Pharmacological modulation of vagal cardiac control measured by heart rate power spectrum: a possible bioequivalent probe.
The autonomic cardiac control was studied as a sensitive parameter of anticholinergic treatment in humans, using heart-rate (HR) power spectrum. A cross-over placebo controlled study was performed in 8 young volunteers who received increasing bolusdoses of IV atropine (from 1.3 micrograms/kg to 29.9 micrograms/kg) or placebo. Computing the HR power spectrum and integrating over specific frequency bands, we focused in particular on the respiratory frequency band (usually between 0.2-0.4 Hz) which is purely of vagal mediation. At small atropine doses (less than 5.2 micrograms/kg), the respiratory peak increased, relative to baseline, with maximal response at 2.6 micrograms/kg (from 1.0 to 1.9 +/- 0.9). Larger doses of atropine (greater than or equal to 6.5 micrograms/kg) reduced the power of the respiratory peak, by a few orders of magnitude, in a dose-dependent way. Corresponding changes were observed in mean HR but in the opposite direction i.e., a maximal bradycardia at 2.6 micrograms/kg and a nearly two fold increase in mean HR at 29.9 micrograms/kg. We conclude that atropine has a bimodal dose-dependent effect on parasympathetic cardiac control. Since the use of HR spectral analysis has been demonstrated in various animal species, we suggest that it can be used as a sensitive noninvasive probe for animal to man transformation studies.
Alcalay
M
M
Israel Defense Force-Medical Corps., Tel-Aviv.
Izraeli
S
S
Wallach-Kapon
R
R
Tochner
Z
Z
Benjamini
Y
Y
Akselrod
S
S
D000328:Adult; D001285:Atropine / Q000494:pharmacology*; D004562:Electrocardiography; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D011729:Pyridostigmine Bromide / Q000494:pharmacology; D012119:Respiration / Q000187:drug effects; D014630:Vagus Nerve / Q000502:physiology*
D001285:Atropine; D011729:Pyridostigmine Bromide