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Thor Eysteinsson, Gudmundur Jonsson; Stimulation or blockage of the retinal A1 adenosine receptors modifies the components of the rat electroretinogram. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):472.
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© ARVO (1962-2015); The Authors (2016-present)
Adenosine is a neuromodulator found in various areas of the central nervous system, including the retina. It has been suggested that adenosine may serve a neuroprotective role in the retina, based on electroretinogram (ERG) recordings from rat retinae. We have previously found that A2a and A3 receptors in the retina can modify the components of the rat ERG. The purpose of this study was to assess the putative role of A1 adenosine receptors, known to be present in the rat retina, in generation and modulation of the rat ERG.
Sprague Dawley rats were anesthetized by an intraperitoneal injection of S-ketamine (75mg/kg) and xylazine (6mg/kg). The flash ERG was recorded between an electrode placed on the cornea and a reference electrode on the lower canthus. An agonist and antagonist for A1 receptors were each injected (5 µL) into the vitreous of six eyes with a NanoFil IOKit system (World Precision Instruments, Inc, USA). Their effects on the components of the scotopic and photopic ERGs were examined, along with ERG flicker responses.
The A1 agonist CPA [1 mM] increased the mean amplitude of the a-wave (70.7 + 31.3 µV to 96 + 28.2 µV; p=0.042), with insignificant increase in the mean amplitude of the scotopic b-wave (180.3 + 83.3 µV to 177.7 + 64.1 µV; p=0.923), and a decrease in the mean amplitude of the photopic b-wave (143.4 + 39.8 µV to 90.3 + 37 µV; p=0.002), but no effect on the flicker ERG response. The A1 antagonist DPCPX [0.5 mM] decreased the mean amplitude of both the scotopic (198.0 + 67.3 µV to 123.7 µV + 86.6 µV; p=0.004) and photopic b-waves (139.2 + 35.7 µV to 65.0 + 41.5 µV; p=0.013). DPCPX also decreased the mean amplitude of the oscillatory potentials (63.2 + 23.1 µV to 26.3 + 36.9 µV; p=0.025), and the photopic flicker response (62.3 ± 18.7 µV to 30.0 ± 15.4 µV (p=0.029)).
Retinal neurons that contain A1 adenosine receptors contribute to the generation of the photopic and scotopic rat ERG a- and b-waves, and oscillatory potentials.
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