Monovalent amidiniums block calcium channels in chick sensory neurons |
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Authors: | S. L. Mironov |
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Affiliation: | (1) Max-Planck-Institute for Psychiatry, Am Klopferspitz 18a, 82142 Planegg-Martinsried, Germany;(2) Present address: Department of Animal Physiology, Salzburg University, Institute for Zoology, Hellbrunnerstr. 34, A-5020 Salzburg, Austria |
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Abstract: | The effect of amidiniums on high-threshold Ca2+ channel currents (ICa) was studied in chick dorsal root ganglion neurons. Guanidinium reduced ICa in a dose-dependent fashion. The block was relieved by increasing the concentration of the permeant ions, Ba2+ or Ca2+, suggesting a competition for a common binding site within the channel. Formamidinium and methyl-guanidinium suppressed ICa with similar potencies, whereas l-arginine had no effect. A neutral amidine, urea, increased ICa. In Ca2+-free solutions guanidinium and Na+ permeated through the Ca2+ channel equally well. Structure-activity relationship obtained for blocking efficacies of different amidiniums are used to discuss possible configurations of the selectivity filter in the Ca2+ channel.The author wishes to thank Ms. S. Engers for the cell isolation and making of the electrodes. |
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Keywords: | Ca2+ channel Amidiniums Block and permeability Selectivity filter |
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