Autonomic regulation involved in the ocular hypotensive action of beta-adrenergic blocking agents

The effects of racemic propranolol and some related drugs on the intraocular pressure (IOP) were studied after topical application in rabbits. These drugs produced a significant reduction in IOP with the following order of potency: (-)-propranolol greater than timolol greater than (+/-)-propranolol greater than sotalol greater than (+)-propranolol greater than pranolium. Pretreatment of rabbit eyes with atropine significantly antagonized the ocular hypotensive action of (+/-)-propranolol, timolol and pranolium. Both (+/-)-propranolol and timolol produced a significant increase in pupil diameter in the presence of a submydriatic dose of atropine. The activities of monoamine oxidase and carbonic anhydrase were unaffected by (+/-)-propranolol, timolol and pranolium in-vitro. It is concluded from the results that both cholinergic and adrenergic mechanisms may be involved in the ocular hypotensive effects of the drugs.