Response of retinal vasculature to phenylephrine.

In a freshly enucleated bovine eye, the retinal arteries and veins constrict when phenylephrine is applied directly on the surface of the vessel walls. This "in situ" preparation allowed us to observe the reaction of retinal vessels without any surgical procedure that might alter the vascular response to agonists. These results indicate that alpha1-adrenergic receptors are present in the retinal vessels, which might therefore respond to vasoactive hormones. If, when, and how these reactions occur is still to be studied.