Bilateral innervation of the musculus levator palpebrae superioris by single motoneurons in the monkey.

The location of motoneurons innervating the musculus levator palpebrae superioris (LPS) was studied in the monkey (Macaca irus) by using Fast blue (FB) and propidium iodide (PI) as retrograde neuronal tracers. In each monkey, FB was injected into the LPS of one eye and PI into the LPS of the other eye. Neuronal cell bodies labeled with FB and/or PI were seen intermixed bilaterally through the entire rostrocaudal extent of the central caudal nucleus. While single-labeled (70%) cell bodies predominated, many double-labeled (30%) cell bodies were also encountered. Each of the double-labeled neurons was concluded to supply the LPS on both sides by way of axon collaterals.