The action of high K+ and aglycaemia on the electrical properties and synaptic transmission in rat intracardiac ganglion neurones in vitro

Jhansi Dyavanapalli, Katrina Rimmer, Alexander A. Harper

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    We have investigated the action of two elements of acute ischaemia, high potassium and aglycaemia, on the electrophysiological properties and ganglionic transmission of adult rat intracardiac ganglion (ICG) neurones. We used a whole-mount ganglion preparation of the right atrial ganglion plexus and sharp microelectrode recording techniques. Increasing extracellular K+ from its normal value of 4.7 mm to 10 mm decreased membrane potential and action potential after-hyperpolarization amplitude but otherwise had no effect on postganglionic membrane properties. It did, however, reduce the ability of synaptically evoked action potentials to follow high-frequency (100 Hz) repetitive stimulation. A further increase in K+ changed both the passive and the active membrane properties of the postganglionic neurone: time constant, membrane resistance and action potential overshoot were all decreased in high K+ (20 mm). The ICG neurones display a predominantly phasic discharge in response to prolonged depolarizing current pulses. High K+ had no impact on this behaviour but reduced the time-dependent rectification response to hyperpolarizing currents. At 20 mm, K+ practically blocked ganglionic transmission in most neurones at all frequencies tested. Aglycaemia, nominally glucose-free physiological saline solution (PSS), increased the time constant and membrane resistance of ICG neurones but otherwise had no action on their passive or active properties or ganglionic transmission. However, the combination of aglycaemia and 20 mm K+ displayed an improvement in passive properties and ganglionic transmission when compared with 20 mm K+ PSS. These data indicate that the presynaptic terminal is the primary target of high extracellular potassium and that aglycaemia may have protective actions against this challenge.

    Original languageEnglish
    Pages (from-to)201-212
    Number of pages12
    JournalExperimental Physiology
    Volume94
    Issue number2
    DOIs
    Publication statusPublished - 1 Feb 2009

    Keywords

    • DEVELOPMENTAL-CHANGES
    • ELECTROPHYSIOLOGICAL PROPERTIES
    • EXTRACELLULAR POTASSIUM
    • MEMBRANE-PROPERTIES
    • CARDIAC-FUNCTION
    • HEART-RATE
    • CURRENTS
    • NERVE
    • ISCHEMIA
    • STIMULATION

    Cite this

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    title = "The action of high K+ and aglycaemia on the electrical properties and synaptic transmission in rat intracardiac ganglion neurones in vitro",
    abstract = "We have investigated the action of two elements of acute ischaemia, high potassium and aglycaemia, on the electrophysiological properties and ganglionic transmission of adult rat intracardiac ganglion (ICG) neurones. We used a whole-mount ganglion preparation of the right atrial ganglion plexus and sharp microelectrode recording techniques. Increasing extracellular K+ from its normal value of 4.7 mm to 10 mm decreased membrane potential and action potential after-hyperpolarization amplitude but otherwise had no effect on postganglionic membrane properties. It did, however, reduce the ability of synaptically evoked action potentials to follow high-frequency (100 Hz) repetitive stimulation. A further increase in K+ changed both the passive and the active membrane properties of the postganglionic neurone: time constant, membrane resistance and action potential overshoot were all decreased in high K+ (20 mm). The ICG neurones display a predominantly phasic discharge in response to prolonged depolarizing current pulses. High K+ had no impact on this behaviour but reduced the time-dependent rectification response to hyperpolarizing currents. At 20 mm, K+ practically blocked ganglionic transmission in most neurones at all frequencies tested. Aglycaemia, nominally glucose-free physiological saline solution (PSS), increased the time constant and membrane resistance of ICG neurones but otherwise had no action on their passive or active properties or ganglionic transmission. However, the combination of aglycaemia and 20 mm K+ displayed an improvement in passive properties and ganglionic transmission when compared with 20 mm K+ PSS. These data indicate that the presynaptic terminal is the primary target of high extracellular potassium and that aglycaemia may have protective actions against this challenge.",
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    author = "Jhansi Dyavanapalli and Katrina Rimmer and Harper, {Alexander A.}",
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    The action of high K+ and aglycaemia on the electrical properties and synaptic transmission in rat intracardiac ganglion neurones in vitro. / Dyavanapalli, Jhansi; Rimmer, Katrina; Harper, Alexander A.

    In: Experimental Physiology, Vol. 94, No. 2, 01.02.2009, p. 201-212.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - The action of high K+ and aglycaemia on the electrical properties and synaptic transmission in rat intracardiac ganglion neurones in vitro

    AU - Dyavanapalli, Jhansi

    AU - Rimmer, Katrina

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    AB - We have investigated the action of two elements of acute ischaemia, high potassium and aglycaemia, on the electrophysiological properties and ganglionic transmission of adult rat intracardiac ganglion (ICG) neurones. We used a whole-mount ganglion preparation of the right atrial ganglion plexus and sharp microelectrode recording techniques. Increasing extracellular K+ from its normal value of 4.7 mm to 10 mm decreased membrane potential and action potential after-hyperpolarization amplitude but otherwise had no effect on postganglionic membrane properties. It did, however, reduce the ability of synaptically evoked action potentials to follow high-frequency (100 Hz) repetitive stimulation. A further increase in K+ changed both the passive and the active membrane properties of the postganglionic neurone: time constant, membrane resistance and action potential overshoot were all decreased in high K+ (20 mm). The ICG neurones display a predominantly phasic discharge in response to prolonged depolarizing current pulses. High K+ had no impact on this behaviour but reduced the time-dependent rectification response to hyperpolarizing currents. At 20 mm, K+ practically blocked ganglionic transmission in most neurones at all frequencies tested. Aglycaemia, nominally glucose-free physiological saline solution (PSS), increased the time constant and membrane resistance of ICG neurones but otherwise had no action on their passive or active properties or ganglionic transmission. However, the combination of aglycaemia and 20 mm K+ displayed an improvement in passive properties and ganglionic transmission when compared with 20 mm K+ PSS. These data indicate that the presynaptic terminal is the primary target of high extracellular potassium and that aglycaemia may have protective actions against this challenge.

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    KW - MEMBRANE-PROPERTIES

    KW - CARDIAC-FUNCTION

    KW - HEART-RATE

    KW - CURRENTS

    KW - NERVE

    KW - ISCHEMIA

    KW - STIMULATION

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