Calcium is necessary for light excitation in barnacle photoreceptors |
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Authors: | Uri Werner Edith Suss-Toby Ayelet Rom Baruch Minke |
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Affiliation: | (1) Department of Physiology and the Minerva Center for Studies of Visual Transduction, The Hebrew University-Hadassah Medical School, 91010 Jerusalem, Israel |
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Abstract: | Summary Illumination of barnacle (Balanus amphitrite) photoreceptors is known to increase the membrane permeability to sodium and Ca2+ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La3+), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca2+ by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca2+, but not K+ into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La3+. The EGTA experiments suggest that internal Ca2+ is necessary for light excitation of barnacle photoreceptors while the La3+ experiments suggest that La3+-sensitive inward current is necessary to maintain excitation during prolonged light.Abbreviations EGTA ethylenglyol-bis-(-aminoethylether) N, N, N1, N1-tetraacetate - BAPTA bis-(0-aminophenoxy)-ethane-N, N, N1, N1-tetraacetic acid - DMSO dimethyl sulfoxide - trp transient receptor potential - nss no steady state - ASW artificial sea water |
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Keywords: | Balanus Lanthanum EGTA trp mutant |
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