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Endogenous opioids regulate cell proliferation in the retina of developing rat
T Isayama1, P J McLaughlin, I S Zagon
1Department of Anatomy, Pennsylvania State University, M.S. Hershey Medical Center, Hershey 17033.
Brain Research
|March 22, 1991
Summary
Endogenous opioids and opioid receptors regulate cell proliferation in the developing retina. These natural inhibitory factors are present in developing but not adult retinal cells.
Area of Science:
- Neuroscience
- Developmental Biology
- Ophthalmology
Background:
- Endogenous opioid systems modulate various physiological processes.
- Their role in retinal development is not well understood.
Purpose of the Study:
- To investigate the role of endogenous opioids and opioid receptors in modulating cell proliferation in the developing mammalian retina.
Main Methods:
- Administered [Met5]-enkephalin and naloxone to 1-day-old rats.
- Utilized [3H]thymidine incorporation to assess cell proliferation.
- Performed immunocytochemistry and in vitro autoradiography to detect enkephalin and binding sites.
Main Results:
- [Met5]-enkephalin significantly reduced cell proliferation, an effect blocked by naloxone.
- Naltrexone increased cell proliferation, indicating opioid receptor involvement.
- Enkephalin-like immunoreactivity and binding sites were found in developing, but not adult, retina.
Conclusions:
- Endogenous opioids and opioid receptors are present in the developing mammalian retina.
- Endogenous opioids act as inhibitory trophic factors regulating retinal cell proliferation.
- These systems are specific to the developing retina, disappearing in adulthood.