title: Functional activation of glutamate ionotropic receptors in the developing mouse retina.
abstract: Ionotropic glutamate receptors have been associated with early development of the visual process by regulating cell differentiation, cell motility, and synaptic contacts. We determined the expression of functional ionotropic glutamate receptors during development of the mouse retina by assessing 1-amino-4-guanidobutane (agmatine; AGB) immunolabelling after application of a range of glutamate analogs. Colocalization of AGB with calretinin and islet-1 allowed the identification of functional receptors in neurochemically defined neurons. Activation with kainate (KA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartate (NMDA) resulted in AGB entry into neurons consistent with that found previous receptor subunit localization studies in the developing retina. Temporal analysis revealed that application of 50 microM KA activated receptors as early as embryonic day 18 in the ventricular zone and in the ganglion cell layer, whereas 30 muM AMPA activated cells predominantly in the ganglion cell layer. Cholinergic amacrine cells showed functional KA and AMPA receptors upon their insertion into the conventional amacrine cell layer from postnatal day 1 (P1). OFF cone bipolar cells showed functional KA receptors from P6, at a developmental age when they are known to make contact with ganglion cells. NMDA activation led to diffuse AGB labeling at birth among cells in the ganglion cell layer, whereas, at P1, regularly spaced cholinergic amacrine cells in the conventional amacrine cell layer started to be responsive to NMDA. Non-NMDA receptors were first to show functional activation in the developing retina, and cholinergic amacrine cells displayed functional ionotropic glutamate receptors after reaching their final destination.
authors.affiliation: Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand.
authors.forename: Monica L
authors.initials: ML
authors.lastname: Acosta
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Chua
authors.forename: Michael
authors.initials: M
authors.lastname: Kalloniatis
mesh_terms: D000818:Animals; D064032:Calbindin 2; D018398:Homeodomain Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D060850:LIM-Homeodomain Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D018091:Receptors, AMPA / Q000378:metabolism*; D018092:Kainic Acid Receptors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D064032:Calbindin 2; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D064030:S100 Calcium Binding Protein G; D014157:Transcription Factors; C576511:Calb2 protein, mouse; C063843:insulin gene enhancer binding protein Isl-1