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Hydroxyamphetamine increases intraocular pressure in rabbits.
1Department of Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208061, New Haven, CT 06520-8061. douglas.gregory@yale.edu
Archives of Ophthalmology (Chicago, Ill. : 1960)
|February 15, 2001
Summary
Hydroxyamphetamine increases intraocular pressure (IOP) in rabbits by releasing norepinephrine from ocular stores, mediated by alpha(1)-adrenergic receptors. This effect on IOP does not involve increased aqueous flow.
Area of Science:
- Ophthalmology
- Neuroscience
- Pharmacology
Background:
- Norepinephrine (NE) is present in ocular tissues and may influence intraocular pressure (IOP).
- The role of endogenous ocular NE in regulating IOP and aqueous humor dynamics requires further elucidation.
Purpose of the Study:
- To investigate the effect of endogenously released norepinephrine on intraocular pressure (IOP) and aqueous humor flow in rabbits.
- To determine the adrenergic receptor subtypes involved in hydroxyamphetamine-induced IOP changes.
Main Methods:
- Intraocular pressure (IOP) measured using a pneumatonometer.
- Aqueous humor flow assessed via scanning fluorophotometry.
- Aqueous humor norepinephrine (NE) quantified using catechol-O-methyltransferase methylation assay.
Main Results:
- Hydroxyamphetamine administration led to a dose-dependent increase in IOP and aqueous humor NE concentration.
- Surgical removal of the superior cervical sympathetic ganglion abolished the IOP increase.
- The IOP elevation was mediated by alpha(1)-adrenergic receptors and was not associated with changes in aqueous humor flow.
Conclusions:
- Norepinephrine release from ocular sympathetic nerves contributes to IOP elevation.
- The mechanism involves alpha(1)-adrenergic receptor activation, independent of changes in aqueous humor flow.
- Findings do not support a role for beta-adrenergic receptors in mediating nocturnal IOP increases via enhanced aqueous flow.