Inactivation of large-conductance, calcium-activated potassium channels in rat cortical neurons

M. A Smith, M.L.J Ashford

    Research output: Contribution to journalArticle

    9 Citations (Scopus)

    Abstract

    Inside-out patch recordings from rat acutely dissociated cerebral cortical neurons revealed time and voltage-dependent activity of a large-conductance calcium-activated potassium channel. Channel activity inactivated within minutes following a depolarizing voltage step, and was recovered from inactivation by membrane hyperpolarization. Inactivation rate was not influenced by internal calcium or membrane voltage; however, reducing channel activity with intracellular calcium destabilized inactivation. Channel inactivation was abolished by intracellular trypsin treatment, suggesting that an associated inactivating particle was responsible for inactivation. Application of alkaline phosphatase to the internal aspect of the patch membrane increased channel activity and abolished channel inactivation, without affecting its voltage and calcium dependence. Internal application of Mg-ATP, but not Mg-5'-adenylylamidodiphosphate, retarded recovery of channel activity from inactivation, whereas internal application of protein phosphatase-1a enhanced recovery from inactivation. The abolition of channel inactivation by alkaline phosphatase was prevented by prior internal tetraethylammonium treatment, indicating that the alkaline phosphatase site is closely associated with the channel pore. These results demonstrate that cortical large-conductance calcium-activated potassium channel inactivation is probably mediated by an endogenous, trypsin-sensitive, inactivation particle. This particle appears to inactivate the open channel and requires a critical phosphate group for stable block. The slow time-course of channel inactivation may have some pathophysiological significance in maintenance of epileptiform activity.

    Original languageEnglish
    Pages (from-to)33-50
    Number of pages18
    JournalNeuroscience
    Volume95
    Issue number1
    DOIs
    Publication statusPublished - Nov 1999

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    Large-Conductance Calcium-Activated Potassium Channels
    Alkaline Phosphatase
    Calcium
    Neurons
    Trypsin
    Tetraethylammonium
    Membranes
    Phosphoprotein Phosphatases
    Ion Channels
    Adenosine Triphosphate
    Phosphates
    Maintenance

    Cite this

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    abstract = "Inside-out patch recordings from rat acutely dissociated cerebral cortical neurons revealed time and voltage-dependent activity of a large-conductance calcium-activated potassium channel. Channel activity inactivated within minutes following a depolarizing voltage step, and was recovered from inactivation by membrane hyperpolarization. Inactivation rate was not influenced by internal calcium or membrane voltage; however, reducing channel activity with intracellular calcium destabilized inactivation. Channel inactivation was abolished by intracellular trypsin treatment, suggesting that an associated inactivating particle was responsible for inactivation. Application of alkaline phosphatase to the internal aspect of the patch membrane increased channel activity and abolished channel inactivation, without affecting its voltage and calcium dependence. Internal application of Mg-ATP, but not Mg-5'-adenylylamidodiphosphate, retarded recovery of channel activity from inactivation, whereas internal application of protein phosphatase-1a enhanced recovery from inactivation. The abolition of channel inactivation by alkaline phosphatase was prevented by prior internal tetraethylammonium treatment, indicating that the alkaline phosphatase site is closely associated with the channel pore. These results demonstrate that cortical large-conductance calcium-activated potassium channel inactivation is probably mediated by an endogenous, trypsin-sensitive, inactivation particle. This particle appears to inactivate the open channel and requires a critical phosphate group for stable block. The slow time-course of channel inactivation may have some pathophysiological significance in maintenance of epileptiform activity.",
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    Inactivation of large-conductance, calcium-activated potassium channels in rat cortical neurons. / Smith, M. A; Ashford, M.L.J.

    In: Neuroscience, Vol. 95, No. 1, 11.1999, p. 33-50.

    Research output: Contribution to journalArticle

    TY - JOUR

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    AB - Inside-out patch recordings from rat acutely dissociated cerebral cortical neurons revealed time and voltage-dependent activity of a large-conductance calcium-activated potassium channel. Channel activity inactivated within minutes following a depolarizing voltage step, and was recovered from inactivation by membrane hyperpolarization. Inactivation rate was not influenced by internal calcium or membrane voltage; however, reducing channel activity with intracellular calcium destabilized inactivation. Channel inactivation was abolished by intracellular trypsin treatment, suggesting that an associated inactivating particle was responsible for inactivation. Application of alkaline phosphatase to the internal aspect of the patch membrane increased channel activity and abolished channel inactivation, without affecting its voltage and calcium dependence. Internal application of Mg-ATP, but not Mg-5'-adenylylamidodiphosphate, retarded recovery of channel activity from inactivation, whereas internal application of protein phosphatase-1a enhanced recovery from inactivation. The abolition of channel inactivation by alkaline phosphatase was prevented by prior internal tetraethylammonium treatment, indicating that the alkaline phosphatase site is closely associated with the channel pore. These results demonstrate that cortical large-conductance calcium-activated potassium channel inactivation is probably mediated by an endogenous, trypsin-sensitive, inactivation particle. This particle appears to inactivate the open channel and requires a critical phosphate group for stable block. The slow time-course of channel inactivation may have some pathophysiological significance in maintenance of epileptiform activity.

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