Alapakkam P Sampath

Title(s)Professor, Ophthalmology
SchoolMedicine
ORCID ORCID Icon0000-0002-0785-9577 Additional info
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    Other Positions
    Title(s)Professor, Neurobiology


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    Collapse Education and Training
    University of California, BerkeleyAB05/1994Molecular and Cell Biology
    University of California, Los AngelesPhD05/1999Physiological Science
    Stanford UniversityPostdoc12/2001Neurobiology
    University of WashingtonSr Fellow12/2004Physiology & Biophysics

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    Collapse Overview
    My research interests have centered on the physiological function of retinal photoreceptor cells, the rods and cones. In particular, I have studied mechanisms of phototransduction activation and regulation, and how the photoreceptor cell output is represented in the retinal circuitry. Since 2005, the major research focus of my independent laboratory has been in using transgenic mice that display perturbations in photoreceptor function, or retinal connectivity, to establish how rod and cone photoreceptors relay light-evoked signals to bipolar cells over a wide range of light intensities. Much of this work has focused on how single-photon responses are transmitted across the retinal circuitry under conditions where few of the rods are generating them. However, more recently the laboratory has endeavored to establish the mechanisms by which both rod and cone photoreceptors function over a wide range of light intensities, and how retinal function is compromised following retinal degeneration.

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    Collapse Research Activities and Funding
    Molecular Mechanisms of Photoreceptor Adaptation
    NIH R01EY029817Feb 1, 2019 - Jan 31, 2024
    Role: Principal Investigator
    Molecular Basis of Photoreceptor Wiring
    NIH R01EY028033May 1, 2017 - Apr 30, 2022
    Role: Co-Principal Investigator
    Analyses of retinal circuits after rod rescue in a mouse model of human blindness
    NIH R01EY027193Sep 1, 2016 - Aug 31, 2021
    Role: Co-Principal Investigator
    Functional characteristics of rod pathways in the retina
    NIH R01EY017606Aug 1, 2006 - Jul 31, 2017
    Role: Principal Investigator
    Signal Transduction in Retinal On-Bipolar Cells
    NIH F32EY014784Mar 16, 2003 - Mar 15, 2005
    Role: Principal Investigator
    Vision Science Training Program
    NIH T32EY007026Jul 1, 1975 - Aug 31, 2022
    Role: Principal Investigator

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    Collapse Publications
    Publications listed below are automatically derived from MEDLINE/PubMed and other sources, which might result in incorrect or missing publications. Researchers can login to make corrections and additions, or contact us for help. to make corrections and additions.
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    1. A hyperpolarizing rod bipolar cell in the sea lamprey, Petromyzon marinus. J Exp Biol. 2022 04 15; 225(8). Frederiksen R, Fain GL, Sampath AP. PMID: 35319772.
      View in: PubMed   Mentions:    Fields:    Translation:AnimalsCells
    2. Reproducibility of the Rod Photoreceptor Response Depends Critically on the Concentration of the Phosphodiesterase Effector Enzyme. J Neurosci. 2022 03 16; 42(11):2180-2189. Morshedian A, Sendek G, Ng SY, Boyd K, Radu RA, Liu M, Artemyev NO, Sampath AP, Fain GL. PMID: 35091503; PMCID: PMC8936574.
      View in: PubMed   Mentions:    Fields:    Translation:AnimalsCells
    3. Light responses of mammalian cones. Pflugers Arch. 2021 09; 473(9):1555-1568. Fain GL, Sampath AP. PMID: 33742309; PMCID: PMC9413617.
      View in: PubMed   Mentions: 4     Fields:    Translation:HumansAnimalsCells
    4. Rod Photoreceptors Avoid Saturation in Bright Light by the Movement of the G Protein Transducin. J Neurosci. 2021 04 14; 41(15):3320-3330. Frederiksen R, Morshedian A, Tripathy SA, Xu T, Travis GH, Fain GL, Sampath AP. PMID: 33593858; PMCID: PMC8051685.
