The molecular mechanisms that transduce light energy into a change in membrane electrical potential in rod photoreceptors remain unknown. The project proposed here attempts to understand these mechanisms by investigating the role of Ca ions as intracellular messengers that couple the excitation of rhodopsin by light to the changes in membrane potential and the role of cyclic nucleotides as regulators of the messengers. The role of Ca is to be investigated in intact retinal rods through measurements of light-dependent changes in the concentration of this ion, both in the extracellular space, with ion-specific electrodes, and in the intracellular space, with fluorescent indicator dyes. The regulator role of cyclic nucleotides is to be investigated by studying the effects of intracellular cGMP, delivered via patch electrodes, on the light-dependent changes of Ca concentration. The function of rod outer segment discs in the control of Ca concentration changes will also be studied. A new technique will be developed that should permit the analysis of the Ca uptake and release functions of discs in very nearly intact rods under conditions that minimize loss of soluble components. The possible control of the Ca transport functions of rod discs by cyclic nucleotides will also be investigated.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY001586-12
Application #
3256035
Study Section
(SSS)
Project Start
1978-06-01
Project End
1990-05-31
Budget Start
1986-06-01
Budget End
1987-05-31
Support Year
12
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Ayoub, G S; Copenhagen, D R (1991) Application of a fluorometric method to measure glutamate release from single retinal photoreceptors. J Neurosci Methods 37:7-14
Korenbrot, J I; Miller, D L (1989) Cytoplasmic free calcium concentration in dark-adapted retinal rod outer segments. Vision Res 29:939-48
Ayoub, G S; Korenbrot, J I; Copenhagen, D R (1989) Release of endogenous glutamate from isolated cone photoreceptors of the lizard. Neurosci Res Suppl 10:S47-55
Korenbrot, J I; Perry, R; Copenhagen, D R (1987) Development and characterization of a polymer gel with an immobilized enzyme to measure L-glutamate. Anal Biochem 161:187-99
Hestrin, S; Korenbrot, J I (1987) Voltage-activated potassium channels in the plasma membrane of rod outer segments: a possible effect of enzymatic cell dissociation. J Neurosci 7:3072-80
Hestrin, S; Korenbrot, J I; Maricq, A V (1987) Kinetics of activation of acetylcholine receptors in a mouse muscle cell line under a range of acetylcholine concentrations. Biophys J 51:449-55
Miller, D L; Korenbrot, J I (1987) Kinetics of light-dependent Ca fluxes across the plasma membrane of rod outer segments. A dynamic model of the regulation of the cytoplasmic Ca concentration. J Gen Physiol 90:397-425
Korenbrot, J I; Miller, D L (1986) Calcium ions act as modulators of intracellular information flow in retinal rod phototransduction. Neurosci Res Suppl 4:S11-34
Ochs, D L; Korenbrot, J I; Williams, J A (1985) Relation between free cytosolic calcium and amylase release by pancreatic acini. Am J Physiol 249:G389-98