Enzymology of the refractory media of the eye. X. Effects of topically administered bradykinin, amine releasers, and pargyline on aqueous humor dynamics.

The topical application of reseipine and the benzoquinolizine Ro 4-1284 to rabbit eyes leads to a significant depression of the intraocular pressure. This reduction is d,ue essentially to a depression of the formation rate and is counteracted by a small drop in facility of ouifiow. As in other biologic systems, the action of reserpine lasts longer and requires lower concentrations than that of the benzoquinolizine. Bradykinin, which is also capable of releasing amines, acts quite differently from these two agents by increasing the facility of outflow of the rabbit eye. Similarly, the rate of outflow in the excised bovine eye is enhanced markedly by this nonapeptide. The combined effects of the monoamine oxidase inhibitor (MAO) pargyline and the releasing agents depend a great deal on the sequence of drug application. When reserpine and pargyline are administered together for several days, extremely low values for the formation rate are observed. In most other combinations, the releasers cancel the action of the MAO inhibitor and vice versa. This indicates that, although the actions of reserpine or pargyline alone on the aqueous humor dynamics are quite similar, their mechanisms of action must be profoundly different. The phenomena cannot be interpreted alone in terms of changes of norepinephrine levels in the ciliary body.