      View in: PubMed   Mentions: 2     Fields:    Translation:AnimalsCells
    5. Pupillary light reflex of lamprey Petromyzon marinus. Curr Biol. 2021 01 25; 31(2):R65-R66. Morshedian A, Huynh TH, Frederiksen R, Fain GL, Sampath AP. PMID: 33497630; PMCID: PMC9406759.
      View in: PubMed   Mentions: 1     Fields:    Translation:AnimalsCells
    6. Elevated energy requirement of cone photoreceptors. Proc Natl Acad Sci U S A. 2020 08 11; 117(32):19599-19603. Ingram NT, Fain GL, Sampath AP. PMID: 32719136; PMCID: PMC7431031.
      View in: PubMed   Mentions: 20     Fields:    Translation:HumansAnimalsCells
    7. Energy Shortage in Human and Mouse Models of SLC4A11-Associated Corneal Endothelial Dystrophies. Invest Ophthalmol Vis Sci. 2020 07 01; 61(8):39. Zhang W, Frausto R, Chung DD, Griffis CG, Kao L, Chen A, Azimov R, Sampath AP, Kurtz I, Aldave AJ. PMID: 32721020; PMCID: PMC7425690.
      View in: PubMed   Mentions: 5     Fields:    Translation:HumansAnimalsCells
    8. Separate ON and OFF pathways in vertebrate vision first arose during the Cambrian. Curr Biol. 2020 06 08; 30(11):R633-R634. Ellis EM, Frederiksen R, Morshedian A, Fain GL, Sampath AP. PMID: 32516608; PMCID: PMC9413601.
      View in: PubMed   Mentions: 2     Fields:    Translation:AnimalsCells
    9. Diminished Cone Sensitivity in cpfl3 Mice Is Caused by Defective Transducin Signaling. Invest Ophthalmol Vis Sci. 2020 04 09; 61(4):26. Chen NS, Ingram NT, Frederiksen R, Sampath AP, Chen J, Fain GL. PMID: 32315379; PMCID: PMC7401474.
      View in: PubMed   Mentions:    Fields:    Translation:AnimalsCells
    10. LRR-ning the Rules: Synapse Organization in the Primary Rod Pathway. Neuron. 2020 03 18; 105(6):949-951. Peng YR, Sampath AP. PMID: 32191854.
      View in: PubMed   Mentions:    Fields:    Translation:AnimalsCells
    11. Membrane conductances of mouse cone photoreceptors. J Gen Physiol. 2020 03 02; 152(3). Ingram NT, Sampath AP, Fain GL. PMID: 31986199; PMCID: PMC7054858.
      View in: PubMed   Mentions: 8     Fields:    Translation:AnimalsCells
    12. Voltage-clamp recordings of light responses from wild-type and mutant mouse cone photoreceptors. J Gen Physiol. 2019 11 04; 151(11):1287-1299. Ingram NT, Sampath AP, Fain GL. PMID: 31562185; PMCID: PMC6829558.
      View in: PubMed   Mentions: 15     Fields:    Translation:AnimalsCells
    13. Activation of Rod Input in a Model of Retinal Degeneration Reverses Retinal Remodeling and Induces Formation of Functional Synapses and Recovery of Visual Signaling in the Adult Retina. J Neurosci. 2019 08 21; 39(34):6798-6810. Wang T, Pahlberg J, Cafaro J, Frederiksen R, Cooper AJ, Sampath AP, Field GD, Chen J. PMID: 31285302; PMCID: PMC6703885.
      View in: PubMed   Mentions: 12     Fields:    Translation:HumansAnimalsCells
    14. Light-Driven Regeneration of Cone Visual Pigments through a Mechanism Involving RGR Opsin in Müller Glial Cells. Neuron. 2019 06 19; 102(6):1172-1183.e5. Morshedian A, Kaylor JJ, Ng SY, Tsan A, Frederiksen R, Xu T, Yuan L, Sampath AP, Radu RA, Fain GL, Travis GH. PMID: 31056353; PMCID: PMC6586478.
      View in: PubMed   Mentions: 38     Fields:    Translation:AnimalsCells
    15. Rod and cone interactions in the retina. F1000Res. 2018; 7. Fain G, Sampath AP. PMID: 29899971; PMCID: PMC5968360.
      View in: PubMed   Mentions: 12     Fields:    
    16. LRIT1 Modulates Adaptive Changes in Synaptic Communication of Cone Photoreceptors. Cell Rep. 2018 03 27; 22(13):3562-3573. Sarria I, Cao Y, Wang Y, Ingram NT, Orlandi C, Kamasawa N, Kolesnikov AV, Pahlberg J, Kefalov VJ, Sampath AP, Martemyanov KA. PMID: 29590623; PMCID: PMC5902029.
      View in: PubMed   Mentions: 9     Fields:    Translation:HumansAnimalsCells
    17. The Transduction Cascade in Retinal ON-Bipolar Cells: Signal Processing and Disease. Annu Rev Vis Sci. 2017 09 15; 3:25-51. Martemyanov KA, Sampath AP. PMID: 28715957; PMCID: PMC5778350.
      View in: PubMed   Mentions: 29     Fields:    Translation:HumansAnimalsCells
    18. Behavioural and physiological limits to vision in mammals. Philos Trans R Soc Lond B Biol Sci. 2017 Apr 05; 372(1717). Field GD, Sampath AP. PMID: 28193817; PMCID: PMC5312022.
      View in: PubMed   Mentions: 12     Fields:    Translation:AnimalsCells
    19. Voltage-sensitive conductances increase the sensitivity of rod photoresponses following pigment bleaching. J Physiol. 2017 06 01; 595(11):3459-3469. Pahlberg J, Frederiksen R, Pollock GE, Miyagishima KJ, Sampath AP, Cornwall MC. PMID: 28168711; PMCID: PMC5451700.
      View in: PubMed   Mentions: 14     Fields:    Translation:AnimalsCells
    20. The Auxiliary Calcium Channel Subunit α2δ4 Is Required for Axonal Elaboration, Synaptic Transmission, and Wiring of Rod Photoreceptors. Neuron. 2017 Mar 22; 93(6):1359-1374.e6. Wang Y, Fehlhaber KE, Sarria I, Cao Y, Ingram NT, Guerrero-Given D, Throesch B, Baldwin K, Kamasawa N, Ohtsuka T, Sampath AP, Martemyanov KA. PMID: 28262416; PMCID: PMC5364038.
      View in: PubMed   Mentions: 47     Fields:    Translation:HumansAnimalsCells
    21. Why are rods more sensitive than cones? J Physiol. 2016 10 01; 594(19):5415-26. Ingram NT, Sampath AP, Fain GL. PMID: 27218707; PMCID: PMC5043029.
      View in: PubMed   Mentions: 44     Fields:    Translation:AnimalsCells
    22. Changes in ganglion cell physiology during retinal degeneration influence excitability by prosthetic electrodes. J Neural Eng. 2016 Apr; 13(2):025001. Cho A, Ratliff C, Sampath A, Weiland J. PMID: 26905177; PMCID: PMC4852154.
      View in: PubMed   Mentions: 12     Fields:    Translation:AnimalsCells
    23. Mechanism for Selective Synaptic Wiring of Rod Photoreceptors into the Retinal Circuitry and Its Role in Vision. Neuron. 2015 Sep 23; 87(6):1248-1260. Cao Y, Sarria I, Fehlhaber KE, Kamasawa N, Orlandi C, James KN, Hazen JL, Gardner MR, Farzan M, Lee A, Baker S, Baldwin K, Sampath AP, Martemyanov KA. PMID: 26402607; PMCID: PMC4583715.
      View in: PubMed   Mentions: 55     Fields:    Translation:HumansAnimalsCells
    24. Exchange of Cone for Rod Phosphodiesterase 6 Catalytic Subunits in Rod Photoreceptors Mimics in Part Features of Light Adaptation. J Neurosci. 2015 Jun 17; 35(24):9225-35. Majumder A, Pahlberg J, Muradov H, Boyd KK, Sampath AP, Artemyev NO. PMID: 26085644; PMCID: PMC4469743.
