Related Experiment Videos
Aqueous humor flow in sleeping humans is unaffected by norepinephrine infusion
B D Vanlandingham1, J S FitzSimon, R F Brubaker
1Department of Ophthalmology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Purpose:
Intravenous administration of the catecholamine epinephrine is known to have a stimulatory effect on aqueous humor flow in sleeping human subjects, an effect that is augmented by plasma corticosteroids. This study was performed to determine whether the closely related catecholamine norepinephrine has a similar effect on aqueous humor flow.
Methods:
Twenty normal subjects were studied. Aqueous flow was measured by fluorophotometry. At night during sleep, norepinephrine or placebo was infused intravenously (i.v.) between midnight and 6 AM. The rate of aqueous flow during the norepinephrine infusion was compared with the rate of flow during placebo infusion, with each subject serving as his/her own control. The urinary excretions of epinephrine and norepinephrine were measured at the end of each infusion period.
Results:
The norepinephrine infusion caused an 8% increase in systolic blood pressure (P < 0.001), a 15% increase in diastolic blood pressure (P < 0.001), and a 9% decrease in heart rate (P=0.003) compared with the placebo. The rate of aqueous humor flow during sleep from 12 AM to 6 AM was unchanged by norepinephrine. The rate was 1.27+/-0.31 microl/min (mean+/-SD) during i.v. infusion of placebo and 1.30+/-0.27 microl/min during infusion of norepinephrine (P=0.63).
Conclusions:
An infusion of norepinephrine during sleep that causes measurable changes in cardiovascular parameters has no measurable effects on the rate of aqueous humor flow. The lack of a measurable effect of a norepinephrine infusion contrasts to the stimulatory effect of an epinephrine infusion.