EFFECT OF DIURETICS, CHANNEL MODULATORS AND SIGNAL INTERCEPTORS ON CONTRACTILITY OF THE TRABECULAR MESHWORK

Measurements of isometric tension were performed on isolated trabecula r meshwork (TM) and ciliary muscle (CM) strips of the bovine eye. Ante rior segments of bovine eyes with well-preserved TM were perfused to m easure outflow rate. (1) Bumetanide (10(-4) mol/l) and hydrochlorothia zide (10(-4) mol/l) did not change the contractility of TM and CM stri ps in the presence or absence of carbachol. Ethacrynic acid dose-depen dently relaxed TM and CM strips precontracted either by carbachol or e ndothelin. (2) Cytochalasin D totally relaxed TM and CM strips precont racted by carbachol. The outflow rate almost doubled after application of cytochalasin D. (3) The effects of various modulators of K+ and Ca 2+ channels are summarized. Carbachol and endothelin are postulated to modify nonselective cation channels. An effective blocker of nonselec tive cation channels (flufenamic acid) relaxed TM and CM precontracted by carbachol or endothelin. These relaxing effects were independent o f the relaxing effects of ethacrynic acid and isosorbide dinitrate. (4 ) Evidence for the presence of various transporters and receptors in T M cells is summarized. (5) The TM per se is a contractile element whic h is involved in the regulation of aqueous humor outflow The contracti lity of TM and CM cells is differently modulated.