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      Effects of Some Opiates and Opioid Peptide Eyedrops on Ocular Melatonin Regulation in Rabbits

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          Levels of melatonin in rabbit eye tissues were detected by radioimmunoassay. Solutions of met-enkephalin, leu-enkephalin, α-endorphin and β-endorphin were given topically. Met-Enkephalin and α-endorphin lowered levels of melatonin in the iris, iris root-ciliary body, retina and choroid; leu-enkephalin raised levels in the retina and lowered them in other tissues. β-Endorphin only lowered levels in the iris root-ciliary body. DAGO (a μ agonist) given i.v. lowered levels of melatonin in the iris, iris root-ciliary body and retina. The δ and σ agonists given i.v. only lowered levels in the iris root-ciliary body, and a k agonist given i.v. raised levels in the ciliary body. No opiate binding sites could be detected in the rabbit iris or iris root-ciliay body for any class of receptor. Our data suggest opioids may be useful for treating glaucoma.

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          Author and article information

          Ophthalmic Res
          Ophthalmic Research
          S. Karger AG
          11 December 2009
          : 25
          : 6
          : 378-385
          Institute of Ocular Pharmacology and Department of Medical Pharmacology and Toxicology, TAMU College of Medicine, College Station, Tex., USA
          267340 Ophthalmic Res 1993;25:378–385
          © 1993 S. Karger AG, Basel

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          Pages: 8
          Original Paper


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