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Abstract #6626 Published in IGR 4-1
Central imidazoline (I1) receptors modulate aqueous hydrodynamics
Ogidigben MJ; Potter DECurrent Eye Research 2001; 22: 358-366
The purpose of this work was to determine the relative contributions of central imidazoline (I1) receptors to the ocular hydrodynamic action of moxonidine. Moxonidine (MOX), an α2 and I1 receptor agonist, and efaroxan (EFA), a relatively selective I1 antagonist, were utilized to study alterations in intraocular pressure (IOP) and aqueous flow in New Zealand white rabbits subjected to intracerebroventricular (i.c.v.) cannulation and sympathectomy. I.c.v. administration of MOX (0.033, 0.33 and 3.33 μg) to normal rabbits produced dose-dependent, bilateral IOP decreases of 3, 6, and 8 mmHg, respectively. The ocular hypotensive response to MOX was immediate (ten minutes post-drug), lasted for one hour, and was inhibited by prior administration of efaroxan (3.33 μg i.c.v.). In unilaterally sympathectomized (SX) rabbits, the ocular hypotensive response induced by i.c.v. MOX in the denervated eye was attenuated approximately 50%, but the duration of ocular hypotension in the surgically altered eye was longer than that of the normal eye. MOX (0.33 μg i.c.v.) caused a statistically significant decrease (from 2.24 to 1.59 ml/min) in aqueous flow in normal eyes. In SX eyes, there was no change in aqueous flow by MOX, suggesting that IOP effect in i.c.v. MOX observed in the SX eye might be mediated by changes in outflow resistance. Sedation was observed in all the rabbits treated with MOX (i.c.v.) and was dose-dependent. These in vivo data support the suggestion that centrally located I1 receptors modulate the early contralateral response to topically administered MOX and are involved in lowering of IOP and aqueous flow in rabbit. In addition, expression of the full ocular hypotensive effect of centrally applied MOX depends on intact sympathetic innervation. Ocular hypotension induced by MOX in the SX eye may involve an effect on uveoscleral outflow.
Dr. D.E. Potter, Department of Pharmacology/Toxicology, Morehouse School of Medicine, Atlanta, GA 30310, USA
Classification:
2.6 Aqueous humor dynamics (Part of: 2 Anatomical structures in glaucoma)
