Central pupillary light reflex circuits in the cat: II. Morphology, ultrastructure, and inputs of preganglionic motoneurons.
Preganglionic motoneurons supplying the ciliary ganglion control lens accommodation and pupil diameter. In cats, these motoneurons make up the preganglionic Edinger-Westphal population, which lies rostral, dorsal, and ventral to the oculomotor nucleus. A recent cat study suggested that caudal motoneurons control the lens and rostral motoneurons control the pupil. This led us to examine the morphology, ultrastructure, and pretectal inputs of these populations. Preganglionic motoneurons retrogradely labeled by introducing tracer into the cat ciliary ganglion generally fell into two morphologic categories. Fusiform neurons were located rostrally, in the anteromedian nucleus and between the oculomotor nuclei. Multipolar neurons were found caudally, dorsal and ventral to the oculomotor nucleus. The dendrites of preganglionic motoneurons within the anteromedian nucleus crossed the midline, providing a possible basis for consensual responses. Ultrastructurally, several different classes of synaptic profiles contact preganglionic motoneurons, suggesting that their activity may be modified by a variety of inputs. Furthermore, there were differences in the synaptic populations contacting the rostral vs. caudal populations, supporting the contention that these populations display functional differences. Anterogradely labeled pretectal terminals were observed in close association with labeled preganglionic motoneurons, particularly in the rostral population. Ultrastructural analysis revealed that these terminals, packed with clear, spherical vesicles, made asymmetric synaptic contacts onto motoneurons in the rostral population, indicating that these cells serve the pupillary light reflex. Thus, the preganglionic motoneurons found in the cat display morphologic, ultrastructural, and connectional differences suggesting that this rostral preganglionic population is specialized for pupil control, whereas more caudal elements control the lens.
['Sun|Wensi|W|', 'May|Paul J|PJ|']
D000818:Animals D002415:Cats D065839:Edinger-Westphal Nucleus D005260:Female D005726:Ganglia, Parasympathetic D008297:Male D008854:Microscopy, Electron D009046:Motor Neurons D009847:Olivary Nucleus D010784:Photomicrography D066250:Pretectal Region D012025:Reflex, Pupillary D012160:Retina D013569:Synapses D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
ciliary ganglion lens pupil Edinger-Westphal oculomotor parasympathetic