Robert R. Trotter

Adrenergic and cholinergic drug effects of rabbit eyes after sympathetic denervation

Abstract The effects of adrenergic and cholinergic drugs on pupillary diameter and intraocular pressure of conscious rabbits were studied one week after surgical removal of the left superior cervical ganglion. In a first series of experiments, changes in pupil size were measured after topical application of each drug at progressively increasing doses to left eyes of control and experimental animals. After administration of either epinephrine, norepinephrine, or isoproterenol in this manner, denervated eyes showed an enhanced responsiveness, or supersensitivity, to the mydriatric actions of these durgs. After administration of either pilocarpine or carbachol, on the other hand, marked subsensitivity to the miotic effects of these cholinomimetics became evident. In a second series of experiments, changes in ocular tension were measured after drug application to both eyes of control and experimental animals. Doses of sympathomimetics exerting no significant effects on intraocular pressure in the control rabbits, i.e., 0.1% epinephrine, 1% norepinephrine, and 1% isoproterenol, caused a significant lowering of ocular tension in the denervated eyes. While doses of carbachol or echothiophate amounting to 3.2% and 0.25%, respectively, had no significant effect on ocular tension in eyes of control animals, these same doses increased intraocular pressure in the denervated eyes by 4–8 mm Hg. These results indicate that changes in responsiveness of the rabbit eye to cholinergic drugs accompany the development of supersensitivity to adrenergic amined after sympathetic denervation.

Effects of selective inhibition of type A and type B monoamine oxidase on intraocular pressure in the cat and the rabbit.

Ocular tension of conscious cats and rabbits was measured after topical application of clorgyline, a selective inhibitor of type A monoamine oxidase, or deprenyl, a selective inhibitor of line (1,4 and 12%) showed a dose-related reduction of intraocular pressure, with maximal lowerings amounting to 6 to 7 mm Hg. Pretreatment of eyes with clorgyline, 1%, markedly potentiated the pressure lowering response to epinephrine, 0.1%, applied topically. Sympathetic denervation almost completely abolished the effect of clorgyline. In contrast, deprenyl (2 to 8%) did not lower intraocular pressure after topical application to cat or rabbit eyes. beta-Phenylethylamine (2 to 16%) a specific substrate for the B form of monoamine oxidase, likewise did not lower ocular tension when given either alone or after pretreatment with deprenyl. These findings suggest that the intraocular pressure lowering effect of monoamine oxidase inhibitors is due primarily to inhibition of the A form of the enzyme and is dependent on intact sympathetic innervation.

REQUEST FOR OPHTHALMIC LITERATURE

To the Editor: —I am setting up the Division of Ophthalmology in a new fouryear medical school at West Virginia University Medical Center in Morgantown. In building an ophthalmic library from scratch, we are in need of those periodicals and books, in any language and of whatever age, found in any good ophthalmic library. It has occurred to me that heirs and executors may sometimes be uncertain as to the most appropriate means of putting to use the library of a deceased ophthalmologist. We welcome donations from such persons, or any person, such as an ophthalmologist who is retiring from practice. Acknowledgment of the source of acquisitions will be made by appropriate bookplates. The Division of Ophthalmology will pay freight charges. Persons interested in donating books and journals are invited to correspond with the undersigned. The Correspondence Section welcomes inquiries and comments of a general or specific nature. The Editors