Figure 2.

Frequency-dependent effects of dofetilide and propranolol on the effective refractory period in atria obtained from reserpinised guinea-pigs. Reserpine (5 mg kg⁻¹ i.p.) was administered 24 h before the experiments. After measuring baseline values, separate groups of preparations were treated with propranolol (300 nM), dofetilide (100 nM), dofetilide+propranolol (Dof+Prop) or were used as control. Each drug was applied for 30 min. Values are means±s.e.m., n indicates the number of experiments. Data are expressed as percentage changes in comparison with the baseline values. No significant changes were observed between the dofetilide- and the dofetilide+propranolol-treated groups.