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  • 1
    Electronic Resource
    Electronic Resource
    ARTERIAL BAROREFLEX CONTROL OF HEART PERIOD IS NOT RELATED TO BLOOD PRESSURE VARIABILITY IN CONSCIOUS HYPERTENSIVE AND NORMOTENSIVE RATS (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 19 (1992), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The short-term (within 30 min periods) and the long-term (among 30 min periods) variabilities, expressed as variation coefficients, of blood pressure (BP) and heart period (HP) were studied using a computer analysis of BP recordings in freely moving genetically hypertensive (LH), normotensive (LN) and low BP (LL) rats of Lyon strains at ages 5, 9, 21 and 40 weeks. The baroreflex control of HP was estimated with the slope of the linear relationship between systolic BP (SBP) and HP (SBP-HP slope) computed after phenylephrine and nitroglycerin injections.2. Short-term variability of BP increased between 5 and 9 weeks of age and then remained stable. Hypertension was accompanied by an increase in both short-and long-term variabilities of diastolic BP in adult rats.3. A sharp increase in SBP-HP slope was observed between 5 and 9 weeks of age in LN rats. SBP-HP slope of LH rats increased slightly up to 21 weeks but remained lower than that of normotensive controls.4. The weak inverse correlation existing between SBP-HP slope and BP variability appeared to be mediated by the BP level. In addition, atropine which is known to abolish almost completely the SBP-HP slope, did not increase BP variability. It is concluded that SBP-HP slope is not linearly associated with BP variability in conscious rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1992.tb00414.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect Of α-Adrenoceptor Blockade On The 0.4 Hz Sympathetic Rhythm In Conscious Rats (2001)
    Melbourne, Australia : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 28 (2001), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The present study examined the origin of the 0.4 Hz rhythm in renal sympathetic nerve activity (RSNA) in rats. It was anticipated that, after elimination of 0.4 Hz oscillations of arterial pressure (AP) by α-adrenoceptor blockade, the persistence or disappearance of a 0.4 Hz rhythm in RSNA would point to an endogenous (central oscillator) or baroreflex origin, respectively.2. Arterial pressure and RSNA were recorded in seven conscious rats, before and after acute α-adrenoceptor blockade with phentolamine (5 mg/kg, i.v.). In each condition, power and coherence spectra were calculated over 15 min periods of rest.3. In control conditions, highly coherent AP and RSNA oscillations were observed near 0.4 Hz. After phentolamine administration, spectral power in the mid-frequency (0.27–0.74 Hz) band was significantly reduced for both AP and RSNA and maximum power was shifted towards 0.7 Hz.4. The disappearance of the RSNA rhythm at 0.4 Hz after phentolamine administration favours the hypothesis of a baroreflex origin. The new oscillation near 0.7 Hz can derive either from the activity of a previously unrecognized central oscillator or from a faster feedback mechanism involving cotransmitters of noradrenaline acting with shorter time constants (e.g. ATP).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1681.2001.03561.x
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  • 3
    Electronic Resource
    Electronic Resource
    CHARACTERIZATION OF A MAJOR SLOW OSCILLATION IN THE MESENTERIC CIRCULATION OF CONSCIOUS RATS (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 25 (1998), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Little is known about spontaneous slow rhythms in regional circulations. The present study was aimed at characterizing low-frequency (LF; 78–269 mHz) oscillations in the mesenteric and hindquarter circulations of conscious rats.2. Mean arterial pressure (MAP) and indices (pulsed Doppler technique) of mesenteric (n= 25) and hindquarter (n= 23) blood flows were recorded in conscious, freely moving rats during 1 h periods. Fast Fourier transform analysis was applied to beat-to-beat data after resampling at 10 Hz of consecutive 205 s time series.3. A major oscillation centred at 164±4mHz was present in the mesenteric, but not in hindquarter, circulation. Consequently, LF power accounted for approximately 43% of the overall variability of mesenteric blood flow. Cross-spectral analysis performed between MAP and mesenteric blood flow indicated that fractional changes in flow were approximately two-fold of those in MAP, in pressure, at the peak frequency.4. Acute blockade of the autonomic, renin-angiotensin and vasopressin systems combined with noradrenaline infusion (n= 7) reduced the frequency of the mesenteric blood flow oscillation (115 ± 6 mHz) but did not change its contribution to overall flow variability (approximately 48%). A clear oscillation was still present after acute inhibition of nitric oxide (NO) synthesis with NG-nitro-l-arginine methyl ester (n= 8), but was virtually absent in chronically guanethidine-sympathectomized rats (n= 12).5. In conclusion, the mesenteric blood flow of conscious rats exhibits a major slow oscillation that originates in the mesenteric vasculature and is not secondary to the activity of the major pressor systems or to the cyclic release of NO. Because of the strong attenuation of the oscillation in sympathectomized rats, we suggest that adrenergic vasoconstrictor tone plays a permissive role in its genesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1998.tb02160.x
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  • 4
    Electronic Resource
    Electronic Resource
    CARDIOVASCULAR HABITUATION TO EMOTIONAL STRESS IN LYON HYPERTENSIVE RATS (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 19 (1992), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Intra-aortic blood pressure was recorded continuously in freely moving genetically hypertensive (LH), normotensive (LN) and low blood pressure (LL) rats of the Lyon strain during two 11 h periods (08:00-19:00 h). During the first period (control), the animals were left undisturbed and during the second period (stress), a jet of air was applied for 20 min every hour. Urine was collected simultaneously and analysed for its content in norepinephrine and epinephrine.2. The first exposure to the stressor induced larger increases in blood pressure and heart rate in LH than in LN and LL rats. However blood pressure and heart rate responses to the 10 following stressors decreased in LH rats while they remained stable in LN and LL animals.3. Repeated stress exposure induced significant increases in epinephrine excretion in both LN and LL but not in LH rats.4. It is concluded that LH rats exhibit marked cardiovascular habituation to repeated stress. Taken together with the lack of stress-induced sympathoadrenal activation, this suggests a reduced level of emotional responsiveness in Lyon hypertensive rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1992.tb00437.x
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  • 5
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    Unknown
    COMMENTARY (1972)
    New York, N.Y. : Periodicals Archive Online (PAO)
    Harper's. 244:1464 (1972:May) 94 
    Details
    ISSN: 0017-789X
    Topics: General, Interdisciplinary
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5128-1972-244-64-000006
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