Role of action potential shortening in the prevention of @entity943 in XXXX cardiac tissue.

@entity3529 @entity235 @entity6335 @entity72754 @entity141 @entity943 @entity5140 @entity66783
1. The effects of the K+ channel opener @entity6335 and the @entity5140 -containing @entity141 and @entity3529 channel blocker @entity72754 were tested in @entity235 cardiac Purkinje tissue. 2. Both drugs shortened action potential duration (APD). For @entity72754 (0.1-1.0 mmol/L), the reductions in APD were statistically significant at the 25% level of repolarization (APD25) for 0.1 mmol/L (P < 0.05, n = 14) and 0.5 and 1.0 mmol/L (P < 0.01, n = 6), at the 50% level of repolarization (APD50) for 0.1 mmol/L (P < 0.05, n = 14) and 0.5 and 1.0 mmol/L (P < 0.01, n = 6) and at the 90% level of repolarization (APD90) for 0.5 and 1.0 mmol/L (P < 0.01, n = 6). In contrast, @entity6335 (0.05-0.1 mmol/L) significantly shortened APD at all levels of repolarizations, with the APD50 and APD90 reduced most significantly (P < 0.01, n = 6) for higher concentrations of the drug (0.07-0.1 mmol/L). Both drugs significantly reduced the force of contraction. 3. @entity6335 (10 experiments) was more potent in suppressing @entity66783 -induced @entity943 than @entity72754 (three of seven experiments). @entity72754 reduced APD even further in the presence of @entity6335 . 4. Although @entity72754 and @entity6335 modulate different ion channels, it appears APD shortening may be a necessary, but insufficient, factor for the suppression of @entity66783 -induced @entity943 .
