What does this research mean for the field?

The pace-maker current in cardiac Purkinje cells is an inward current carried by Na and K ions that activates upon hyperpolarization, contradicting previous assumptions based on intact fibers. Novelty: ClaimNovelty.CONTRADICTORY. Consensus alignment: ConsensusAlignment.CHALLENGES_CONSENSUS.

What question did this study set out to answer?

Characterize the basic electrophysiological properties and determine the ionic mechanism of the pacemaker current in isolated mammalian cardiac Purkinje cells.

April 1, 1984The Journal of PhysiologyOpen Access

Single cardiac Purkinje cells: general electrophysiology and voltage‐clamp analysis of the pace‐maker current.

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Characterize the basic electrophysiological properties and determine the ionic mechanism of the pacemaker current in isolated mammalian cardiac Purkinje cells.
Enzymatically isolated single Purkinje cells from dog, sheep, and cow hearts using calcium-free collagenase Tyrode solution.
Recorded action potentials, resting potentials, and sensitivity to potassium, catecholamines, and tetrodotoxin.
Conducted two-microelectrode voltage-clamp recordings to evaluate the pacemaker current under exposure to cesium, barium, and adrenaline.
Isolated cells exhibited maximum diastolic potentials of -70 to -85 mV, specific membrane resistances of 21-32 kΩ·cm², and maximum upstroke velocities of 150-750 V/s.
The pacemaker current was blocked in a voltage-dependent manner by 1 mM cesium, unaffected by 1 mM barium, and shifted toward depolarizing potentials by adrenaline.
Unlike intact tissue preparations, the single-cell pacemaker current did not reverse negative to -50 mV, demonstrating that it is an inward current carried by sodium and potassium ions activating upon hyperpolarization.

Structured PICO

Population

Single Purkinje cells isolated from dog, sheep and cow hearts

Intervention

Voltage-clamp analysis and pharmacological interventions (tetrodotoxin, catecholamines, 1 mM-Cs, 1 mM-Ba, varying external K concentrations)

Outcome

Electrophysiological properties and ionic nature of the pace-maker currentsurrogate

Voltage-clamp analysis of isolated single cardiac Purkinje cells suggests the pace-maker current is an inward current carried by Na and K ions that activates upon hyperpolarization.

Discussion

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Implication

Challenges reversal estimates from intact fibres; leaves open the Na/K basis of pacemaker current pending further validation.

Cite This Study

Callewaert et al. (1984) studied this question.

synapsesocial.com/papers/6a1bf8811567d2fc4d5f5931 https://doi.org/10.1113/jphysiol.1984.sp015179

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Single cardiac Purkinje cells: general electrophysiology and voltage‐clamp analysis of the pace‐maker current.

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Single cardiac Purkinje cells: general electrophysiology and voltage‐clamp analysis of the pace‐maker current.

Key Points

Structured PICO

Discussion

Implication

Cite This Study

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