[Adrenergic influence on the outflow facility and the ciliary muscle of enucleated bovine eyes].

In an effort to understand the aqueous outflow mechanism, the author compared changes in the outflow facility with the response of ciliary muscle, using fresh bovine eyes. Neither epinephrine nor isoproterenol alone increased the outflow facility, regardless of their concentrations. However, theophylline, caffeine, isobutylmethylxanthine (IBMX), and other phosphodiesterase (PDE) inhibitors, increased facility in a dose-dependent manner. Epinephrine alone neither relaxed the tone nor inhibited the nerve-mediated contraction of bovine ciliary muscle. Theophylline and IBMX relaxed the tone and inhibited the nerve-mediated contraction, whereas N-ethylmaleimide, iodoacetamide and iodoacetic acid also inhibited the nerve-mediated contraction, and elevated the tone of the ciliary muscle. All PDE inhibitors tested increased the outflow facility and inhibited the nerve-mediated contractions of the ciliary muscle, however, the effect of such drugs on the ciliary muscle tone varied. These results suggest that PDE inhibition may increase the conventional outflow of aqueous humor. PDE inhibitors has much greater influence on and around the outflow channels, from the viewpoint of change of outflow facility and ciliary muscle contraction.