Inhibition of large-conductance Ca(2+)-activated K(+) channels in hippocampal neurons by toosendanin

Neuroscience
Z F Wang, Y L Shi

Abstract

The effect of toosendanin, a selective presynaptic blocker and effective antibotulismic agent, on large-conductance Ca(2+)-activated K(+) channels was studied in inside-out patches of pyramidal neurons freshly isolated from the hippocampal CA1 region of the rat. Toosendanin (1 x 10(-6)g/ml approximately 1 x 10(-4)g/ml) was found to inhibit large-conductance Ca(2+)-activated K(+) channels by reducing its open probability significantly in a concentration-dependent manner, although the effective concentration of toosendanin was lower in a symmetrical K(+) (150 mM) solution than under asymmetrical conditions (changing K(+) concentration in pipette solution to 5mM). The action was partially reversible by washing. By decreasing the slow open time constant, toosendanin shortened the open dwell time of large-conductance Ca(2+)-activated K(+) channels in a dose-dependent manner. A dose-dependent reduction of unitary current amplitude of the channel was detected after toosendanin perfusion. On elevating the intracellular free calcium concentration from 1 to 10 microM, a similar effect on large-conductance Ca(2+)-activated K(+) channels by toosendanin was also observed, but its efficacy was diminished. These results show that toosendanin ...Continue Reading

References

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Citations

Jan 22, 2003·Luminescence : the Journal of Biological and Chemical Luminescence·Yong A YuKerby Oberg
Jun 10, 2011·Cellular and Molecular Neurobiology·Xiao Feng Fang, Zong Jie Cui
Feb 8, 2003·Neuroscience Research·Mian-Zhi TangYu-Liang Shi
Dec 21, 2005·Acta Pharmacologica Sinica·Mu-feng Li, Yu-liang Shi
Mar 17, 2007·Progress in Neurobiology·Yu-Liang Shi, Mu-Feng Li
Dec 8, 2004·Toxicon : Official Journal of the International Society on Toxinology·Mu-Feng Li, Yu-Liang Shi
Oct 16, 2002·World Journal of Gastroenterology : WJG·Zong-Jie Cui, Xue-Hui He

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