducens motor nerve nucleus are labelled with choline acetyltransferase (ChAT) the acetylcholine synthesising enzyme indicating that this nucleus forms part of the cholinergic system in zebrafish (Mueller et al., 2004).

Development

The isl1 transgene used to visualise most cranial nerves does not label abducens motor neurons (Higashijima et al., 2000). Abducens motor neurons are located in r5 and r6 in zebrafish (Moens et al., 1996). Somatic abducens motor neurons arise from olig2+ neuroepithelial precursors in rhombomeres r5 and r6 (Zannino & Appel., 2009).


Key Publications

Clark, C., Austen, O., Poparic, I., and Guthrie, S. (2013)
alpha2-Chimaerin Regulates a Key Axon Guidance Transition during Development of the Oculomotor Projection.
The Journal of neuroscience. 33(42):16540-16551.

Thomas Mueller, Philippe Vernier, Mario F. Wullimann
The adult central nervous cholinergic system of a neurogenetic model animal, the zebrafish Danio rerio
Brain Research 1011 (2004) 156–169

Asakawa K, Kawakami K.
Protocadherin-Mediated Cell Repulsion Controls the Central Topography and Efferent Projections of the Abducens Nucleus.
Cell Rep. 2018 Aug 7;24(6):1562-1572. doi: 10.1016/j.celrep.2018.07.024.

DA. Zannino & B Appel
Olig2+ Precursors Produce Abducens Motor Neurons and Oligodendrocytes in the Zebrafish Hindbrain
Journal of Neuroscience 25 February 2009, 29 (8) 2322-2333;
DOI: https://doi.org/10.1523/JNEUROSCI.3755-08.2009

Moens CB, Yan YL, Appel B, Force AG, Kimmel CB (1996)
valentino: a zebrafish gene required for normal hindbrain segmentation.
Development 122:3981–3990.