Chronic degeneration of aminergic nerve endings and blood-aqueous barrier.

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 alpha receptors, since the beta stimulant IP is inactive in both treated and untreated eyes.