Ocular hypotensive action of ergoline derivatives in rabbits: effects of sympathectomy and domperidone pretreatment

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Abstract
Ergot derivatives, such as bromocriptine, lergotrile and pergolide, are potent dopaminergic agonists in various biological systems. In topical doses ranging from 0.001 to IZ applied unilaterally, each agent produced dose-related ocular hypotension in normal rabbits. Utilizing an intraocular pressure (IOP) recovery rate method (aqueous formation index), each agent was observed to suppress the recovery rate of IOP in normal rabbits. Pretreatment with a prejunctional dopamine receptor antagonist (domperidone) inhibited the ocular hypotensive effect of bromocriptine and pergolide more than that of lergotrile. In rabbits with unilateral superior cervical ganglionectomies, IOP was lowered appreciably less by these compounds in the denervated eyes. These studies indicate that: a) lowering of IOP by these ergot derivatives is dependent, in part, on suppression of sympathetic neuronal activity; b) the most probable sites of action are DA2 receptors on sympathetic nerve endings or in sympathetic ganglia; c) ocular hypotension is produced, in part, by suppressing aqueous humor formation.