[The parasympathetic direct pathway from the midbrain to the ciliary muscle in cats and monkeys]

The visceral, namely the parasympathetic component of the oculomotor complex which directly innervates ciliary muscle was investigated using horseradish peroxidase (HRP) in three cats and three monkeys. A unilateral total iridectomy to abolish innervation to the iris was made in all animals. After 1 month to allow fiber degeneration in the iris, HRP was injected into the ciliary muscle of ipsilateral eye. Distribution of the labeled cells at the midbrain and at the ciliary ganglion was examined. Labeled cells were present in the ciliary ganglion and midbrain in all three cats and three monkeys. In the cat, labeled cells were distributed in the Edinger-Westphal (EW) nucleus and the Perlia nucleus. In the monkey, labeled cells were distributed in the anteromedian (AM) nucleus, the EW nucleus and the Perlia nucleus, respectively. Therefore, the existence of a direct parasympathetic pathway from the midbrain to the ciliary muscles was confirmed in these animals. Based on these observations, it is obvious that accommodation of the eye was innervated partly by a direct pathway from the midsagittal region of the parasympathetic neuron of the oculomotor nuclear complex.