title: The baroreflex contribution to spontaneous heart rhythm assessed with a mathematical model in rats.
abstract: In Spontaneously Hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive rats, we quantified the extent to which spontaneous fluctuations of heart period (HP) may be determined from arterial pressure based on linear baroreflex properties. We analyzed time series (30-s length) of low-frequency (<0.8 Hz) fluctuations of HP and mean arterial pressure obtained during quiet wakefulness, rapid-eye-movement sleep (REMS) and non-rapid-eye-movement sleep (NREMS) as well as a control set of surrogate isospectral data with random phase. HP was modeled as the summed output of two parallel linear transfer functions with arterial pressure as input. The mean square difference between modeled and recorded HP was minimized by varying model parameters. The percentage of time series, in which such difference was lower than half the measured HP variance was significantly lower in REMS (6+/-1%, SHR; 5+/-1%, WKY) than either in quiet wakefulness (25+/-2%, SHR; 35+/-3%, WKY) or NREMS (33+/-3%, SHR; 27+/-3%, WKY), and in quiet wakefulness, it was significantly lower in SHR than in WKY. In surrogate data, these percentages were significantly lower than in recorded data during quiet wakefulness and NREMS, but not during REMS. The extent to which linear baroreflex properties explain spontaneous heart rhythm thus depends on the interaction between the behavioral state and the hypertensive disease, and in REMS, may be accounted for by chance couplings between HP and arterial pressure.
authors.affiliation: Department of Human and General Physiology, University of Bologna, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Berteotti
authors.forename: Carlo
authors.initials: C
authors.lastname: Franzini
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Lenzi
authors.forename: Elisa
authors.initials: E
authors.lastname: Magosso
authors.forename: Mauro
authors.initials: M
authors.lastname: Ursino
authors.forename: Giovanna
authors.initials: G
authors.lastname: Zoccoli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Silvani
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003198:Computer Simulation; D006339:Heart Rate / Q000502:physiology*; D006973:Hypertension / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012890:Sleep / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D013269:Stochastic Processes; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology*