Abstract
1. The effects of quinidine, procaine amide and pyrilamine on the membrane resting and action potentials of ventricular muscle fibers of the guinea pig heart have been examined.
2. The mean resting potential was 52.8 mV, and the action potential 67.2 mV. The mean maximum rate of rise of the leading phase of the action potential was 121 volts/sec. The action potential duration at a stimulation rate of 240/min. was 70-100 msec.
3. No constant qualitative difference in action was observed between the three drugs. Their consistent effect was to reduce the maximum rate of rise of the actious potential. An accompanying reduction in membrane resting potential and overshoot sometimes occurred.
4. Evidence found suggests that the maximum rate of rise of the MAP may change independent of the membrane resting potential.
Footnotes
- Received February 6, 1956.
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