Eye Movements, Strabismus, Amblyopia, and Neuro-Ophthalmology A Perioculomotor Nitridergic Population in the Macaque and Cat

METHODS. The oculomotor complex was investigated in monkeys and cats by use of histochemistry to demonstrate nicotinamide adenine dinucleotide phosphate diaphorase positive (NADPHdþ) cells and antibodies to localize neuronal nitric oxide synthase positive (NOSþ) cells. In some cases, wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) was injected into extraocular muscles to allow comparison of retrogradely labeled and NADPHdþ cell distributions. RESULTS. The distribution of the NADPHdþ and NOSþ neurons did not coincide with that of preganglionic and extraocular motoneurons in the oculomotor complex. However, labeled perioculomotor neurons were observed. Specifically, in monkeys, they lay in an arc that extended from between the oculomotor nuclei into the supraoculomotor area (SOA). Comparison of WGA-HRP–labeled medial and superior rectus motoneurons with NADPHd staining confirmed that the distributions overlapped, but showed that the Cand S-group cells were not NADPHdþ. This suggested that NADPHdþ cells are part of the centrally projecting Edinger-Westphal population (EWcp). Examination of the NADPHdþ cell distribution in the cat showed that these cells were indeed found primarily within its well-defined EWcp.