Recordings of (action potential) AP and triggered activity in
single atrial myocytes
Quiescent and Ca2+-tolerant atrial myocytes were
selected for recording APs, delayed afterdepolarizations (DADs) and
early afterdepolarizations (EADs) were elicited in the whole-cell
patch-clamp configuration using a HEKA EPC-10 patch master amplifier.
Atrial myocytes were bathed and perfused (2-3 ml/min) in a bath solution
containing the following reagents (in mM; Sigma-Aldrich, MA, USA): 144
NaCl, 5.6 KCl, 1.2 MgCl2, 5 HEPES, 1.8
CaCl2, 11 Glucose at pH=7.4 titrated with NaOH and
maintained temperature at 22-24 °C. The patch pipette solution contained
the following reagents
(in
mM; Sigma, USA: 110 K-aspartate, 30 KCl, 5 NaCl, 10 HEPES, 0.1 EGTA, 5
Mg-ATP, 5 creatine phosphate, and 0.05 cAMP) at pH=7.2 titrated with
KOH. When filled with pipette solution, the electrode resistance was in
the range of 3-5 MΩ. APs were induced in current-clamp mode by 1.5-fold
diastolic threshold-current pulses of 5-ms duration at a 1000-ms pacing
cycle lengths. EADs were elicited by changing the stimulation frequency
to 0.25 Hz, and DADs were determined following a baseline pacing CL of
9000 ms and 15 beats with a stimulation frequency of 2.5 Hz.