Nerve fiber composition of the intracranial portion of the oculomotor, trochlear, and abducens nerves in the sheep

In the present investigation, the fiber content and the diameter spectra of the intracranial portion of the three oculomotor nerves (oculomotor, troch lear, and abducens nerves) were analysed in sheep by light and electron mic roscopy. It was determined that up to 14.98% of fibers in the oculomotor ne rve, 17.01% in the trochlear nerve, and 11.87% in the abducens nerve were u nmyelinated. The myelinated fibers showed a bimodal distribution in their s ize spectrum in all three nerves, with a majority of large myelinated axons , but a considerable proportion of small myelinated fibers, as well. The se nsory function of the unmyelinated fibers present in the three oculomotor n erves is discussed also on the basis of our previous morphofunctional inves tigations. Anat Rec 260:294-298, 2000. (C) 2000 Wiley-Liss, Inc.