      View in: PubMed   Mentions: 20     Fields:    Translation:HumansAnimalsCells
    25. Sensitivity and kinetics of signal transmission at the first visual synapse differentially impact visually-guided behavior. Elife. 2015 Apr 16; 4:e06358. Sarria I, Pahlberg J, Cao Y, Kolesnikov AV, Kefalov VJ, Sampath AP, Martemyanov KA. PMID: 25879270; PMCID: PMC4412108.
      View in: PubMed   Mentions: 10     Fields:    Translation:AnimalsCells
    26. Detection of single photons by toad and mouse rods. Proc Natl Acad Sci U S A. 2013 Nov 26; 110(48):19378-83. Reingruber J, Pahlberg J, Woodruff ML, Sampath AP, Fain GL, Holcman D. PMID: 24214653; PMCID: PMC3845110.
      View in: PubMed   Mentions: 19     Fields:    Translation:AnimalsCells
    27. Transducin translocation contributes to rod survival and enhances synaptic transmission from rods to rod bipolar cells. Proc Natl Acad Sci U S A. 2013 Jul 23; 110(30):12468-73. Majumder A, Pahlberg J, Boyd KK, Kerov V, Kolandaivelu S, Ramamurthy V, Sampath AP, Artemyev NO. PMID: 23836670; PMCID: PMC3725049.
      View in: PubMed   Mentions: 23     Fields:    Translation:AnimalsCells
    28. Apoptosis regulates ipRGC spacing necessary for rods and cones to drive circadian photoentrainment. Neuron. 2013 Feb 06; 77(3):503-15. Chen SK, Chew KS, McNeill DS, Keeley PW, Ecker JL, Mao BQ, Pahlberg J, Kim B, Lee SC, Fox MA, Guido W, Wong KY, Sampath AP, Reese BE, Kuruvilla R, Hattar S. PMID: 23395376; PMCID: PMC3569737.
      View in: PubMed   Mentions: 22     Fields:    Translation:AnimalsCells
    29. Functional comparison of rod and cone Gα(t) on the regulation of light sensitivity. J Biol Chem. 2013 Feb 22; 288(8):5257-67. Mao W, Miyagishima KJ, Yao Y, Soreghan B, Sampath AP, Chen J. PMID: 23288843; PMCID: PMC3581426.
      View in: PubMed   Mentions: 14     Fields:    Translation:AnimalsCells
    30. Regulators of G protein signaling RGS7 and RGS11 determine the onset of the light response in ON bipolar neurons. Proc Natl Acad Sci U S A. 2012 May 15; 109(20):7905-10. Cao Y, Pahlberg J, Sarria I, Kamasawa N, Sampath AP, Martemyanov KA. PMID: 22547806; PMCID: PMC3356620.
      View in: PubMed   Mentions: 52     Fields:    Translation:AnimalsCells
    31. Dark-adapted response threshold of OFF ganglion cells is not set by OFF bipolar cells in the mouse retina. J Neurophysiol. 2012 May; 107(10):2649-59. Arman AC, Sampath AP. PMID: 22338022; PMCID: PMC3362285.
      View in: PubMed   Mentions: 28     Fields:    Translation:AnimalsCells
    32. Physiological response of normal and RD mouse retinal ganglion cells to electrical stimulation. Annu Int Conf IEEE Eng Med Biol Soc. 2012; 2012:2985-8. Cho AK, Sampath AP, Weiland JD. PMID: 23366552.
      View in: PubMed   Mentions:    Fields:    Translation:AnimalsCells
    33. Perspectives on: information coding in mammalian sensory physiology. J Gen Physiol. 2011 Sep; 138(3):281-2. Farley RA, Sampath AP. PMID: 21875976; PMCID: PMC3171078.
      View in: PubMed   Mentions: 2     Fields:    Translation:HumansAnimalsCells
    34. Virally delivered channelrhodopsin-2 safely and effectively restores visual function in multiple mouse models of blindness. Mol Ther. 2011 Jul; 19(7):1220-9. Doroudchi MM, Greenberg KP, Liu J, Silka KA, Boyden ES, Lockridge JA, Arman AC, Janani R, Boye SE, Boye SL, Gordon GM, Matteo BC, Sampath AP, Hauswirth WW, Horsager A. PMID: 21505421; PMCID: PMC3129568.
      View in: PubMed   Mentions: 119     Fields:    Translation:AnimalsCells
    35. Visual threshold is set by linear and nonlinear mechanisms in the retina that mitigate noise: how neural circuits in the retina improve the signal-to-noise ratio of the single-photon response. Bioessays. 2011 Jun; 33(6):438-47. Pahlberg J, Sampath AP. PMID: 21472740; PMCID: PMC3428150.
      View in: PubMed   Mentions: 22     Fields:    Translation:HumansAnimalsCells
    36. Physiological response of mouse retinal ganglion cells to electrical stimulation: effect of soma size. Annu Int Conf IEEE Eng Med Biol Soc. 2011; 2011:1081-4. Cho AK, Sampath AP, Weiland JD. PMID: 22254501; PMCID: PMC4399765.
      View in: PubMed   Mentions: 4     Fields:    Translation:AnimalsCells
    37. Coordinated control of sensitivity by two splice variants of Gα(o) in retinal ON bipolar cells. J Gen Physiol. 2010 Oct; 136(4):443-54. Okawa H, Pahlberg J, Rieke F, Birnbaumer L, Sampath AP. PMID: 20837674; PMCID: PMC2947061.
      View in: PubMed   Mentions: 18     Fields:    Translation:AnimalsCells
    38. Patch clamp recordings from mouse retinal neurons in a dark-adapted slice preparation. J Vis Exp. 2010 Sep 12; (43). Arman AC, Sampath AP. PMID: 20864928; PMCID: PMC3229218.
      View in: PubMed   Mentions: 9     Fields:    Translation:AnimalsCells
    39. Rod photoreceptors drive circadian photoentrainment across a wide range of light intensities. Nat Neurosci. 2010 Sep; 13(9):1107-12. Altimus CM, Güler AD, Alam NM, Arman AC, Prusky GT, Sampath AP, Hattar S. PMID: 20711184; PMCID: PMC2928860.
      View in: PubMed   Mentions: 116     Fields:    Translation:AnimalsCells
    40. Flow of energy in the outer retina in darkness and in light. Proc Natl Acad Sci U S A. 2010 May 11; 107(19):8599-604. Linton JD, Holzhausen LC, Babai N, Song H, Miyagishima KJ, Stearns GW, Lindsay K, Wei J, Chertov AO, Peters TA, Caffe R, Pluk H, Seeliger MW, Tanimoto N, Fong K, Bolton L, Kuok DL, Sweet IR, Bartoletti TM, Radu RA, Travis GH, Zagotta WN, Townes-Anderson E, Parker E, Van der Zee CE, Sampath AP, Sokolov M, Thoreson WB, Hurley JB. PMID: 20445106; PMCID: PMC2889335.
      View in: PubMed   Mentions: 62     Fields:    Translation:AnimalsCells
    41. Optimal processing of photoreceptor signals is required to maximize behavioural sensitivity. J Physiol. 2010 Jun 01; 588(Pt 11):1947-60. Okawa H, Miyagishima KJ, Arman AC, Hurley JB, Field GD, Sampath AP. PMID: 20403975; PMCID: PMC2901982.
      View in: PubMed   Mentions: 29     Fields:    Translation:AnimalsCells
    42. Photopigment quenching is Ca2+ dependent and controls response duration in salamander L-cone photoreceptors. J Gen Physiol. 2010 Apr; 135(4):355-66. Matthews HR, Sampath AP. PMID: 20231373; PMCID: PMC2847922.
      View in: PubMed   Mentions: 17     Fields:    Translation:AnimalsCells
    43. Functional properties of synaptic transmission in primary sense organs. J Neurosci. 2009 Oct 14; 29(41):12802-6. Singer JH, Glowatzki E, Moser T, Strowbridge BW, Bhandawat V, Sampath AP. PMID: 19828792; PMCID: PMC2788503.
