title: Presence of glutamate, glycine, and gamma-aminobutyric acid in the retina of the larval sea lamprey: comparative immunohistochemical study of classical neurotransmitters in larval and postmetamorphic retinas.
abstract: The neurochemistry of the retina of the larval and postmetamorphic sea lamprey was studied via immunocytochemistry using antibodies directed against the major candidate neurotransmitters [glutamate, glycine, gamma-aminobutyric acid (GABA), aspartate, dopamine, serotonin] and the neurotransmitter-synthesizing enzyme tyrosine hydroxylase. Immunoreactivity to rod opsin and calretinin was also used to distinguish some retinal cells. Two retinal regions are present in larvae: the central retina, with opsin-immunoreactive photoreceptors, and the lateral retina, which lacks photoreceptors and is mainly neuroblastic. We observed calretinin-immunostained ganglion cells in both retinal regions; immunolabeled bipolar cells were detected in the central retina only. Glutamate immunoreactivity was present in photoreceptors, ganglion cells, and bipolar cells. Faint to moderate glycine immunostaining was observed in photoreceptors and some cells of the ganglion cell/inner plexiform layer. No GABA-immunolabeled perikarya were observed. GABA-immunoreactive centrifugal fibers were present in the central and lateral retina. These centrifugal fibers contacted glutamate-immunostained ganglion cells. No aspartate, serotonin, dopamine, or TH immunoreactivity was observed in larvae, whereas these molecules, as well as GABA, glycine, and glutamate, were detected in neurons of the retina of recently transformed lamprey. Immunoreactivity to GABA was observed in outer horizontal cells, some bipolar cells, and numerous amacrine cells, whereas immunoreactivity to glycine was found in amacrine cells and interplexiform cells. Dopamine and serotonin immunoreactivity was found in scattered amacrine cells. Amacrine and horizontal cells did not express classical neurotransmitters (with the possible exception of glycine) during larval life, so transmitter-expressing cells of the larval retina appear to participate only in the vertical processing pathway.
authors.affiliation: Departamento de Biología Celular y Ecología, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain.
authors.forename: Verona
authors.initials: V
authors.lastname: Villar-Cerviño
authors.forename: Xesús M
authors.initials: XM
authors.lastname: Abalo
authors.forename: Begoña
authors.initials: B
authors.lastname: Villar-Cheda
authors.forename: Miguel
authors.initials: M
authors.lastname: Meléndez-Ferro
authors.forename: Emma
authors.initials: E
authors.lastname: Pérez-Costas
authors.forename: Gay R
authors.initials: GR
authors.lastname: Holstein
authors.forename: Giorgio P
authors.initials: GP
authors.lastname: Martinelli
authors.forename: María Celina
authors.initials: MC
authors.lastname: Rodicio
authors.forename: Ramón
authors.initials: R
authors.lastname: Anadón
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry; D064032:Calbindin 2; D018698:Glutamic Acid / Q000032:analysis*; D005998:Glycine / Q000032:analysis*; D007150:Immunohistochemistry; D007814:Larva / Q000033:anatomy & histology / Q000737:chemistry; D048428:Petromyzon / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D012160:Retina / Q000737:chemistry* / Q000166:cytology / Q000254:growth & development; D017299:Rod Opsins / Q000032:analysis; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D012680:Sensitivity and Specificity; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
chemical_list: D064032:Calbindin 2; D017299:Rod Opsins; D064030:S100 Calcium Binding Protein G; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005998:Glycine