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P3–181: The MT 2 melatonin receptor subtype is present in human retina and decreases in Alzheimer's disease
Author(s) -
Savaskan Egemen,
Jockers Ralf,
Eckert Anne,
Müller-Spahn Franz,
Meyer Peter
Publication year - 2006
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2006.05.1449
Subject(s) - melatonin , retina , outer plexiform layer , inner plexiform layer , melatonin receptor , pinealocyte , biology , ganglion cell layer , endocrinology , receptor , retinal , inner nuclear layer , medicine , pineal gland , microbiology and biotechnology , neuroscience , biochemistry
Background: Melatonin is an endogenous regulator of circadian and seasonal rhythms in vertebrates. A major production site of melatonin is the pineal gland, but it is also synthesized in the retina, the Harderian gland and the gastrointestinal tract. In the retina, locally produced melatonin acts as a paracrine signal of darkness by binding to specific receptors. In mammals, retinal melatonin does not contribute to circulating melatonin levels, but acts rather as a local neuromodulatory substance. Two different subtypes of G-protein coupled receptors, MT1 and MT2, transmit some of melatonin’s effects in mammals. Objective(s): We have previously shown the cellular localization of MT1 in the human retina to ganglion, amacrine and photoreceptor cells. We now present the first immunohistochemical evidence for the cellular distribution of MT2 in the human retina. Methods: MT2 was localized to human retina using immunohistochemistry. Conclusions: In elderly controls, MT2 was localized to ganglion and bipolar cells in the inner nuclear layer, and to the inner segments of the photoreceptor cells. In addition, cellular processes in inner and outer plexiform layers were strongly positive for MT2. Also, because we have previously found disease-related alterations in retinal MT1 expression during the course of Alzheimer’s disease (AD), eyes of AD patients were included to describe possible MT2 changes. In AD patients the overall intensity of MT2-staining was distinctly decreased in all cellular localizations. Since our previous results showed an increase in MT1 expression in AD retina, the two melatonin receptor subtypes may be differentially affected by the course of the neurodegenerative disorder.