title: Autonomic function and baroreflex sensitivity during a normal ovulatory cycle in humans.
abstract: OBJECTIVE
  Possible variations occurring in the autonomic function during a normal ovulatory cycle have been poorly investigated and it is not known whether the baroreflex sensitivity may change according to the different phases of the cycle. The aim of this study was to evaluate heart rate variability (power spectrum analysis), and baroreceptor sensitivity (alpha-low frequency coefficient) in 13 young women with regular menses during the two phases of the cycle (phase I: 5 +/- 1 days and phase II: 23 +/- 3 days from bleeding).
  
  
  RESULTS
  The low frequency/high frequency ratio was significantly higher in the second phase of the cycle (phase I: 2.8 +/- 2.6; phase II: 5.6 +/- 5.8, p < 0.05), in the presence of increased low frequency and reduced high frequency expressed in normalized units-nu-(phase I: 59.8 +/- 16.7 nu and 32.6 +/- 15.6 nu for low frequency and high frequency, respectively; phase II: 67.7 +/- 18 nu and 25.7 +/- 17.5 nu for low frequency and high frequency, respectively; p < 0.05). The alpha-low frequency coefficient, index of baroreflex sensitivity, did not statistically differ in the two phases (phase I: 10.6 +/- 4.5 msec/mm Hg; phase II: 8.9 +/- 4.9 msec/mm Hg; ns).
  
  
  CONCLUSIONS
  The power spectrum analysis suggests that the autonomic function may be affected by the ovulatory cycle, sympathetic activation being relatively increased in the second phase. On the contrary, the baroreceptor function seems to be scarcely influenced by the two phases of the menstrual cycle.
authors.affiliation: Chair of Internal Medicine, University of Insubria, Varese, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Guasti
authors.forename: P
authors.initials: P
authors.lastname: Grimoldi
authors.forename: L T
authors.initials: LT
authors.lastname: Mainardi
authors.forename: M R
authors.initials: MR
authors.lastname: Petrozzino
authors.forename: E
authors.initials: E
authors.lastname: Piantanida
authors.forename: D
authors.initials: D
authors.lastname: Garganico
authors.forename: A
authors.initials: A
authors.lastname: Diolisi
authors.forename: D
authors.initials: D
authors.lastname: Zanotta
authors.forename: A
authors.initials: A
authors.lastname: Bertolini
authors.forename: W
authors.initials: W
authors.lastname: Ageno
authors.forename: A M
authors.initials: AM
authors.lastname: Grandi
authors.forename: S
authors.initials: S
authors.lastname: Cerutti
authors.forename: A
authors.initials: A
authors.lastname: Venco
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D010060:Ovulation / Q000502:physiology*