Cardiovascular autonomic function in conscious rats: a novel approach to facilitate stationary conditions

Dirk Ramaekers, Frank Beckers, Hilde Demeulemeester, André E Aubert, Dirk Ramaekers, Frank Beckers, Hilde Demeulemeester, André E Aubert

Abstract

Background: An experimental setting and software were developed to evaluate cardiovascular autonomic function in conscious rats. A restrained approach was used, which, upon proper habituation, induced little or no stress in the rats and limited motion artifacts.

Methods: The ECG and arterial blood pressure were recorded. Time- and frequency-domain indices of heart rate variability (HRV) and blood pressure variability (BPV) were calculated. The spontaneous baroreflex sensitivity (spBRS) was estimated using the method of statistical dependence.

Results: The power spectra clearly concentrated in a frequency band with center frequency around 0.4 Hz, the low frequency (LF) component, and one at the respiratory frequency at 1.5 Hz, the high frequency (HF) component. In baseline conditions, a direct association existed between mean R-R and especially HRV parameters denoting vagal modulation such as rMSSD, pNN5, and HF power. Beta-adrenergic blockade by propranolol diminished basal heart rate. Vagal indices increased while there was an exclusive decrease in the low frequency band of HRV. Alpha-adrenergic blockade with phentolamine produced a depressor response with tachycardia, and a clear decrease in the LF component of BPV. Both the LF and HF component in the HRV spectrum were virtually absent. Cholinergic blockade with atropine did not significantly alter BP but induced a clear tachycardia with decreased vagal indices. The HF component of HRV was completely abolished and the LF band was reduced.

Conclusions: Both alpha- and beta-adrenergic blockade left spBRS virtually unaltered, while cholinergic blockade profoundly diminished spBRS. Spectral fluctuations of beta-sympathetic tone were restricted to the LF range of HRV, while the HF respiratory component represented vagal modulation. The alpha-sympathetic system played a dominant role in the LF oscillations of BPV. A role of the vagus in the HF oscillations of BPV in the rat is questioned. The baroreflex depended mainly on changes in vagal activity.

