The peripheral course of the axons innervating the medial rectus muscle within the subarachnoid portion of the oculomotor nerve.

There is clinical evidence of topographic localisation of fibres within the oculomotor nerve. It is generally accepted that the pupillomotor fibres have a localised course within the dorsomedial periphery of the subarachnoid portion. However, the precise course of the individual groups of axons innervating each muscle has not been examined in detail. In this study the course of the axons innervating the medial rectus muscle was investigated in the subarachnoid portion of the oculomotor nerve of the rat. The medial rectus muscle was injected with horseradish peroxidase until it was fully infiltrated. The subarachnoid portion of the oculomotor nerve was removed and sectioned longitudinally in the sagittal plane. Sections were reacted with tetramethylbenzidine as a chromogen. Labelled axons were found to be localised in the ventral part of the subarachnoid portion of the nerve.