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Kinematics and EMG

開催日 2014/9/11
時間 11:00 - 12:00
会場 Poster / Exhibition(Event Hall B)

Contributing factors to the polarity determination of surround responses in bipolar cells of the mouse retina

  • P1-109
  • 尹 成珠 / Chengzhu Yin:1 金田 誠 / makoto kaneda:1 
  • 1:日本医科大学 / Department of physiology,Nippon Medical School,  

In the mouse retina, the reversal potential of Cl-(ECl) is different between ON- and OFF- bipolar cells. The difference of ECl favors for the hypothesis that the difference of the reversal potential of GABA responses (EGABA) produces the opposite polarity of surround responses between ON- and OFF-bipolar cells. Another line of evidence shows that the expression patterns of the GABAA and GABAC receptors are different among bipolar cells subtypes. However, it has not been studied whether such a differences of the expression patterns of GABA receptor subtypes can contribute to the difference of EGABA, since EGABA is determined by the combination of ECl and the reversal potential of HCO3-. In the present study, we examined a possibility that the differences of permeability to HCO3-in GABA receptor subtypes are involved in the determination of EGABA by the whole cell patch clamp technique. We also examined whether current hypothesis is sufficient to explain the opposite polarity of surround responses by perforated patch clamp techniques. The reversal potential of GABAA and GABAC receptors were not different in the presence (GABAA: -4.5±5.7 mV, n=6; GABAC: -2.6±3.4 mV, n=5) and the absence (GABAA: -5±3.5 mV, n=6; GABAC: -3.8±4.8 mV, n=5) of extracellular HCO3-(24 mM). We found that the ECl of soma(-18±7.5 mV, n=6) was higher than that of axon terminal(-42±6.2 mV, n=6) in rod bipolar cells. The intracellular Cl-concentration gradient was disappeared and ECl shifted to negative direction (-57±4.3 mV, n=3) when 50µM bumetanide, a NKCC1 antagonist, were applied. These results show that the differences in the distribution of GABA receptor subtypes and the permeability of HCO3- do not contribute to the polarity determination of the surround responses of the bipolar cells, rather that the intracellular Cl-concentration controlled by the Cl-transporter determines the polarity of surround responses.

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