Uptake of [ 3H]noradrenaline by the ocular tissues of rabbit

Abstract

The uptake and storage of exogenous noradrenaline by adrenergic nerve terminals in the ocular tissues of rabbits were studied by autoradiography and fluorescence microscopy. Within 2 hr of intracameral injection of [3H]noradrenaline, uptake by iris, ciliary epithelium, episcleral and intrascleral vessels was complete. The exogenous noradrenaline stored up in the nerve terminals was slowly released over a period of 4–24 hr. The uptake by any tissue was dependent on the extent of adrenergic innervation. The uptake and storage of topically administered noradrenaline followed a similar pattern. Seventy-two hours after superior cervical ganglionectomy it was found that adrenergic nerve terminals had completely lost their uptake and storage capacity. It is suggested that the release of stored noradrenaline over a long period is responsible for the prolonged action on the outflow channels in rabbit eyes.