Ocular responses evoked by capsaicin and prostaglandin E2 are inhibited by a substance P antagonist

Injection of capsaicin or prostaglandin E2 into the vitreous chamber of the rabbit eye resulted in miosis and breakdown of the blood-aqueous barrier, manifested in aqueous flare. Pretreatment with the neuronal blocker tetrodotoxin or the substance P antagonist (D-Pro, D-Trp)-SP greatly reduced the ocular responses to capsaicin and prostaglandin E2. The results suggest a role for neuronal substance P in the ocular response to injury.