What question did this study set out to answer?

To determine the ionic basis and channel mechanisms underlying the hyperpolarization-activated pacemaker current in rabbit sino-atrial node tissue.

October 1, 1984The Journal of PhysiologyOpen Access

Ionic currents responsible for the generation of pace‐maker current in the rabbit sino‐atrial node.

View Full Paper

Ask AI

Bookmark

To determine the ionic basis and channel mechanisms underlying the hyperpolarization-activated pacemaker current in rabbit sino-atrial node tissue.
Applied a single sucrose-gap voltage-clamp technique to rabbit sino-atrial nodal tissue strips.
Evaluated current and membrane potential responses under hyperpolarizing and depolarizing voltage steps.
Tested the effects of ion removal (sodium and calcium) and pharmacological blockers, including tetrodotoxin, calcium-channel blockers, cesium, barium, and tetraethylammonium.
Total removal of sodium completely abolished the pacemaker current (delta Ip) and hyperpolarized the membrane, while tetrodotoxin and calcium-channel blockers caused no significant changes in delta Ip voltage dependence.
Low concentrations of cesium (< 5 mM) markedly suppressed delta Ip activation, reduced membrane conductance, and slightly slowed pacing rate, whereas barium and tetraethylammonium did not affect activation.
A double-pulse clamp protocol revealed a time-dependent current component that reversed near the potassium equilibrium potential in 50% of experiments, showing secondary involvement of potassium conductance.

Population

Rabbit sino-atrial node strips

Intervention

Application of ion channel blockers (tetrodotoxin, Ca2+-channel blockers, Cs+, Ba2+, tetraethylammonium) and ion removal (Ca2+, Na+)

Comparator

Baseline conditions

Outcome

Pace-maker current (delta Ip, If, Ih) and maximum diastolic potentialsurrogate

The pace-maker current in the rabbit sino-atrial node is primarily carried by Na+ and is blocked by Cs+.

No takes yet. Share an insight, caveat, or question.

Characterizes Na+ dependence of rabbit SAN pacemaker current; leaves open translation to human sinoatrial node physiology.

Maylie et al. (1984) studied this question.

View Full Paper

Ask AI

Bookmark