Sympathectomy enhances the substance P-mediated breakdown of the blood-aqueous barrier in response to infrared irradiation of the rabbit iris.

Rabbits were subjected to infrared irradiation of the iris 1 month after unilateral cervical sympathectomy. The resulting breakdown of the blood-aqueous barrier was greatly enhanced on the sympathectomized side. In contrast, the response to intravitreally injected substance P (SP) was the same in both eyes. The enhancement of the response to IR irradiation could be abolished by pretreatment with an SP antagonist, (D-Pro2, D-Trp7,9)-SP.