Autonomic drug effects after chronic lowering of ocular cholinergic input. II. Intraocular pressure responses.

Cholinergic input to the anterior segment of the eye was chronically reduced by ciliary ganglionectomy in cats and by treatment with hemicholinium-3 in both rabbits and cats. The parasympathetically denervated cat eyes developed super-sensitivity to the intraocular pressure lowering effects of carbachol and echothiophate. On the other hand, responsiveness to the similar effects of norepinephrine, epinephrine, and isoproterenol was not changed. After both acute and chronic treatment of rabbit eyes with hemicholinium-3, intraocular pressure was markedly lowered, but the facility of aqueous outflow after chronic treatment was not changed. During chronic treatment of cat eyes with hemicholinium-3, intraocular pressure was also lowered. Three days after chronic delivery of this acetylcholine synthesis inhibitor to the eyes of cats, the rate of formation of aqueous humor was reduced by 50 percent. These results suggest that chemical compounds lowering ocular cholinergic input may possess a pharmacological profile useful as an alternative means for the treatment of glaucoma.