title: Desensitization to topical epinephrine in the rabbit eye: attenuation by dexamethasone.
abstract: Desensitization of ocular adrenergic receptors was examined in vivo in albino rabbit eyes. Repeated topical administration of 2.0% l-epinephrine bitartrate (equivalent to 1.1% free base) to the rabbit eye resulted in the loss of ocular hypotensive response on the second day of daily or twice-daily treatment. Concurrent topical administration of dexamethasone phosphate (0.1%) prolonged the pressure-lowering effect of 2.0% l-epinephrine for up to 5 days. Loss of pressure-lowering response was accompanied by 100% inhibition of ciliary process beta-adrenergic-sensitive adenylate cyclase activity following 6 days of topical administration of l-epinephrine; inhibition of c-AMP synthesis was attenuated by dexamethasone (27% decrease in activity after 6 days of treatment). The data suggest that modulation of epinephrine-induced desensitization by corticosteroids in the rabbit eye is associated with stabilization of beta-adrenergic-sensitive adenylate cyclase activity.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000287:Administration, Topical; D000818:Animals; D002924:Ciliary Body / Q000201:enzymology; D003907:Dexamethasone / Q000494:pharmacology*; D004351:Drug Resistance; D004837:Epinephrine / Q000494:pharmacology*; D005123:Eye / Q000187:drug effects*; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D011817:Rabbits; D013268:Stimulation, Chemical
chemical_list: D003907:Dexamethasone; D000262:Adenylyl Cyclases; D004837:Epinephrine