References

    1. Ferrari AU, Daffonchio A, Albergati F, Mancia G. Inverse relationship between heart rate and blood pressure variabilities in rats. Hypertension 1997;10:33–37.
    1. Aubert AE, Ramaekers D, Beckers F, et al. Analysis of heart rate variability in unrestrained rats. Assessment of method and results. Med Biol Eng Comp 1999;60: 197–213.
    1. Meert TF, De Kock M. Interactions between the li‐pophilic opioid sufentanil and clonidine in rats after spinal application. Acta Anaesthesiologica Scandi-navica. 1996;39: 527–534.
    1. Beckers F, Ramaekers D, Aubert AE. ACTS: Automated calculation of tachograms and systograms Prog Biomed Res 1999;4: 169–165.
    1. Task Force of the European Society of Cardiology and the North American Society of pacing and electrophysiology. Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Circulation 1996;93: 1043–1065.
    1. Kreyszig E. Advanced Engineering Mathematics. J. Wiley, New York , 1979, pp. 779–783.
    1. Marple SL, Jr. Digital Spectral Analysis with Applications. Englewood Cliffs , NJ , Prentice Hall, 1987, pp. 130–165.
    1. Ramirez RW. The FFT. Fundamentals and Concepts. Englewood Cliffs , NJ , Prentice Hall, 1985, pp. 133–137.
    1. Japundzic N, Grichois ML, Zitoun P, et al. Spectral analysis of blood pressure and heart rate in conscious rats: Effects of autonomic blockers. J Auton Nerv Syst 1990: 30:91–100.
    1. Kuwahara M, Yayou K, Ishii K, et al. Power spectral analysis of heart rate variability as a new method for assessing autonomic activity in the rat. J Electrocard 1994;27:333–337.
    1. Daffonchio A, Franzelli C, Di Rienzo M, et al. Sympathetic, parasympathetic and nonautonomic contributions to cardiovascular spectral powers in unanesthetized spontaneously hypertensive rats. J Hypertens 1995;13:1636–1642.
    1. Daffonchio A, Franzelli C, Radaelli A, et al. Sympathectomy and cardiovascular spectral components in conscious nor‐motensive rats. Hypertension 1995; 25: 1287–1293.
    1. Troncoso E, Rodriguez M, Feria M. Light‐induced arousal affects simultaneously EEG and heart rate variability in the rat. Neurosci Lett 1995;188:167–170.
    1. Bendat JS, Piersol AG. Random data: Analysis and measurement procedures. Wiley‐Interscience, New York , 1971, pp. 122–125.
    1. Ducher M, Cerutti C, Gustin MP, et al. Statistical relationships between systolic blood pressure and heart rate and their functional significance in conscious rats. Med Biomed Eng Comp 1994;32:649–655.
    1. Cerutti C, Ducher M, Lantelme P, et al. Assessment of spontaneous baroreflex sensitivity in rats: A new method using the concept of statistical dependence. Amer J Physiol 1996;268:R382–388.
    1. Dawson‐Saunders B. Trapp RG. Interpreting correlation coefficients In: Basic and Clinical Biostatistics. London : Prentice‐Hall International, 1990, p. 54–56.
    1. van Vliet BN, Chafe LL, Antic V, et al. Direct and indirect methods used to study arterial blood pressure. J Pharmacol Toxicol Meth 2000;44:361–373.
    1. Mangin L, Swynghedauw B, Benis A, et al. Relationship between heart rate and heart rate variability: Study in conscious rats. J Cardiovasc Pharmacol 1998;32:601–607.
    1. Hainsworth R. Physiology of the cardiac autonomic system In Malik M. (ed): Clinical Guide to Cardiac Autonomic Tests. Kluwer, Dordrecht , 1998, pp. 3–27.
    1. Aubert AE, Ramaekers D. Neurocardiology: The benefits of irregularity. The basics of methodology, physiology and current clinical applications. Acta Cardiol 1999;54: 107–120.
    1. Massimini M, Porta A, Mariotti M, et al. Heart rate variability is encoded in the spontaneous discharge of thalamic somatosensory neurones in cat. J Physiol 2000;526:387–396.
    1. Cerutti C, Gustin M P, Paultre CZ, et al. Autonomic nervous system and cardiovascular variability in rats: A spectral analysis approach. Am J Physiol 1991;261:H292–299.
    1. Akselrod S, Eliash S, Oz O, et al. Hemodynamic regulation in SHR: Investigation by spectral analysis. Am J Physiol 1987;253:H176–183.
    1. Pomeranz B, Macaulay RJB, Caudill MA, et al. Assessment of autonomic function in humans by heart rate spectral analysis. Am J Physiol 1985;248:H151–H153.
    1. Cooke WH, Hoag JB, Grossman AA, et al. Human responses to upright tilt: A window on central autonomic integration. J Physiol 1999;517:617–628.
    1. Karemaker JM. Autonomic integration: The physiological basis of cardiovascular variability. J Physiol 1999;517:316.
    1. Aubert AE, Ramaekers D, Cuche Y, et al. Effect of long term physical training on heart rate variability. IEEE Comp Cardiol 1996;22:17–20.
    1. Murphy CA, Sloan RP, Myers MM. Pharmacological responses and spectral analysis of spontaneous fluctuations in heart rate and blood pressure in SHR rats. J Aut Nerv Syst 1991;36:237–250.
    1. Pagani M, Lombardi F, Guzzetti S, et al. Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympathovagal interactions in man and conscious dog. Circ Res 1986;59:178–193.
    1. Malliani A, Pagani M, Lombardi F, et al. Cardiovascular neuroregulation explored in the frequency domain. Research Advance Series. Circulation 1981;84: 482–492.
    1. Akselrod S, Gordon D, Saul JP, et al. Power spectrum analysis of heart rate fluctuation: A quantitative probe of beat‐to‐beat cardiovascular control. Science 1981;213:220–222.
    1. La Rovere MT, Bigger JT, Jr , Marcus F, et al. for the ATRAMI (Autonomic Tone and Reflexes after Myocardial Infarction) Investigators. Baroreflex sensitivity and heart rate variability in prediction of total cardiac mortality after myocardial infarction. Lancet 1988;351: 478–484.
    1. Sawyer R, Docherty JR. Direct cardiac actions of phenyl‐ephrine when used in assessment of baroreflex function in the rat. J Aut Pharmacol 1986;6:215–217.
    1. Pitzalis MV, Mastropasqua F, Passantino A, et al. Comparison between noninvasive indices of baroreceptor sensitivity and the phenylephrine method in postmyocardial infarction patients. Circulation 1998;97:1362–1367.

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