Adrenergic effects on the isolated rabbit ciliary epithelium.

Norepinephrine, epinephrine, phenylephrine and isoproterenol have no effect on fluid secretion across the isolated rabbit ciliary epithelium, but all four drugs increase the hydraulic conductivity, or passive water permeability. By using a series of adrenergic antagonists (two α- and two β-compounds) it was possible to examine the type of receptor present in the ciliary epithelium which was responsible for the increased leakiness of the membrane. The results indicate that both α- and β-receptors exist in the ciliary epithelium and influence membrane permeability. From a consideration of the various influencing factors on intraocular pressure, the action of the drugs on lowering intraocular pressure is strongly suggested be on true outflow facility and pseudofacility.