Chronic degeneration of aminergic nerve endings and blood-aqueous barrier

Summary

Chemical sympathectomy of the anterior segment of the eye was performed in rabbits with 6-hydroxydopamine (6-OHDA) intravitreously injected. The response of the pupillary diameter (PD) and intraocular pressure (IOP) to NE, E and Isoproterenol was determined through instillation of the drugs in the pretreated and control eyes. The results were as follows:

• 1) Both PD and IOP at different intervals of time from the injection show a sharp decrease in the treated eye.

• 2) About four weeks after the injection, the instillation of NE and E increases the PD only in the 6-OHDA pretreated eyes, while IP administration is not effective on both control and pretreated eyes.

• 3) The instillation of the three drugs, while decreasing IOP in the control eyes, does not modify the already low IOP in the pretreated eyes.

The authors suggest the presence of a postdenervation supersensitivity affecting only the α receptors, since the β stimulant IP is inactive in both treated and untreated eyes.