title: Autonomic and ventilatory components of heart rate and blood pressure variability in freely behaving rats.
abstract: The relative role of parasympathetic, sympathetic, and ventilatory influences in the genesis of blood pressure and R-R interval variability is controversial. In 13 freely behaving WKY rats instrumented with venous and arterial catheters and chest electrodes, mean arterial pressure (MAP, mmHg), R-R interval (ms), and respiratory fluctuations were monitored for 90 min in the control condition and after intravenous atropine (0.75 mg/kg) and/or propranolol (1 mg/kg). Spectral power (pw) in the 0.25- to 0.75-Hz (midfrequency, MF) and the 0.75- to 3.0-Hz (high-frequency, HF, respiratory-synchronous) bands was computed in sequences of 400 heartbeats by use of a combined autoregressive analysis. Atropine reduced but did not abolish HF R-R interval pw (from 1.73 +/- 0.50 to 0.39 +/- 0.27 ms2, P < 0.01) and halved HF MAP pw (from 0.41 +/- 0.30 to 0.21 +/- 0.12 mmHg2, P < 0.05), whereas propranolol did not affect HF pw of the R-R interval or MAP. Propranolol also failed to significantly modify MF R-R interval pw (from 0.48 +/- 0.44 to 0.40 +/- 0.34 ms2, P = NS) or MF MAP pw (from 0.54 +/- 0.39 to 0.42 +/- 0.20 mmHg2, P = NS), whereas atropine virtually abolished MF R-R interval pw (from 0.48 +/- 0.44 to 0.01 +/- 0.01 ms2, P < 0.01) and also significantly reduced MF MAP pw (from 0.54 +/- 0.39 to 0.33 +/- 0.24 mmHg2, P < 0.01). The effects of combined blockade were similar to those of atropine alone.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Centro Fisiologia Clinica ed Ipertensione, Università di Milano, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Perlini
authors.forename: F
authors.initials: F
authors.lastname: Giangregorio
authors.forename: M
authors.initials: M
authors.lastname: Coco
authors.forename: A
authors.initials: A
authors.lastname: Radaelli
authors.forename: P L
authors.initials: PL
authors.lastname: Soldà
authors.forename: L
authors.initials: L
authors.lastname: Bernardi
authors.forename: A U
authors.initials: AU
authors.lastname: Ferrari
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001340:Autonomic Nerve Block; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D012119:Respiration / Q000502:physiology*
chemical_list: D001285:Atropine; D011433:Propranolol