Alapakkam P. Sampath
Assistant Professor
Department of Physiology & Biophysics
Zilkha Neurogenetic Institute
Keck School of Medicine
Research Topics
- Cellular Neurobiology
- Signal Transduction
- Vision Research
- Rod and Cone Phototransduction
- G-Protein Coupled Signaling Pathways
- Retinal Physiology and Signal Processing.
Research Overview
The Sampath laboratory is interested in understanding the molecular mechanisms underlying early visual processing to gain insight into the following questions. (1) How are G-protein-coupled signaling pathways in the retina controlled, and what are their functional properties? (2) How do these signaling pathways contribute to vision at low light levels? (3) How do alterations in retinal physiology influence visually guided behavior?To answer these questions we use electrophysiological and optical techniques to measure the light-evoked activity of neurons in the retina. We are interested in rod and cone phototransduction, in particular how these photoreceptors achieve such different response properties despite having similar G-protein signaling pathways. In addition, we are interested in how the second order retinal cells , the bipolar cells, interpret the rod and cone signals and ultimately how these signals are encoded at the retinal output, the ganglion cells. By following the light responses in each of these neurons we can gain insights into how light-evoked signals are procesed by the retina.
More recently we have begun to investigate correlations between retinal physiology and behavior for low light level vision (in collaboration with Jim Hurley, University of Washington). We use a water maze to characterize visual threshold in transgenic mice with altered retinal protein expression. Our goal is to correlate the physiological properties of the retina with changes in visually guided behavior. This work will provide insights into how the retina shapes signals that are functionally relevant for vision.
Contact Information
- Web Sites:
- Zilkha Neurogenetic Institute
PIBBS
Lab Website - E-mail:
- asampath@usc.edu
- Mailing Address:
- Zilkha Neurogenetic Institute
USC Keck School of Medicine
1501 San Pablo St., ZNI 435
Los Angeles, CA 90089 - Office Location:
- ZNI 435
- Office Phone:
- (323) 442-4413
- Fax:
- (323) 442-2448
Education
- University of California, Berkeley, B.A., 1994
- University of California, Los Angeles, Ph.D., 1999
- Stanford University, Postdoctoral Fellowship, 2001
- University of Washington, Postdoctoral Fellowship, 2004
Research Images
Selected Publications
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Okawa H, Sampath AP. (2007) Optimization of single-photon response transmission at the rod-to-rod bipolar synapse. Physiology (Bethesda). 22:279-86. -PubMed
Dunn FA, Doan T, Sampath AP, Rieke F. (2006) Controlling the gain of rod-mediated signals in the mammalian retina. J Neurosci. 26(15):3959-70. -PubMed
Sampath AP, Strissel KJ, Elias R, Arshavsky VY, McGinnis JF, Chen J, Kawamura S, Rieke F, Hurley JB. (2005) Recoverin improves rod-mediated vision by enhancing signal transmission in the mouse retina. Neuron. 46(3):413-20. -PubMed
Field GD, Sampath AP, Rieke F. (2005) Retinal processing near absolute threshold: from behavior to mechanism. Annu Rev Physiol. 67:491-514. -PubMed
Sampath AP, Rieke F. (2004) Selective transmission of single photon responses by saturation at the rod-to-rod bipolar synapse. Neuron. 41(3):431-43. -PubMed
Woodruff ML, Sampath AP, Matthews HR, Krasnoperova NV, Lem J, Fain GL. (2002) Measurement of cytoplasmic calcium concentration in the rods of wild-type and transducin knock-out mice. J Physiol. 542(Pt 3):843-54. -PubMed
Sampath AP, Baylor DA. (2002) Molecular mechanism of spontaneous pigment activation in retinal cones. Biophys J. 83(1):184-93. -PubMed