April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
Multiple Sweet Sensing Systems In Rat Retina
Author Affiliations & Notes
  • Jaeyoung Yang
    Neuroscience, SUNY Buffalo, Amherst, New York
  • Jason Myers
    Neuroscience, SUNY Buffalo, Amherst, New York
  • Malcolm M. Slaughter
    Physiology & Biophysics, SUNY at Buffalo, Buffalo, New York
  • Footnotes
    Commercial Relationships  Jaeyoung Yang, None; Jason Myers, None; Malcolm M. Slaughter, None
  • Footnotes
    Support  NEI 05725
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 4133. doi:
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      Jaeyoung Yang, Jason Myers, Malcolm M. Slaughter; Multiple Sweet Sensing Systems In Rat Retina. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4133.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : Sweet taste receptors (STRs) are expressed in various tissues including gut, pancreas, and hypothalamus. We determined the molecular and physiological characteristics of sweet sensing mechanisms in rat retina.

Methods: : Acutely dissociated or cultured retinal cells from 10 - 16 day Sprague-Dawley rats were treated with various superfused drugs. Internal calcium was monitored using fluo3-based imaging while calcium currents were measured using whole cell patch clamp. Single cell RT-PCR and RACE (rapid amplification of cDNA Ends) were used to determine STR expression. Gene knockdown of T1R2 was done in a retinal cell line, R28.

Results: : We found mRNA of T1R1 (umami TR) and T1R2 (sweet TR) expressed in rat retina but T1R3 was not detected. In fluo3 calcium imaging, various sweeteners including aspartame, saccharin, D-amino acids, and glucose raised intracellular calcium in isolated retinal neurons. The full sequences of T1R1 and T1R2 from rat retina were identical to T1R1 and T1R2 of tongue. Yet rat T1R2 in the tongue does not respond to aspartame. In single cell RT-PCR analysis, aspartame responding neurons have both T1R1 and T1R2. But when T1R1 and T1R2 were transfected into HEK293 cells with GIRK and Galpha15, these cells did not respond to sweeteners. In gene knockdown experiments with siRNA against T1R2 in R28 cells, the response to 1mM saccharin was reduced 45% compared to controls, but the response to 1mM aspartame remained. This suggests T1R2 in rat retina is functionally similar to tongue. Part of the aspartame response is mediated by calcium permeable membrane channel s because it could be eliminated by removing extracellular calcium. TRPV1 blockers (10µM SB366791) blocked aspartame’s action and part of the glucose response in rat retina. Cells sensitive to the TRPV1 blocker were not sensitive to capsaicin, suggesting an aspartame-sensitive and capsaicin-insensitive sweet sensing response. Aspartame also altered the ERG b-wave amplitude.

Conclusions: : There are multiple sweet sensing pathways in retina, including the canonical T1R2 system found in tongue and a TRPV1 system. Saccharin is detected by the former, aspartame by the latter.

Keywords: receptors • ion channels • retinal connections, networks, circuitry 
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