Accessory abducens nucleus and its relationship to the accessory facial and posterior trigeminal nuclei in cat

Abstract

Retrograde transport of HRP by the abducens nerve results in the labelling of its principal nucleus and, in addition, a second nucleus about 2.5 mm ventrolateral to the principal nucleus. The presence of this second or accessory nucleus of the abducens in a mammal confirms the observations of several Nineteenth Century anatomists and rebuts the conclusions of more recent investigators who argued that the nucleus was allied instead to the facial or trigeminal nerves. The same HRP technique applied to the facial or trigeminal nerves shows that the accessory nucleus of the abducens is in the same parasagittal plane as the accessory nucleus of the facial nerve and the most caudal cells of the motor trigeminal nucleus. The accessory abducens and accessory facial nuclei fall in a ventrocaudal to dorsorostral line between the principal nucleus of the facial and the motor nucleus of the trigeminal with the accessory abducens just caudal and ventral to the accessory facial.