title: Developmental pattern of NADPH-diaphorase positive neurons in chick optic tectum is sensitive to changes in visual stimulation.
abstract: The chick retinotectal system is a suitable model to investigate the mechanisms involved in the establishment of synaptic connections in whose refinement nitric oxide was implicated. The purpose of this work was to describe the developmental pattern of the nitric oxide synthase (NOS)-positive neurons as well as to determine if it is sensitive to changes in visual stimulation. The NADPH-diaphorase histochemical method was used to describe and quantify NOS neurons in normally stimulated and subnormally stimulated chickens. Nine types of NOS neurons were identified; seven of them express NOS until adulthood, while two of them show only a transient expression. The developmental pattern of NOS neurons follows the process of laminar segregation. It can be divided into three phases. The first includes the onset of NOS expression in periventricular neurons and the formation of a deep network of NOS fibers during early development. These neurons do not show any significant change in subnormally stimulated animals. The second phase includes the appearance of two transient NOS populations of bipolar neurons that occupy the intermediate layers during the optic fibers ingrowth. One of them significantly changes in subnormally stimulated chicks. The third phase occurs when the transitory expression of bipolar neurons decreases. It includes NOS expression in six neuronal populations that innervate the superficial retinorecipient layers. Most of these cells suffer plastic changes in subnormally stimulated chicks. The diversity of neuronal types with regard to their morphology, location, and sensitivity to visual stimulation strongly suggests that they serve different functions.
authors.affiliation: Institute of Cell Biology and Neurosciences "Prof. E. De Robertis," School of Medicine, University of Buenos Aires, 1121 Buenos Aires, Argentina. gscicolo@mail.retina.ar
authors.forename: Gabriel
authors.initials: G
authors.lastname: Scicolone
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Ortalli
authors.forename: Gabriela
authors.initials: G
authors.lastname: Alvarez
authors.forename: Juan José
authors.initials: JJ
authors.lastname: López-Costa
authors.forename: Melina
authors.initials: M
authors.lastname: Rapacioli
authors.forename: José Luis
authors.initials: JL
authors.lastname: Ferrán
authors.forename: Viviana
authors.initials: V
authors.lastname: Sanchez
authors.forename: Vladimir
authors.initials: V
authors.lastname: Flores
mesh_terms: D000818:Animals; D048430:Cell Shape; D002642:Chick Embryo / Q000033:anatomy & histology*; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010775:Photic Stimulation; D013477:Superior Colliculi / Q000033:anatomy & histology / Q000254:growth & development
chemical_list: D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase