Effect of brief ultrasound exposure on post-tetanic potentiation in cardiac muscle.
The effect of a short 4 second ultrasound application (1.0 W/cm2 sATA at 963 KHz) on the post-tetanic-potentiation of isolated isometrically contracting rat papillary muscle has been evaluated. Post tetanic-potentiation was produced in hypoxic isolated papillary muscle by interrupting the control stimulation rate of 6/minute with 10 stimulating pulses at 0.2 sec intervals for one cycle. Ultrasound application varied from one second prior to the stimulating train to a period covering the entire train. Ultrasound application just preceding and impinging upon the pulse train, enhanced post-tetanic-potentiation contractions. However, delay in ultrasound application and covering the stimulating pulse train, reduced post-tetanic-potentiation contractions. These data suggest that a window exists for the effects of ultrasound on contracting myocardium which may be used to probe critical events in the cardiac cycle.
D000818:Animals; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D009200:Myocardial Contraction; D010210:Papillary Muscles / Q000502:physiology*; D010812:Physical Stimulation; D051381:Rats; D013997:Time Factors; D014465:Ultrasonics