      View in: PubMed   Mentions: 7     Fields:    Translation:HumansAnimalsCells
    44. Setting the absolute threshold of vision. F1000 Biol Rep. 2009 Aug 26; 1:66. Sampath AP, Fain GL. PMID: 20495680; PMCID: PMC2873777.
      View in: PubMed   Mentions: 1  
    45. Metabolic constraints on the recovery of sensitivity after visual pigment bleaching in retinal rods. J Gen Physiol. 2009 Sep; 134(3):165-75. Miyagishima KJ, Cornwall MC, Sampath AP. PMID: 19687232; PMCID: PMC2737229.
      View in: PubMed   Mentions: 6     Fields:    Translation:AnimalsCells
    46. Retina-specific GTPase accelerator RGS11/G beta 5S/R9AP is a constitutive heterotrimer selectively targeted to mGluR6 in ON-bipolar neurons. J Neurosci. 2009 Jul 22; 29(29):9301-13. Cao Y, Masuho I, Okawa H, Xie K, Asami J, Kammermeier PJ, Maddox DM, Furukawa T, Inoue T, Sampath AP, Martemyanov KA. PMID: 19625520; PMCID: PMC2731308.
      View in: PubMed   Mentions: 58     Fields:    Translation:HumansAnimalsCells
    47. ATP consumption by mammalian rod photoreceptors in darkness and in light. Curr Biol. 2008 Dec 23; 18(24):1917-21. Okawa H, Sampath AP, Laughlin SB, Fain GL. PMID: 19084410; PMCID: PMC2615811.
      View in: PubMed   Mentions: 161     Fields:    Translation:AnimalsCells
    48. Targeting of RGS7/Gbeta5 to the dendritic tips of ON-bipolar cells is independent of its association with membrane anchor R7BP. J Neurosci. 2008 Oct 08; 28(41):10443-9. Cao Y, Song H, Okawa H, Sampath AP, Sokolov M, Martemyanov KA. PMID: 18842904; PMCID: PMC2587022.
      View in: PubMed   Mentions: 36     Fields:    Translation:AnimalsCells
    49. Optimization of single-photon response transmission at the rod-to-rod bipolar synapse. Physiology (Bethesda). 2007 Aug; 22:279-86. Okawa H, Sampath AP. PMID: 17699881.
      View in: PubMed   Mentions: 18     Fields:    Translation:HumansAnimalsCells
    50. Controlling the gain of rod-mediated signals in the Mammalian retina. J Neurosci. 2006 Apr 12; 26(15):3959-70. Dunn FA, Doan T, Sampath AP, Rieke F. PMID: 16611812; PMCID: PMC6673884.
      View in: PubMed   Mentions: 114     Fields:    Translation:AnimalsCells
    51. Recoverin improves rod-mediated vision by enhancing signal transmission in the mouse retina. Neuron. 2005 May 05; 46(3):413-20. Sampath AP, Strissel KJ, Elias R, Arshavsky VY, McGinnis JF, Chen J, Kawamura S, Rieke F, Hurley JB. PMID: 15882641.
      View in: PubMed   Mentions: 61     Fields:    Translation:AnimalsCells
    52. Retinal processing near absolute threshold: from behavior to mechanism. Annu Rev Physiol. 2005; 67:491-514. Field GD, Sampath AP, Rieke F. PMID: 15709967.
      View in: PubMed   Mentions: 88     Fields:    Translation:HumansAnimalsCells
    53. Selective transmission of single photon responses by saturation at the rod-to-rod bipolar synapse. Neuron. 2004 Feb 05; 41(3):431-43. Sampath AP, Rieke F. PMID: 14766181.
      View in: PubMed   Mentions: 94     Fields:    Translation:AnimalsCells
    54. Molecular mechanism of spontaneous pigment activation in retinal cones. Biophys J. 2002 Jul; 83(1):184-93. Sampath AP, Baylor DA. PMID: 12080111; PMCID: PMC1302138.
      View in: PubMed   Mentions: 23     Fields:    Translation:AnimalsCells
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