Ptosis in the rat following topically administered 2% epinephrine.

Commercially available 2% epinephrine instilled twice daily in one eye of 15 rats resulted in ptosis after 4 weeks treatment. The ptosis was indistinguishable from that observed following topical treatment with 6-hydroxydopamine 20% and surgical sympathectomy. Ptosis in both epinephrine- and 6-hydroxydopamine-treated rats was associated with a statistically significant depletion of ocular norepinephrine, as determined by a sensitive catecholamine radio enzyme assay. Ultrastructural evidence of nerve terminal degeneration was present near the smooth muscle of Müller within the eyelid of rats treated with epinephrine. This study provides further evidence epinephrine administration can result in chemical sympathectomy as has been described following 6-hydroxydopamine.