45Ca2+ Uptake into Rat Whole Brain Synaptosomes Unaltered by Dihydropyridine Calcium Antagonists |
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Authors: | Laura C. Daniell Edward M. Barr Steven W. Leslie |
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Affiliation: | Division of Pharmacology, College of Pharmacy, University of Texas at Austin, Austin, Texas, U.S.A. |
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Abstract: | Abstract: Voltage-dependent 45Ca2+ uptake into rat whole brain synaptosomes was measured after 3-s KCl-induced depolarization to investigate possible inhibitory effects of calcium antagonists, nitrendipine, nimodipine, and nisoldipine. At a Ca2+ concentration of 1.2 m M , nitrendipine, in concentrations ranging from 0.1 n M to 10 μ M , had no effect on 45Ca2+ uptake. When the Ca2+ concentration was lowered to 0.06 and 0.12 m M , nitrendipine, 10 μ M , inhibited 45Ca2+ uptake in response to 109 m M KCl depolarization. However, in a separate concentration response study, nitrendipine, nimodipine, and nisoldipine, 0.1 n M to 10 μ M , failed to alter the uptake of 45Ca2+ (0.06 m M Ca2+) into 30 m M KCl-depolarized synaptosomes. The high concentrations of these agents required to depress 45Ca2+ uptake indicate that the dihydropyridine calcium antagonists are considerably less potent in brain tissue than in peripheral tissue. |
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Keywords: | Calcium antagonists Calcium uptake Nitrendipine Nimodipine Nisoldipine |
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