title: AII amacrine cells express the MT1 melatonin receptor in human and macaque retina.
abstract: AII amacrine cells are critical interneurons in the rod pathway of mammalian retina, active primarily in dim lighting conditions. Melatonin, a neuromodulator produced at night in the retina, is believed to induce retinal adaptation to dim lighting conditions in most vertebrate species examined to date, including humans. We hypothesized that melatonin may influence retinal light adaptation by acting on AII cells directly and thus investigated whether melatonin receptors were expressed in AII neurons. Postmortem nonpathological eyes from four human donors as well as two eyes from two Macaque Fasicularis monkeys were analyzed. Double immunocytochemistry was performed using an anti-MT(1) antibody and an antibody to calretinin, an AII marker. Analysis utilized confocal microscopy. A polyclonal anti-calretinin antibody labelled amacrine cells exhibiting the distinct AII morphology, in both human and macaque retina. MT(1) immunoreactivity in macaque retina was similar to human staining, in that horizontal, amacrine and ganglion cell bodies were stained, as were inner segments of photoreceptors. In human retina 86% of calretinin positive cells expressed the MT(1) receptor peripherally, whereas centrally, 78% colocalization was observed. In the macaque retina, 100% of AII amacrine cells expressed MT(1) immunoreactivity both centrally and peripherally. That virtually all AII neurons express the MT(1) receptor in both human and macaque retina, may provide the first evidence demonstrating a role for melatonin in AII regulation, furthering the hypothesis of melatonin function in retinal light adaptation.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Medical Sciences Building, 1 Kings College Circle, Rm 3321, Ont., M5S 1A8, Toronto, Canada. judite.scher@utoronto.ca
authors.forename: Judite
authors.initials: J
authors.lastname: Scher
authors.forename: Ellen
authors.initials: E
authors.lastname: Wankiewicz
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Brown
authors.forename: Hiroki
authors.initials: H
authors.lastname: Fujieda
mesh_terms: D025042:Amacrine Cells / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000032:analysis; D064032:Calbindin 2; D003623:Dark Adaptation / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008252:Macaca fascicularis; D018613:Microscopy, Confocal / Q000379:methods; D011956:Receptors, Cell Surface / Q000032:analysis*; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis*; D044094:Receptors, Melatonin; D012160:Retina / Q000276:immunology / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000276:immunology / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000276:immunology / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000276:immunology
chemical_list: D000906:Antibodies; C576764:CALB2 protein, human; D064032:Calbindin 2; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D064030:S100 Calcium Binding Protein G