Melatonin Receptor Blockers Enhance Photoreceptor Survival and Function in Light Damaged Rat Retina

  • Ronald A. Bush
  • Takeshi Sugawara
  • P. Michael Iuvone
  • Paul A. Sieving


Melatonin is an important retinal neurohormone involved in rhythmic photoreceptor metabolism and in regulating the release of retinal dopamine. Systemic administration of melatonin and conditions supporting its synthesis in the retina seem to be related to increased light damage susceptibility. We found that intraocular injection of competitive melatonin receptor antagonists prior to the dark period before bright light exposure resulted in substantial protection of photoreceptors from light damage. Photoreceptor cell structure was much better preserved in antagonist injected eyes and the ERG threshold was approximately 2 log units of intensity lower. Intraocular injection of a number of other compounds which are known to affect endogenous dopamine levels or stimulate or block dopamine receptors did not have a significant effect on the ERG. However, some showed a tendency to reduce or enhance the effect of light damage on the ERG depending on their expected effect on dopamine levels. These results indicate that blocking the action of endogenous melatonin at retinal receptors can protect photoreceptors from damage by light. Further work is needed to investigate a possible role for dopamine in this protection.


Dopamine Release Retinal Degeneration Light Damage Flash Intensity Endogenous Melatonin 
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Copyright information

© Kluwer Academic / Plenum Publishers 1999

Authors and Affiliations

  • Ronald A. Bush
    • 1
  • Takeshi Sugawara
    • 1
  • P. Michael Iuvone
    • 2
  • Paul A. Sieving
    • 1
  1. 1.Department of OphthalmologyCenter for Retinal and Macular Degeneration University of MichiganAnn Arbor
  2. 2.Department of PharmacologyEmory University School of MedicineAtlanta

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