Figure 4.

Effect of (−) chromanol 293B on rate adaptation of the action potential during β-adrenoceptor stimulation in beagle dog Purkinje fibres – an ‘across stimulation rate' analysis (see Methods). (a) The mean per cent change in APD₉₀ induced by isoproterenol (Iso) alone or when combined with 10 μM (−) chromanol 293B (293B) at a stimulation rate of 3.33 Hz in both female and male animals (n=4 for each gender). ^NSP>0.05. (b) The mean per cent change in APD₉₀ induced by Iso alone or when combined with 10 μM 293B at a stimulation rate of 0.2 Hz in both F and M animals (n=4 for each gender). ^NSP>0.05, ^*P<0.05, ^**P<0.01.