LOCALIZATION OF PREGANGLIONIC NEURONS OF THE ACCESSORY CILIARY GANGLION IN THE MIDBRAIN - HRP AND WGA-HRP STUDIES IN THE CAT

Localization of preganglionic neurons of the accessory ciliary ganglio n (ACG), including ectopic intraocular ganglion cells, was investigate d in the cat with the aid of horseradish peroxidase (HRP) and HRP-conj ugated wheat germ agglutinin (WGA-HRP) methods. When HRP or WGA-HRP wa s injected into the anterior and posterior chambers of the eye, no ret rogradely labeled cells were found in the visceral oculomotor nuclei, although most neurons of the ACG and the main ciliary ganglion (CG) we re intensely labeled. When a microsyringe needle was inserted into the ciliary body, the tracer diffused into the suprachoroid lamina and th e intraocular ganglion cells, and a small number of labeled neurons ap peared in the midplane between each side of the somatic oculomotor nuc lei. After injection into the ACG, many labeled neurons were observed in the anteromedian nucleus, Edinger-Westphal nucleus, and midplane be tween the somatic oculomotor nuclei, their ventral continuations of th e ventral tegmental area, and the periaqueductal gray. HRP/WGA-HRP inj ection into the CG labeled cells in all these areas and in the lateral border zones of the anteromedian, Edinger-Westphal and somatic oculom otor nuclei, and their ventral continuations of the ventral tegmental area. These findings indicate that the visceral oculomotor neurons whi ch project to the ACG tend to be located more medially than those to t he CG. (C) 1994 Wiley-Liss, Inc.