PMID: 9444299Jan 28, 1998Paper

Ion channel and exchange currents in single myocytes isolated from the rabbit atrioventricular node

The Canadian Journal of Cardiology
J C Hancox, J S Mitcheson

Abstract

To review findings from the authors' laboratory in studies of electrophysiological properties of single rod- and spindle-shaped myocytes from rabbit atrioventricular node (AVN). Single cells were isolated from the AVN of the rabbit heart with the use of enzymatic and mechanical dispersion. For recording, cells were superfused with a Tyrode's solution at 33 to 37 degrees C, and recordings were made with microelectrodes or patch pipettes under 'current' or voltage' clamp conditions. Results are expressed as mean +/- SEM. AVN cells had a mean membrane capacitance of 40 +/- 3.9 pF and membrane resistance of 565 +/- 167 M omega (n = 9). Spontaneously active cells exhibited pacemaker activity showing a clear diastolic depolarization and overshooting action potential (AP) with a relatively slow upstroke velocity (7.4 +/- 0.9 V/s, n = 6) and a maximum diastolic potential of -70.5 +/- 2.9 mV. Under voltage clamp conditions, depolarizing pulses from 40 mV elicited L-type calcium currents sensitive to inhibition by nifedipine and managanese or cadmium ions, which could also block spontaneous APs. Depolarizing pulses also activated delayed rectifier potassium current (IK). IK showed rapid activation, and IK 'tails' in AVN cells were blocke...Continue Reading

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