Author + information
- Received June 13, 1983
- Revision received September 6, 1983
- Accepted September 21, 1983
- Published online March 1, 1984.
- Robert F. Gilmour Jr., PhD, FACCa and
- Douglas P. Zipes, MD, FACC
- ↵aAddress for reprints: Robert F. Gilmour, Jr., PhD, Indiana University School of Medicine, 1100 West Michigan Street, Indianapolis, Indiana 46223.
This study determined whether acetylcholine inhibited changes in action potential duration and developed tension in canine Purkinje fibers produced by norepinephrine released during field stimulation more than it inhibited changes produced by superfusion with norepinephrine. Field stimulation increased action potential duration measured at 75% of repolarization by 9.6 ms and increased active tension by 35.5%. Acetylcholine (10-6M) almost completely inhibited changes in action potential duration and developed tension during field stimulation. Norepinephrine (10-SM to 5 x 10-8M) superfusion during normal pacing increased developed tension by 40.6%. Acetylcholine (10-6/I/) reduced this increase to 19.7%. Thus, acetylcholine inhibited the increase in tension during field stimulation by 90.7%, whereas it inhibited equivalent increases in tension produced by superfusion with norepinephrine by only 51.4% (p < 0.01).
These data suggest that acetyicholine antagonizes the effects of adrenergic stimulation by pre- and postjunctional inhibitory actions in canine cardiac Purkinje fibers.
This study was supported in part by the Herman C. Krannert Fund, Indianapolis, Indiana, by Grants HL-06308 and HL-07182 from the National Heart, Lung, and Blood Institute of the National Institutes of Health, Bethesda, Maryland, and by the Attorney General of Indiana Public Health Trust, the Roudebush Veterans Administration Medical Center, Indianapolis, Indiana and a Grant-In-Aid from the American Heart Association, Indiana Affiliate, Inc., Indianapolis, Indiana.
- Received June 13, 1983.
- Revision received September 6, 1983.
- Accepted September 21, 1983.
- American College of Cardiology Foundation