Visual experience is one of the factors that influences the formation of orderly connections in the developing tectum of the frog, Xenopus laevis. Input from the ipsilateral eye is relayed to the tectum via the nucleus isthmi (NI), and this ipsilateral map normally is in register with the map which is relayed from the contralateral eye via the optic nerve. The matching-up of the two maps is dependent on visual input during development. Abnormal visual input, resulting from experimental rotation of one eye, can induce isthmotectal axons to terminate in different sites than normal. These processes take place during a critical period of late tadpole-early postmetamorphic life, and plasticity normally is lost thereafter. NMDA receptors play an important role in plasticity. Blocking those receptors during the critical period blocks plasticity, and a three-month application of NMDA after the critical period fully restores plasticity. The following experiments are designed to investigate further the role of NMDA receptors by answering the following questions. 1. What doses of NMDA are effective in re-establishing plasticity in adults, and do those doses alter tectal activity? 2. Must NMDA be present for a full three months to restore plasticity? 3. What is the morphology of isthmotectal axons in NMDA-treated tecta? 4. Does the number of NMDA receptors normally change during development? 5. Can NMDA induce plasticity de novo in Rana pipiens, a species which normally shows no reorganization after eye rotation? Dark-rearing prolongs the critical period and affords another tool for assessing mechanisms of plasticity. Axon branching patterns and NMDA receptor numbers in dark-reared Xenopus will be studied. A deeper understanding of how convergent binocular input affects topography requires identification of the tectal cells which receive those inputs. Combined anterograde filling of isthmotectal axons and immunocytochemical labeling of tectal cells will serve to identify targets of isthmotectal axons.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY003470-15
Application #
2158812
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1980-07-01
Project End
1996-06-30
Budget Start
1994-07-01
Budget End
1995-06-30
Support Year
15
Fiscal Year
1994
Total Cost
Indirect Cost
Name
State University of New York at Buffalo
Department
Physiology
Type
Schools of Dentistry
DUNS #
038633251
City
Buffalo
State
NY
Country
United States
Zip Code
14260
Udin, Susan B (2012) Binocular maps in Xenopus tectum: Visual experience and the development of isthmotectal topography. Dev Neurobiol 72:564-74
Udin, Susan B (2008) Isthmotectal axons maintain normal arbor size but fail to support normal branch numbers in dark-reared Xenopus laevis. J Comp Neurol 507:1559-70
Rybicka, Krystyna Kielan; Udin, Susan B (2005) Connections of contralaterally projecting isthmotectal axons and GABA-immunoreactive neurons in Xenopus tectum: an ultrastructural study. Vis Neurosci 22:305-15
Guo, Y; Udin, S B (2000) The development of abnormal axon trajectories after rotation of one eye in Xenopus. J Neurosci 20:4189-97
Bandarchi, J; Scherer, W J; Udin, S B (1994) Acceleration by NMDA treatment of visually induced map reorganization in juvenile Xenopus after larval eye rotation. J Neurobiol 25:451-60
Scherer, W J; Udin, S B (1994) Concanavalin A reduces habituation in the tectum of the frog. Brain Res 667:209-15
Rybicka, K K; Udin, S B (1994) Ultrastructure and GABA immunoreactivity in layers 8 and 9 of the optic tectum of Xenopus laevis. Eur J Neurosci 6:1567-82
Scherer, W J; Udin, S B (1992) Xenopus exhibits seasonal variation in retinotectal latency but not tecto-isthmo-tectal latency. J Comp Physiol A 171:207-12
Udin, S B; Fisher, M D; Norden, J J (1992) Isthmotectal axons make ectopic synapses in monocular regions of the tectum in developing Xenopus laevis frogs. J Comp Neurol 322:461-70
Udin, S B; Scherer, W J; Constantine-Paton, M (1992) Physiological effects of chronic and acute application of N-methyl-D-aspartate and 5-amino-phosphonovaleric acid to the optic tectum of Rana pipiens frogs. Neuroscience 49:739-47

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