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A. A. Rocha-Sousa, M. Tavares-Silva, S. Fonseca, S. Cardoso, S. Azevedo- Pinto, A. Leite-Moreira; Prostaglandins and NO Mediate the Urocortin2/ CRF2 Induced Relaxation of the Iris Sphincter Muscle. Invest. Ophthalmol. Vis. Sci. 2010;51(13):688.
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Urocortin 2 (Ucn2) is an endogenous peptide member of the CRF family that is expressed in the retinal pigmented epithelium and has a vasodilator effect in the retinal circulation. Our aim is to characterize the effect of Ucn2 in the iris sphincter muscle and its subcellular pathways.
The effect of increasing Ucn2 concentrations (10e-10-10e-6M) on carbacol-precontracted (10e-6M) rabbit iris sphincter muscles were tested alone and (n=9) in the presence of: (i)Nω-nitro-L-Arginine (L-NA;10e-5M;n=9), (ii)indomethacin (10e-5M;n=8) and (iii)antisauvagine-30 (10e-6M;n=8).
Ucn2 promoted a concentration-dependent decrease on active tension, maximal at 10-7M (18.6±6.1%). This effect was blunted with indomethacin (1.7±3.2%), L-NA (8.5±6.6%) and antisauvagine-30 (a CRF2 selective antagonist; .0±5.1%).
Ucn2 is a new neurohumoral factor that modulates the relaxation of the iris sphincter muscle. This effect is mediated by prostaglandins and is also dependent on nitric oxide production. CRF2 is the receptor involved in this relaxation.
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