Abstract
On intraocular injection, l-epinephrine, l-norepinephrine, and l-isoproterenol produced an equal degree and duration of mydriasis in a molar dose of 1:2.75:5.5, respectively, in the unanesthetized rabbit. The injection of isotonic saline did not alter pupil size. No alteration of iris size was observed in the uninjected contralateral eye. This mydriatic action was unaltered by hexamethonium. The same potency ratio was observed in the anesthetized dog. Grossly, iris vascular constriction was observed with l-norepinephrine and iris vascular congestion with l-isoproterenol.
i-Epinephrine, d-epinephrine, and d-nor epinephrine produced an equal degree and duration of mydriasis in a molar dose of 1:5.0:5.5, respectively. Thus, d-epinephrine, d-norepinephrine, and l-isoproterenol were approximately equipotent. On the other hand, the d-isomer of isoproterenol was without effect in producing mydriasis even in an intraocular dose of 240 µg.
Systemically administered phenoxybenzamine prevented the mydriasis induced by intraocular d- or l-epinephrine, d-or i-nor epinephrine, and l-isoproterenol. Systemically administered dichioroisoproterenol did not prevent the mydriasis induced by intraocular l-isoproterenol.
The mydriatic action of intraocularly administered i-epinephrine or i-isoproterenol was enhanced 3 weeks after superior cervical ganglionectomy in dogs.
We conclude that the iris dilator contains only alpha adrenotropic receptors, but that l-isoproterenol is quite effective in activating such receptors in this organ. The iris vasculature appears to contain both alpha and beta adrenotropic receptors.
Footnotes
- Received April 30, 1961.
- © 1961, by The Williams & Wilkins Company
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