EFFECTS OF EXTRACELLULAR Ca2+ CONCENTRATION AND PAPAVERINE ON THE VISUAL CELL FUNCTION IN THE ISOLATED FROG RETINA |
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Authors: | Isao Hanawa Tetsuji Matsuura |
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Institution: | Department of Physiology, Kobe University School of Medicine, Ikuta-ku, Kobe 650 Japan;*Department of Physiology, Kinki University School of Medicine, Sayama, Osaka 589, Japan |
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Abstract: | Abstract— Effects of extracellular Ca2+ concentration and papaverine on the PIII response of the electroretinogram and the dark adaptation process of the visual cells were studied in the isolated, aspartate-treated bullfrog retina. The amplitudes of both the fast and slow PIII responses are increased in 0.01 m M Ca2+ solution, but decreased in Ca2+-free solution containing 1 m M EDTA. The application of 0.1 m M papaverine in the presence of 1 m M Ca2+ led to the enhancement of the slow PIII response at lower stimulus intensity and the prolongation of the slow PIII response, but these effects of papaverine on the response were lost when Ca2+ was removed from the bathing fluid. The half-time of recovery of the fast PIII response amplitude after switching off the adapting light was a linear function of the amount of bleached rhodopsin. Papaverine in the absence of Ca2+ produced about 2-fold increase in the half-time of recovery of the response. These findings suggest that chemical reactions which are sensitive to papaverine in the absence of Ca2+ are implicated in the dark adaptation process of the visual cells. |
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