Modulation of iris sphincter and ciliary muscles by urocortin 2.

摘要

Urocortin 2 (UCN2) is a peptide related to corticotropin-releasingfactor, capable of activating CRF-R2. Among its multisystemiceffects, it has actions in all 3 muscle subtypes. This study’s aimwas to determine its potential role in two of the intrinsic eyemuscle kinetics. Strips of iris sphincter (rabbit) and ciliary(bovine) muscles were dissected and mounted in isometric forcetransducersystems filled with aerated-solutions. Contraction waselicited using carbachol (10-6 M for iris sphincter, 10-5 M for ciliarymuscle), prior adding to all testing substances. UCN2 inducedrelaxation in iris sphincter muscle, being the effect maximal at10-7 M concentrations (-12.2 % variation vs. control). This effectwas abolished with incubation of indomethacin, antisauvagine-30,chelerytrine and SQ22536, but preserved with L-nitro-L-arginine.In carbachol pre-stimulated ciliary muscle, UCN2 (10-5 M)enhanced contraction (maximal effect of 18.2 % increase vs.control). UCN2 is a new modulator of iris sphincter relaxation,dependent of CRF-R2 activation, synthesis of prostaglandins(COX pathway) and both adenylate cyclase and PKC signalingpathways, but independent of nitric oxide production. Regardingciliary muscle, UCN2 enhances carbachol-induced contraction, inhigher doses.