Potential role of imidazoline (I1) receptors in modulating aqueous humor dynamics.

1. Moxonidine (MOX), injected icvt into the anterior lateral ventricle of NZW rabbits, induced bilateral, ocular hypotension (> 7.0 mmHg) that persisted for two hrs. 2) Oxymetazoline (OXY), injected icvt into the anterior lateral ventricle of NZW rabbits, induced bilateral ocular hypotension (> 7.0 mmHg) that peaked at two hrs. 3) Unilateral topical application of OXY induced maximal, bilateral ocular hypotension (> 12 mmHg), at 3 hrs, in both the contralateral and ipsilateral eyes, that persisted more than 12 hrs. 4) The putative imidazoline (I1) antagonist, efaroxan, injected icvt into the anterior lateral ventricle, inhibited significantly the ocular hypotension produced by icvt MOX, icvt OXY, and unilateral topical OXY. 5) Imidazoline (I1) receptors, located in the CNS, play a role in MOX- and OXY-induced ocular hypotension, as suggested by the ability of the putative imidazoline (I1) receptor antagonist efaroxan, to inhibit icvt MOX-, icvt OXY- and topical OXY-induced ocular hypotension.