Superior cervical ganglionectomy in monkeys: Aqueous humor dynamics and their responses to drugs

The role of sympathetic innervation in regulating the responses of aqueous humor flow, outflow facility and pupillary diameter to timolol and epinephrine was investigated in cynomolgus monkeys following unilateral superior cervical ganglionectomy. Aqueous humor flow was measured fluorophotometrically under pentobarbital anesthesia before the first and after the ninth of twice-daily topical doses of epinephrine, and under ketamine anesthesia before the first and after the ninth of twice-daily topical doses of timolol, 4-19 months after denervation. Baseline aqueous humor flow rates determined 2-4 months following denervation were 40% greater under ketamine than under pentobarbital anesthesia, with no difference between denervated and control eyes. Epinephrine increased aqueous humor flow by up to 50% in a dose-dependent fashion in both eyes, with a non-significant tendency toward slightly greater potency and efficacy in the denervated eyes. Timolol decreased aqueous humor flow by up to 50% in a dose-dependent fashion with equal maximal efficacy in both eyes, but with slightly and statistically significantly greater potency and efficacy in the control eyes at submaximal doses. Early (1-3 months) but not late (23-27 months) after denervation, baseline pupil diameter under ketamine anesthesia was smaller in the denervated eyes than in the controls. The mydriatic response to 600 μg epinephrine was more sensitive in the denervated than the control eye both early (1-3 months) and later on (23-27 months) after denervation; timolol had no effect on pupil diameter in either eye. No striking differences in intraocular pressure or refraction were observed between the eyes under any of these conditions. Resting outflow facility or resistance and perfusion-induced facility increase or resistance reduction, measured by two-level constant pressure perfusion under pentobarbital anesthesia 1·5-4·5 years after unilateral sympathectomy, did not differ significantly between sympathectomized and control eyes. Facility increased (by up to 30-50% beyond washout) and resistance decreased (by up to 20-30% beyond washout) similarly in control and sympathectomized eyes 10-60 min and 3-4 hr after bolus intracameral epinephrine doses of 0·55 and 5·5 μg.