The motoneurons innervating the musculus levator palpebrae superiors in the monkey, cat and rabbit

The motoneurons innervating the musculus levator palpebrae superioris (LPS) of the monkey, the cat and the rabbit were studied using horseradish peroxidase (HRP). Furthermore, LPS motoneurons of the cat and rabbit were studied by the double-labeling method using two fluorescent dyes as retrograde neuronal tracers. After injection of HRP into the right LPS of the monkey and the cat, HRP-labeled neurons were found only in the central caudal nucleus with contralateral preponderance. In contrast, after HRP injection into the right LPS of the rabbit, HRP-labeled neurons were found only in the contralateral oculomotor nucleus. In the double-labeling study, after injection of fast blue (FB) into the right LPS and diamidino yellow dihydrochloride (DY) into the left LPS of the cat and the rabbit, no double-labeled neurons were noted in the central caudal nucleus of the cat nor in the oculomotor nucleus of the rabbit, although double-labeled neurons were identified in the central caudal nucleus of the monkey in our previous study. Cross-innervation was confirmed in the mammals lower than the monkey.