Modification by timolol of catecholamine stimulation of chloride transport in isolated corneas.

In the isolated frog cornea, 10(-5)M timolol completely blocked the stimulation of chloride transport by 10(-6)M isoproterenol. In this preraration, timolol inconsistently modified the response to epinephrine. In some experiments, epinephrine added to the bathing medium after timolol caused a smaller than normal increase in chloride transport, but in other instances, epinephrine caused a decrease in chloride transport. In the isolated rabbit cornea, 10(-5)M timolol totally blocked the stimulation of chloride transport by 10(-6)M epinephrine. In vivo, topical treatment of rabbit eyes with 0.5% timolol resulted in corneas from these eyes having an inhibited response to epinephrine when incubated in vitro. This inability to stimulate chloride transport persisted for several days following termination of topical treatment with timolol.