Long-term administration of a substance P antagonist, (D-Pro2, D-Trp7,9)-SP, abolishes the response to ocular trauma.

The long-term effect of ocular administration of a substance P (SP) antagonist, (D-Pro2, D-Trp7,9)-SP, was studied in the rabbit. After 2-3 months of topical administration of the antagonist twice daily, a mild trauma was applied in the form of infrared irradiation of the iris. The control eye responded with disruption of the blood-aqueous barrier, the eye treated with the antagonist did not. Two days after termination of treatment, the response to ocular injury was still reduced. Another 2 days later, ocular injury evoked a normal response, which shows that the protection was reversible. No adverse reaction to the SP antagonist was noted.