April 2010
Volume 51, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2010
Histamine Effects on Dopaminergic Amacrine Cells
Author Affiliations & Notes
  • R. Frazao
    Neurobiology and Anatomy, Ut Medical School at Houston, Dallas, Texas
  • R. Heidelberger
    Neurobiology and Anatomy, Ut Medical School at Houston, Dallas, Texas
  • D. W. Marshak
    Neurobiology and Anatomy, Ut Medical School at Houston, Dallas, Texas
  • Footnotes
    Commercial Relationships  R. Frazao, None; R. Heidelberger, None; D.W. Marshak, None.
  • Footnotes
    Support  The National Council for Scientific and Technological Development- Brazil (CNPq); NIH Grants EY06472 and EY012128
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 1854. doi:
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    • Get Citation

      R. Frazao, R. Heidelberger, D. W. Marshak; Histamine Effects on Dopaminergic Amacrine Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1854.

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Abstract

Purpose: : The experiments were designed to test the hypothesis that dopaminergic amacrine cells are among the targets of histamine released from retinopetal axons in mouse retina.

Methods: : Dopaminergic amacrine cells were isolated from transgenic mice (C57BL/TH::RFP), expressing red fluorescent protein and plated onto glass coverslips. Cells were loaded for 45 minutes in darkness at 22° C with Fura 2 acetoxymethyl ester (1 µM), and then the coverslips were mounted on the stage of an inverted microscope with epifluorescent illumination. The cells were superfused with HEPES-buffered saline solutions containing histamine, histamine receptor 1 (HR1) antagonists or agonists in a moist oxygen atmosphere at 20 °C. Free intracellular calcium was determined from the ratio of the fluorescence signals excited at the wavelengths 360 and 380 nm. Mean calcium levels were analyzed using paired t-tests.

Results: : Superfusion of histamine leads to an increase in mean [Ca++]i of the dopaminergic amacrine cells. The effect was dose-dependent and maximal at 5 µM. Superfusion of 5µM histamine produced an increase in mean [Ca++]i in 79% of the cells analyzed; the increase in mean [Ca++]i was 65%, on average with this dose. The HR1 antagonist pyrilamine blocked the effects of 5 µM histamine when applied at 50 µM. The selective HR1 agonist 2-(3-trifluoromethylphenyl) histamine dihydrogenmaleate applied at 5 µM significantly increased mean [Ca++]i.

Conclusions: : The results indicate that the effects of histamine on the dopaminergic cells are mediated by HR1, as predicted in a recent anatomical study of mouse retina.

Keywords: dopamine • amacrine cells • calcium 
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