A: Acute slice of left ventricular muscle from an adult rat (thickness=250μm) placed in a MED-P545A Probe (450μm inter-polar distance).

B: Paced responses evoked by a 100μA electrical stimulus at the two electrodes (49 &50) on the MED Probe (marked in red in the left picture) in the absence (pink), presence (green) of 100μM Quinidine.

C: Detailed view of evoked responses obtained at channel 22. In the presence of 100μM Quinidine, the latency and duration of the action potentials were prolonged, and the slope of the rising phase decreased (purple). These affects were almost completely reversed after wash out (green). The pre-drug response is shown in blue.