An experimental inquiry into the central source of preganglionic fibers to the chick ciliary ganglion

Abstract

Degenerative changes in the entire third nerve nucleus were studied following selective removal of the ciliary ganglion, usually of the right side, in day-old chicks. The operated animals were allowed to survive three, six, nine, and twelve days after ciliary ganglionectomy. Retrogarde degenerative changes proceed rapidly between three and nine days post-operatively, and are strictly limited to the ipsilateral accessory oculomotor nucleus. The changes are at first observed in the medial division of the accessory oculomotor nucleus, followed by the lateral division of the accessory oculomotor nucleus. By nine days following the operation, both the divisions of the accessory oculomotor nucleus are virtually depleted of almost all neurons. The other components of the oculomotor complex were not affected at any stage by ciliary ganglionectomy. These observations provide conclusive evidence that the accessory oculomotor nucleus is indeed the avian homologue of the Edinger-Westphal nucleus.

Substance P-containing neurons of the avian suprachiasmatic nucleus project directly to the nucleus of Edinger-Westphal.

“…Choroidal neurons receive only boutonal endings while ciliary neurons receive only calyciform endings. As noted, the EW in birds consists of two major subdivisions, EWI and EWm (1). Several lines of evidence argue that the EWl.projects to the ciliary neurons while the EWm projects to the choroidal neurons.…”

“…The nucleus of Edinger-Westphal (EW) is the autonomic parasympathetic subdivision ofthe oculomotor complex (1)(2)(3). In the pigeon, this nucleus is well defined and appears to comprise at least two cytoarchitectonically distinct subdivisions, a medial and a lateral.…”

“…The cells of the medial subdivision of the EW (EWm) are characteristically smaller and more fusiform than the cells of the lateral subdivision of the EW (EWI). Both subdivisions give rise to preganglionic parasympathetic fibers to the ciliary ganglion (1,2,4). The ciliary ganglion, in turn, innervates the sphincter pupillae muscle of the iris, the ciliary body, and the smooth musculature of the choroidal coat of the eye (5).…”

The development of ACh- and GABA-activated currents in embryonic chick ciliary ganglion neurons in the absence of innervation in vivo

“…It is known that following early eye removal, there is almost complete cell loss in the AON by El4 (Cowan and Wenger, 1968; see also Narayanan and Narayanan, 1976). This transneuronal degeneration of the AON suggests that, in our earlier study, eye ablation not only removed the target tissues of the embryonic ciliary ganglion but, after E14, deprived the neurons of their innervation as well, yet ACh-activated currents increased threefold between E 14 and E 18 in these neurons (Engisch and Fischbach, 1990).…”

Development of parvalbumin immunoreactivity in the chick Edinger Westphal nucleus

“…Its development has been studied previously and its physiological functions are known. Edinger Westphal neurons serve as the sole preganglionic input to the ciliary ganglion (Cowan and Wenger, 1968;Narayanan and Narayanan, 1976). Ciliary ganglion neurons in turn project to the iris, ciliary body, and choroidal blood vessels to control pupilloconstriction, accommodation, and choroidal blood flow, respectively (Marwitt et al, 1971;Reiner et al, 1983;Meriney and Pilar, 1987;Fitzgerald et al, 1990).…”