Ventricular Slices of Adult Mouse Hearts - a new Multicellular In Vitro Model for Electrophysiological Studies
Aim: We established a preparation of adult murine ventricular slices suitable for electrophysiological recordings as a new in vitro model of adult myocardium with preserved in vivo tissue structure. Methods: Short axis slices (thickness: 150 µm) of adult murine ventricles were prepared with a microtome. Sharp glass electrodes were used for measurements of action potentials (APs) at stimulation frequencies of 2 Hz and 10 Hz. Field potential (FP) recordings by means of microelectrode arrays (MEAs) were performed to map excitation spread. Results: APs showed the characteristics of adult murine ventricular APs: (i) a stable resting membrane potential, (ii) a fast upstroke and (iii) a fast phase 1 repolarization. Application of the Na+ channel blocker lidocaine (30 µM) led to a decline of upstroke slope, amplitude and conduction speed. The unspecific K+ channel blocker 4-aminopyridine (5 mM) caused a prolongation of APD50. The excitation spread was homogenous throughout the ventricular wall. Conclusion: Adult murine ventricular slices are electrophysiologically intact and respond physiologically to cardioactive drugs. Thus, they provide a new multicellular in vitro model of adult cardiac tissue suitable for electrophysiological investigations, which in future could be used to study the functional integration of stem cells transplanted in infarcted hearts in vivo.