The overall objective of our research is to understand the detailed cellular and synaptic mechanisms underlying center and surround responses of retinal bipolar cells (BCs). Specifically, we will look at how neurons that mediate BC center and surround inputs in the outer retina (photoreceptors and horizontal cells (HCs)) interact with one another, and how adaptation, neuromodulators and the circadian clock regulate these cell-cell interactions and, consequently, BC receptive fields. We plan to use dual voltage clamp techniques to study cell-cell interactions at the photoreceptor, BC and HC levels, and use microelectrode voltage recording techniques to study receptive field properties of various types of cones, BCs and HCs. These two complementary approaches, along with the new knowledge and technical advances developed during the past years, will be applied to the salamander retina model system to study mechanisms underlying photoreceptor, HC and BC coupling and HC feedback/feedforward synaptic inputs to cones and BCs. These are common features of synaptic organization found in most vertebrate retinas. However, experiments involved in studying these features are technically difficult, if not impossible, to be carried out in many other vertebrates, including the mouse (thus issues to be addressed here complement, but do not overlap with our mouse grant). In this competing renewal application, we plan to continue our studies by focusing on 4 specific aims: (1) properties and modulation of electrical synapses between various pairs of photoreceptors (2 types of rods and 4 types of cones), (2) mechanisms underlying the sign-inverting, rod->cone transient signaling pathways in cones;(3) mechanisms underlying the depolarizing surround (feedback from HCs) responses in various types of cones; and (4) properties and modulation of HC and BC coupling and roles of cell-cell interaction in shaping BC and HC receptive fields. Results obtained will provide a detailed description of cell-cell interactions between neurons in the outer retina that are responsible for mediating the center and surround synaptic inputs in various types of BCs. Because of the similarities in outer retinal synaptic organizations between salamander and other vertebrates, knowledge obtained from this project will facilitate our understanding of how electrical/chemical synapses and BC receptive fields in mammalian and human retinas are organized, and provide important clues for developing animal models for various retinal diseases.

Public Health Relevance

Understanding how electrical and chemical synapses mediating receptive field organization in the outer retina is a fundamental and essential step for unraveling mechanisms of visual perception and brain operation. Results obtained from this project will provide crucial information on how specific defects in photoreceptor, bipolar cell and horizontal cell synapses are responsible for the onset of eye diseases, such as retinitis pigmentosa, macular degeneration, and congenital stationary night blindness.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY004446-31
Application #
8317672
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Greenwell, Thomas
Project Start
1982-02-01
Project End
2015-09-29
Budget Start
2012-09-30
Budget End
2013-09-29
Support Year
31
Fiscal Year
2012
Total Cost
$375,600
Indirect Cost
$135,600
Name
Baylor College of Medicine
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
Cowan, Cameron S; Abd-El-Barr, Muhammad; van der Heijden, Meike et al. (2016) Connexin 36 and rod bipolar cell independent rod pathways drive retinal ganglion cells and optokinetic reflexes. Vision Res 119:99-109
He, Feng; Agosto, Melina A; Anastassov, Ivan A et al. (2016) Phosphatidylinositol-3-phosphate is light-regulated and essential for survival in retinal rods. Sci Rep 6:26978
Wang, Jing; Jacoby, Roy; Wu, Samuel M (2016) Physiological and morphological characterization of ganglion cells in the salamander retina. Vision Res 119:60-72
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Tse, Dennis Y; Lotfi, Parisa; Simons, David L et al. (2015) Electrophysiological and Histological Characterization of Rod-Cone Retinal Degeneration and Microglia Activation in a Mouse Model of Mucopolysaccharidosis Type IIIB. Sci Rep 5:17143
Kim, Jin Young; Song, Ji Yun; Karnam, Santi et al. (2015) Common and distinctive localization patterns of Crumbs polarity complex proteins in the mammalian eye. Gene Expr Patterns 17:31-7
Tse, Dennis Y; Chung, Inyoung; Wu, Samuel M (2014) Possible roles of glutamate transporter EAAT5 in mouse cone depolarizing bipolar cell light responses. Vision Res 103:63-74

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