TACHYKININS AS ENHANCERS OF PROSTAGLANDIN E-2-INDUCED INTRAOCULAR INFLAMMATION

The effects of tachykinins on prostaglandin E-2 (PGE(2))-induced intra ocular inflammation were investigated. PGE(2) (0.01% or 0.1%) instilla tion induced iridal hyperemia and protein leakage into the aqueous hum or in rabbits, but caused minimal miosis. Intravitreally injected subs tance P (SP) or neurokinin A (NKA), on the other hand, did not induce protein leakage into the aqueous humor in normal rabbits, but they (SP 10 mu g/eye or NKA 50 mu g/eye) did induce long-lasting miosis. The m iotic activity of SP was about five fold stronger than that of NKA. In travitreally injected SP (10 mu/eye) but not NKA (50 mu eye) markedly enhanced protein leakage into the aqueous humor induced by PGE(2) inst illation. Pretreatment with indomethacin partially blocked the enhanci ng effect of SP on protein leakage, while it did not block that of NKA . These results suggest that SP or NKA may enhance intraocular inflamm ation in vivo. However, the mechanisms of these effects of SP and NKA may be different. The enhancing effect of SP in eye inflammation may b e partially due to an increased turnover of arachidonic acid into PGE( 2) caused by activation of the enzyme cyclooxygenase.