Ocular inhibitory effects of the dopamine DA2 agonist (Ha-118) in cats and rabbits.
1. Topical administration of the dopamine (DA2) receptor agonist, Ha-118, produced unilateral ocular hypotension and miosis in normal cats. 2. The ocular hypotensive and mitotic effects of Ha-118 were not observed in surgically sympathectomized cats indicating that an intact sympathetic pathway is necessary to demonstrate activity. 3. Ha-118 caused dose-dependent suppression of contractions of the cat nictitating membrane (CNM) elicited by electrical stimulation of the pre- and postganglionic sympathetic nerve trunks but not by exogenously administered noradrenaline suggesting that Ha-118 affected prejunctional but not ganglionic or postjunctional receptors. 4. Sulpiride antagonized Ha-118-induced inhibition of neuronally mediated contractions in the CNM suggesting an interaction at DA2 receptors. 5. Topical administration of Ha-118 inhibited the rise in intraocular pressure induced by oral water loading in rabbits. 6. Topical pretreatment with metoclopramide, a DA2 antagonist, inhibited the ocular antihypertensive effect of Ha-118 in rabbits. 7. These studies demonstrate that Ha-118 decreased intraocular pressure (IOP) and pupil diameter (PD) in the cat and that this activity can be correlated with suppression of peripheral sympathetic tone in the CNM.
Potter
D E
DE
Center for Biotechnology, Baylor College of Medicine, Woodlands, Texas 77381.
Burke
J A
JA
Ogidigben
M J
MJ
D000818:Animals; D002415:Cats; D015259:Dopamine Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology; D015394:Molecular Structure; D009541:Nictitating Membrane / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects*; D011804:Quinolines / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011817:Rabbits; D014867:Water
D015259:Dopamine Agents; D011804:Quinolines; D014867:Water; C041540:Ha 118; D008787:Metoclopramide; D009638:Norepinephrine