Hydroxyamphetamine increases intraocular pressure in rabbits

Abstract

Objective: To determine the effect of norepinephrine (NE) released from endogenous ocular stores on intraocular pressure (IOP) and aqueous flow in rabbits.

Methods: The IOP was measured with a pneumatonometer, the aqueous flow with a scanning fluorophotometer, and the aqueous NE by methylation with catechol-O-methyltransferase in the presence of S-adenosyl-L-[methyl-(3)H]methionine.

Results: Hydroxyamphetamine increased IOP in a dose-dependent fashion. Surgical removal of the superior cervical sympathetic ganglion eliminated the increase in IOP and pupil diameter; preganglionic section of the cervical sympathetic trunk did not. Hydroxyamphetamine increased the concentration of NE in the aqueous. Increased IOP was not accompanied by increased aqueous flow and was eliminated by blockade of alpha(1)-adrenergic receptors but not beta- or alpha(2)-adrenergic receptors.

Conclusions: Increased IOP after hydroxyamphetamine application is consistent with earlier suggestions that the nocturnal circadian increase in IOP in rabbits is mediated in part by NE released from ocular sympathetic nerves. However, failure of hydroxyamphetamine to increase aqueous flow and of beta-adrenergic blockade to blunt the increase in IOP does not support our suggestion that the nocturnal increase in IOP results in part from NE stimulation of ciliary process beta-adrenergic receptors and increased aqueous flow.

Clinical relevance: In addition to increasing pupil diameter, hydroxyamphetamine increases IOP.