Muscarinic and beta-adrenergic depression of the slow Ca2(+)-activated potassium conductance in hippocampal CA3 pyramidal cells is not mediated by a reduction of depolarization-induced cytosolic Ca2+ transients. |
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| Authors: | T Kn pfel, I Vranesic, B H G hwiler, D A Brown |
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| Affiliation: | Brain Research Institute, University of Zürich, Switzerland. |
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| Abstract: | ![]()
Combined intracellular and microfluorometric recording techniques were used to evaluate whether the inhibition by cholinergic or adrenergic transmitters of the Ca2(+)-activated potassium current (IAHP) in hippocampal CA3 pyramidal cells was mediated by an alteration of depolarization-induced change in cytosolic free Ca2+ concentration [(Ca2+]i). Low concentrations of isoproterenol (1-10 microM) and muscarine (0.25-1 microM) reversibly abolished IAHP without affecting concomitant Ca2+ transients or the steady-state [Ca2+]i. Only after application of higher concentrations of muscarine, [Ca2+]i increased; in the presence of potassium channel blockers, muscarine depressed Ca2+ currents and concomitant Ca2+ transients. These observations provide direct evidence that the inhibition of IAHP by isoproterenol and muscarine are not mediated by an alteration of Ca2+ dynamics. |
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