The effects of an extra-stimulation on post-extra-systolic potentiation in papillary muscle of rats.
The mechanism of post-extrasystolic potentiation (PESP) is unclear. It has previously been suggested that changes in both the calcium release from the sarcoplasmic reticulum (SR) and the transsarcolemmal calcium influx are factors in the development of PESP in guinea-pigs. This experiment investigated the effects of a resting interval and a coupling interval on PESP in rat papillary muscles, which have a well-developed SR. An extra-stimulation was induced at various coupling intervals and a variety of post-extrasystolic intervals were set. The PESP was not dependent on the coupling interval. The post-extrasystolic interval at which the maximal % PESP was obtained was about 90 sec, and post-extrasystolic interval-% potentiation of the PESP relationship curve consisted of an ascending limb and a descending limb. Caffeine eliminated the PESP in a concentration-dependent manner. These findings suggest that SR calcium release plays an important role in the mechanism of PESP in rats. This is consistent with results from guinea-pigs, and implies that the calcium capacity and/or retention of the SR may characterize the post-extrasystolic interval-% PESP relationship in muscle from different species.
Tatsumi
T
T
Second Department of Medicine, Kyoto Prefectural University of Medicine, Japan.
Asayama
J
J
Miyazaki
H
H
Shirayama
T
T
Omori
I
I
Inoue
D
D
Nakagawa
M
M
D000200:Action Potentials; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D005117:Cardiac Complexes, Premature / Q000378:metabolism / Q000503:physiopathology*; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
D002110:Caffeine; D002118:Calcium