Autonomic modulation of ultradian blood pressure and heart rate oscillations in dogs.
Autonomic receptor modulation of ultradian oscillations of blood pressure and heart rate was studied in telemetered free-running dogs. Data, analyzed for their harmonic content by fast Fourier transform (FFT) methods, indicated that ultradian and circadian oscillations of 22.9 +/- 2.5 and 10.5 +/- 0.9 (SD) mmHg, respectively, were present. The average principal frequency for the ultradian oscillations in 12 dogs was 0.760 +/- 0.11 cycles/h for arterial pressure and 0.808 +/- 0.10 for heart rate. Atropine had no effect on periodicity of either arterial pressure or heart rate. Metoprolol, a beta 1-antagonist, or hexamethonium, a ganglionic blocker, significantly reduced the power of both arterial pressure and heart rate (P less than 0.05), whereas the primary frequencies of both were unchanged. Prazosin, an alpha 1-blocker, sharply reduced arterial pressure power (P less than 0.05) and increased the power of heart rate (P less than 0.05), demonstrating that it is possible to uncouple arterial pressure oscillations from influences of heart rate. We conclude that the sympathetic limb of the autonomic nervous system is primarily responsible for these oscillations and that vagal influences on the heart partially dampen these rhythms.
Broten
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TP
Department of Physiology and Biophysics, University of Illinois, Urbana 61801.
Zehr
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JE
D000204:Activity Cycles; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002940:Circadian Rhythm; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000502:physiology; D011224:Prazosin / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology
D006584:Hexamethonium Compounds; D018738:Hexamethonium; D008790:Metoprolol; D011224:Prazosin