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Horizontal eye movement networks in primates as revealed by retrograde transneuronal transfer of rabies virus: Differences in monosynaptic input to “slow” and “fast” abducens motoneurons
Author(s) -
Ugolini Gabriella,
Klam François,
Doldan Dans Maria,
Dubayle David,
Brandi AnneMarie,
BüttnerEnnever Jean,
Graf Werner
Publication year - 2006
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.21092
Subject(s) - medial longitudinal fasciculus , abducens nucleus , anatomy , reticular formation , oculomotor nucleus , biology , neuroscience , vestibular nuclei , paramedian pontine reticular formation , eye movement , axoplasmic transport , reticular connective tissue , anterograde tracing , nucleus , midbrain , vestibular system , central nervous system
The sources of monosynaptic input to “fast” and “slow” abducens motoneurons (MNs) were revealed in primates by retrograde transneuronal tracing with rabies virus after injection either into the distal or central portions of the lateral rectus (LR) muscle, containing, respectively, “en grappe” endplates innervating slow muscle fibers or “en plaque” motor endplates innervating fast fibers. Rabies uptake involved exclusively motor endplates within the injected portion of the muscle. At 2.5 days after injections, remarkable differences of innervation of slow and fast MNs were demonstrated. Premotor connectivity of slow MNs, revealed here for the first time, involves mainly the supraoculomotor area, central mesencephalic reticular formation, and portions of medial vestibular and prepositus hypoglossi nuclei carrying eye position and smooth pursuit signals. Results suggest that slow MNs are involved exclusively in slow eye movements (vergence and possibly smooth pursuit), muscle length stabilization and gaze holding (fixation), and rule out their participation in fast eye movements (saccades, vestibulo‐ocular reflex). By contrast, all known monosynaptic pathways to LR MNs innervate fast MNs, showing their participation in the entire horizontal eye movements repertoire. Hitherto unknown monosynaptic connections were also revealed, such as those derived from the central mesencephalic reticular formation and vertical eye movements pathways (Y group, interstitial nucleus of Cajal, rostral interstitial nucleus of the medial longitudinal fasciculus). The different connectivity of fast and slow MNs parallel differences in properties of muscle fibers that they innervate, suggesting that muscle fibers properties, rather than being self‐determined, are the result of differences of their premotor innervation. J. Comp. Neurol. 498:762–785, 2006. © 2006 Wiley‐Liss, Inc.