The objective of the proposed research is to investigate light- dependent ionic channels in the plasma membrane of photoreceptors, and intracellular calcium changes that may contribute to the regulation of their activity. A large fraction of the experiments will make use of invertebrate photoreceptors, as they constitute an excellent model system for studying molecular aspects of visual excitation under physiological conditions. Experiments are designed to record both macroscopic and single channel currents in various classes of enzymatically isolated cells (ciliary and rhabdomeric), to characterize multiple light- dependent conductances. The effect of light adaptation, local stimulation and membrane voltage on single channel activity will be investigated, and direct action by cyclic GMP and calcium ions will be assessed on different channel types. In addition, the changes in intracellular calcium that occur in relation to visual excitation -- either directly or through specialized voltage- sensitive calcium channels -- will be monitored by means of recently developed optical techniques. The time course and spatial distribution of calcium changes under a variety of conditions will provide information on underlying mechanisms and their involvement in modulating the visual excitation process. Optical calcium measurements will be performed also on amphibian solitary photoreceptor cells.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY007559-07
Application #
2161568
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1988-03-01
Project End
1996-04-30
Budget Start
1994-05-01
Budget End
1995-04-30
Support Year
7
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Boston University
Department
Physiology
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02118
del Pilar Gomez, Maria; Nasi, Enrico (2005) A direct signaling role for phosphatidylinositol 4,5-bisphosphate (PIP2) in the visual excitation process of microvillar receptors. J Biol Chem 280:16784-9
del Pilar Gomez, Maria; Nasi, Enrico (2005) Calcium-independent, cGMP-mediated light adaptation in invertebrate ciliary photoreceptors. J Neurosci 25:2042-9
Gomez, Maria del Pilar; Nasi, Enrico (2005) On the gating mechanisms of the light-dependent conductance in Pecten hyperpolarizing photoreceptors: does light remove inactivation in voltage-dependent K channels? J Gen Physiol 125:455-64
Piccoli, Giuseppe; Del Pilar Gomez, Maria; Nasi, Enrico (2002) Role of protein kinase C in light adaptation of molluscan microvillar photoreceptors. J Physiol 543:481-94
Gomez, M P; Nasi, E (2000) Light transduction in invertebrate hyperpolarizing photoreceptors: possible involvement of a Go-regulated guanylate cyclase. J Neurosci 20:5254-63
Nasi, E; del Pilar Gomez, M (1999) Divalent cation interactions with light-dependent K channels. Kinetics of voltage-dependent block and requirement for an open pore. J Gen Physiol 114:653-72
Gomez, M P; Nasi, E (1997) Light adaptation in Pecten hyperpolarizing photoreceptors. Insensitivity to calcium manipulations. J Gen Physiol 109:371-84
Gomez, M P; Nasi, E (1997) Antagonists of the cGMP-gated conductance of vertebrate rods block the photocurrent in scallop ciliary photoreceptors. J Physiol 500 ( Pt 2):367-78
Gomez, M D; Nasi, E (1996) Ion permeation through light-activated channels in rhabdomeric photoreceptors. Role of divalent cations. J Gen Physiol 107:715-30
del Pilar Gomez, M; Nasi, E (1995) Activation of light-dependent K+ channels in ciliary invertebrate photoreceptors involves cGMP but not the IP3/Ca2+ cascade. Neuron 15:607-18

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