title: Effects of caffeine on the mechanical properties of developing rat heart ventricles.
abstract: The effects of caffeine on isometric contractions of right-ventricular strips during the postnatal development of the rat heart were studied. Caffeine (2-10 mM) had a positive inotropic effect on ventricular strips of 3-15-days-old rats but a negative inotropic effect on the muscles of rats older than 22 days. Rest-twitch potentiation was most prominent in the muscles of 3-15-days-old rats but weakened clearly after that age. The potentiation was eliminated by 5 and 10 mM caffeine. An abrupt increase in frequency from 0.2 to 2 Hz caused a positive tension-staircase in 3-15-days-old rats but a negative staircase in older rats, the latter effect being eliminated by caffeine. It is suggested that the observed changes during the third postnatal week are due to a shift from extracellular to intracellular Ca2+ as the main source of this cation.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000375:Aging; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D005260:Female; D006321:Heart / Q000254:growth & development; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D002110:Caffeine