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.