SUPERIOR CERVICAL GANGLIONECTOMY IN MONKEYS - LIGHT AND ELECTRON-MICROSCOPY OF THE ANTERIOR EYE SEGMENT

Morphological changes in the anterior eye segment of eight cynomolgus monkeys were investigated 2 days to 2.2 years after unilateral surgica l superior cervical ganglionectomy (SCGx). SCGx was confirmed by histo logic examination of the excised surgical specimen and persistent ipsi lateral miosis. In four short-term monkeys (2, 4, 7 and 11 days), iris , ciliary muscle and trabecular meshwork were studied by electron micr oscopy, In the other four longer-term monkeys (3 week, 4 week, 5 week, 22 year) the anterior eye segment was investigated with tyrosine hydr oxylase immunohistochemistry (TH-IR) and catecholamine fluorescence (C F). Electron microscopy of experimental eyes showed characteristic sig ns of Wallerian degeneration in numerous nerve fibers and terminals in the iris, but to a lesser extent in the ciliary muscle and the trabec ular meshwork, TH-IR and CF showed marked interindividual differences. In all experimental eyes, there was a marked reduction, but never a c omplete absence of adrenergic nerves in the iris. In two animals (4 we ek and 2.2 years), the adrenergic innervation of the ciliary body and the chamber angle was similarly reduced. In contrast, in the experimen tal eyes of the other two animals (3 and 5 weeks), changes in adrenerg ic innervation to the ciliary body and chamber angle were minimal or a bsent. The results indicate that following apparently complete SCGx in the cynomolgus monkey, reduction of adrenergic innervation to the iri s as evidenced by pupillary physiology, electron microscopy, TH-IR and CF does not guarantee reduction in adrenergic innervation to the cili ary body and trabecular meshwork, SCGx may not extirpate all third ord er sympathetic neurons in the distal stump, or there may be a signific ant contribution of accessory ganglion cells to the adrenergic innerva tion of the anterior eye segment. (C) 1997 Academic Press Limited.