Figure 5.

Frequency-dependent effects of dofetilide and propranolol on twitch tension in right ventricular papillary muscles of rabbits (a) and guinea-pigs (b). After measuring baseline values, separate groups of tissues were treated with propranolol (300 nM), dofetilide (100 nM), dofetilide+propranolol (Dof+Prop) or were used as control. Each incubation period lasted for 30 min. Values are means±s.e.m., n indicates the number of experiments. Asterisks (***P<0.001) denote significant differences vs control at the same frequency.