Localization of motoneurons innervating the extraocular muscles of the sheep by retrograde fluorescent tracers.

Abstract

Retrograde transport of the fluorescent tracers Fast blue, Evans blue, Diamidino yellow dihydrochloride, and Propidium iodide was used to determine the location of the motoneurons innervating the extraocular muscles of the sheep. An extensive superposition among the motor pools of the oculomotor nucleus (ON) has been observed. In the rostral third of the ON, a considerable merging occurs between obliquus ventralis and rectus medialis motoneurons and also between rectus ventralis and rectus medialis motoneurons. In the middle third of the ON, rectus dorsalis and levator palpebrae superioris motoneurons are intermingled with each other, and also with obliquus ventralis motoneurons dorsally and with rectus medialis motoneurons ventrally. The rostral portion of the trochlear nucleus overlaps with the caudal pole of the ON. The motoneurons innervating the obliquus dorsalis muscle are mainly contralateral with few ipsilateral exceptions. The retractor bulbi muscle receive the innervation by both the abducens and accessory abducens nuclei.