This research proposal is an experimenal investigation into (1) the identification of synaptic transmitters, (2) the physiological basis of transmitter action at the single cell level, and (3) the morphological identification of physiologically and pharmacologically characterized cells. Inhibitory and excitatory transmitter agonists and antagonists are added to the bathing medium using perfused-retina eyecup preparations of rabbits and several types of amphibians (mudpuppy and tiger salamander). Analysis of drug action is based on intracellular electrode experiments using conventional recording techniques, single electrode voltage clamp techniques ad a lock-in amplifier for quantitative measurements of conductance changes. A similar, parallel set of experiments will be carried out using enzyme dissociated cells maintained in tissue culture conditions. Intracellular recording of single dissociated cells will be analyzed as agonists/antagonists are added to the bathing medium, iontophoretically applied, or introduced through pressure injection. The isolated retina of amphibians and rabbits will be studied for types and levels of amino acids released into the bathing medium, using reverse-phase high performance liquid chromatography. Particular emphasis will be placed on the identity of rod and cone transmitters. These experiments will also be combined with tissue culture techniques to fractionate the retina into limited neuronal populations, through the use of neuroactive ligands. The goal of this research is to identify synaptic transmitters and associate them with specific pathways and cell types. Several disease states which afflict the retina (retinitis pigmentosa; macular degeneration), show prolonged states in which photoreceptor function is compromised while leaving a more or less intact retina. An understanding of the chemicals involved in photoreceptor transmission, together with the synaptic receptors which mediate their action may help in the design of drug therapy to assist patients with limited vision.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
4R37EY003014-18
Application #
2158599
Study Section
Special Emphasis Panel (NSS)
Project Start
1978-09-30
Project End
1999-02-28
Budget Start
1994-03-01
Budget End
1995-02-28
Support Year
18
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Physiology
Type
Schools of Medicine
DUNS #
168559177
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Sullivan, Steve J; Miller, Robert F (2012) AMPA receptor-dependent, light-evoked D-serine release acts on retinal ganglion cell NMDA receptors. J Neurophysiol 108:1044-51
Sullivan, Steve J; Miller, Robert F (2010) AMPA receptor mediated D-serine release from retinal glial cells. J Neurochem 115:1681-9
Stevens, Eric R; Gustafson, Eric C; Sullivan, Steven J et al. (2010) Light-evoked NMDA receptor-mediated currents are reduced by blocking D-serine synthesis in the salamander retina. Neuroreport 21:239-44
Mitra, Pratip; Miller, Robert F (2007) Mechanism underlying rebound excitation in retinal ganglion cells. Vis Neurosci 24:709-31
Royer, Audrey S; Miller, Robert F (2007) Dendritic impulse collisions and shifting sites of action potential initiation contract and extend the receptive field of an amacrine cell. Vis Neurosci 24:619-34
Gustafson, Eric C; Stevens, Eric R; Wolosker, Herman et al. (2007) Endogenous D-serine contributes to NMDA-receptor-mediated light-evoked responses in the vertebrate retina. J Neurophysiol 98:122-30
Henderson, Dori; Miller, Robert F (2007) Low-voltage activated calcium currents in ganglion cells of the tiger salamander retina: experiment and simulation. Vis Neurosci 24:37-51
Mitra, Pratip; Miller, Robert F (2007) Normal and rebound impulse firing in retinal ganglion cells. Vis Neurosci 24:79-90
Miller, Robert F; Staff, Nathan P; Velte, Toby J (2006) Form and function of ON-OFF amacrine cells in the amphibian retina. J Neurophysiol 95:3171-90
O'Brien, Kylie B; Miller, Robert F; Bowser, Michael T (2005) D-Serine uptake by isolated retinas is consistent with ASCT-mediated transport. Neurosci Lett 385:58-63

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