Postjunctional adrenergic receptors in the rabbit eye: effects on uveal flow and intraocular pressure in isolated arterially perfused eyes.

In uveal vessels of isolated arterially perfused rabbit eyes there is direct evidence for the presence of post-junctional alpha 1-receptors and indirect evidence for alpha 2-receptors. Since vasoconstriction by epinephrine could not be blocked by an alpha 1-antagonist, only 30% by an alpha 2-antagonist and almost fully by the combination or by phentolamine, we suggest the presence of an intermediate alpha-type receptor which is neither alpha 1 nor alpha 2 but has characteristics of either. All alpha-types produce vasoconstriction and a fall in IOP. Of the beta-types only beta 1-receptors can be demonstrated. They mediate vasodilatation and a rise in IOP. Neither beta 2- nor non-selective beta-agonists or -antagonists (e.g. timolol) affect IOP or uveal flow.