The vertebrate retina is an extension of the central nervous system that controls visual signaling and circadian rhythm. Our laboratory is interested in how the retina adapts to changing light intensities in the natural environment. We are presently studying the regulation of 2 G protein-coupled receptor kinases, GRK1 and GRK7, that participate in signal termination in the light-detecting cells of the retina, the rods and cones. Signal termination helps these cells recover from light exposure and adapt to continually changing light intensities. Recently, we determined that GRK1 and GRK7 are phosphorylated by cAMP-dependent protein kinase (PKA). Since cAMP levels are regulated by light in the retina, phosphorylation by PKA may be important in recovery and adaptation. Biochemical and molecular approaches are used in 2 model organisms, mouse and zebrafish, to address the role of PKA in retina function. Keywords: cAMP, cone, G protein-coupled receptor, GPCR, GRK, kinase, neurobiology, opsin, PKA, retina, rhodopsin rod, second messenger, signal transduction, vision.