title: Laterality in direct and indirect inotropic effects of sympathetic stimulation in isolated canine heart.
abstract: Although sympathetic nerve stimulation is known to increase ventricular contractility, concomitant increases in heart rate (HR) make it difficult to separate its direct inotropic effect from indirect inotropic effect through a force-frequency mechanism. We stimulated the stellate ganglia in 8 isolated canine hearts with functional sympathetic nerves. Right sympathetic stimulation at 10 Hz increased ventricular end-systolic elastance (E(es)) by 95.7 +/- 7.5% (p < 0.001) and HR by 32.5 +/- 4.2% (p < 0.05). In contrast, left sympathetic stimulation at 10 Hz increased E(es) by 70.7 +/- 6.5% (p < 0.001) without significant changes in HR. Preventing the chronotropic response by fixed-rate pacing attenuated the E(es) response to right sympathetic stimulation at 5 Hz (52.0 +/- 5.1 vs. 22.8 +/- 2.8%, p < 0.001), but not to left sympathetic stimulation at 5 Hz (54.5 +/- 3.4 vs. 53.3 +/- 2.2%, NS). In the isolated canine heart, the right sympathetic nerve affected E(es) by both the direct inotropic effect and the indirect HR-dependent inotropic effect. In contrast, the left sympathetic nerve regulated E(es) primarily by its direct inotropic effect.
authors.affiliation: Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Suita, 565-8565 Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakayama
authors.forename: H
authors.initials: H
authors.lastname: Miyano
authors.forename: T
authors.initials: T
authors.lastname: Shishido
authors.forename: M
authors.initials: M
authors.lastname: Inagaki
authors.forename: T
authors.initials: T
authors.lastname: Kawada
authors.forename: M
authors.initials: M
authors.lastname: Sugimachi
authors.forename: K
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004285:Dogs; D005260:Female; D006321:Heart / Q000294:innervation / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D013233:Stellate Ganglion / Q000502:physiology*