Vascular Effects of Acetylcholinesterase Inhibitors in the Rabbit Eye: A Study with Fasciculin and Physostigmine

Abstract

The vascular effects of fasciculin and physostigmine, two acetylcholinesterase inhibitors, were studied with radioactively labelled microspheres in the rabbit eye. In addition, the effects on the intraocular pressure, pupil size and the aqueous humor protein concentration were determined. Both drugs were injected intracamerally in pentobarbital anesthetized and indomethacin pretreated animals. Fasciculin injected in a dose of 0.5 μg (0.7 × 10⁻¹⁰M) reduced blood flow in the anterior uvea as determined 30 and 60 min after injection. Higher doses had inconsistent effects. Physostigmine injected in a dose of 3 μg (1.1 × 10⁻⁸M) also reduced blood flow in the anterior uvea. The effect was most pronounced in the iris. Neither drug had any appreciable effect on choroidal or retinal blood flow. Both drugs caused pupillary constriction but the reduction in blood flow was not secondary to miosis. The effects on the intraocular pressure and aqueous humor protein concentration were inconsistent. The reduction in blood flow of the anterior uvea after intracameral injection of acetylcholinesterase inhibitors is consistent with a cholinergic vasoconstriction previously described in the eye during electrical stimulation of the oculomotor nerve.