Daily exercise and gender influence arterial baroreflex regulation of heart rate and nerve activity.
*Physical Conditioning; *Sex Characteristics; Animal; Animals; Arteries/*physiology; Baroreflex/*physiology; Female; Heart Rate/*physiology; Lumbosacral Region; Male; Rats; Rest; Sprague-Dawley; Sympathetic Nervous System/*physiology
The influence of daily spontaneous running (DSR) and gender on the arterial baroreflex regulation of heart rate (HR) and lumbar sympathetic nerve activity (LSNA) was examined in 13 male [7 sedentary (SED) and 6 DSR] and 12 female (6 SED and 6 DSR) Sprague-Dawley rats. After 8-9 wk of DSR or SED control, all animals were chronically instrumented with right femoral venous and left carotid arterial catheters and electrodes around the lumbar sympathetic trunk. DSR resulted in an increase in heart weight-to-body weight ratio (P = 0.001) in male and female rats and resting bradycardia in male rats (P = 0.001). Arterial baroreflex function was examined by ramp increases (1.25 +/- 0.07 mmHg/s) and decreases (1.47 mmHg/s) in arterial pressure. DSR attenuated the arterial baroreflex regulation of LSNA in a similar manner in female and male rats. DSR reduced the range (32 and 29% for female and male rats, respectively), maximum (26 and 21% for female and male rats, respectively), and maximum gain (Gmax; 46 and 17% for female and male rats, respectively). In contrast, there was a gender influence on the arterial baroreflex regulation of HR. For example, SED female rats had a higher Gmax (40%) than SED male rats. Furthermore, DSR altered the arterial baroreflex regulation of HR differently in male and female rats. DSR female rats had a reduced Gmax (38%), range (25%), and maximum (12%), whereas DSR male rats had a reduced maximum (17%) and minimum (23%). These results demonstrate that DSR attenuated the arterial baroreflex regulation of LSNA in a similar manner in female and male rats. In contrast, DSR altered the arterial baroreflex regulation of HR differently in female and male rats.
Chen C Y; DiCarlo S E
The American journal of physiology
1996
1996-11
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1152/ajpheart.1996.271.5.H1840" target="_blank" rel="noreferrer noopener">10.1152/ajpheart.1996.271.5.H1840</a>
Daily spontaneous running attenuated the central gain of the arterial baroreflex.
Animal; Animals; Arteries/*physiology; Baroreflex/*physiology; Brain/*physiology; Female; Male; Motor Activity/*physiology; Physical Conditioning; Rats; Sprague-Dawley
Exercise training attenuates arterial baroreflex function. Mechanisms responsible may include an attenuated aortic baroreceptor reactivity (afferent mechanisms) and/or an attenuated central baroreflex gain. We tested the hypothesis that the aortic baroreceptor reactivity and/or central gain is attenuated by daily spontaneous running (DSR). Eighteen anesthetized Sprague-Dawley rats (11 control and 7 DSR) were tracheotomized and instrumented with femoral venous and right carotid arterial catheters. Electrodes were placed around the left aortic depressor nerve and the lumbar sympathetic trunk. Eight to thirteen weeks of DSR were associated with a 20% increase in heart weight-to-body weight ratio (2.83 +/- 0.04 vs. 3.39 +/- 0.10 g/kg; P \textless 0.001) and resting bradycardia (413 +/- 6 vs. 384 +/- 10 beats/min; P = 0.01). DSR reduced the central gain of the baroreflex regulation of heart rate (0.210 +/- 0.046 vs. 0.005 +/- 0.021 beats.min-1.%-1; P = 0.004) during decreases in arterial pressure. However, the reactivity of aortic baroreceptor afferents and the central gain of the baroreflex control of lumbar sympathetic nerve activity were not different in control and DSR rats. Thus DSR reduced the central gain of the arterial baroreflex regulation of heart rate without changing the reactivity of aortic baroreceptor afferents. We conclude that afferent mechanisms are not responsible for the training-induced reduction in arterial baroreflex function.
Chen C Y; DiCarlo S E; Scislo T J
The American journal of physiology
1995
1995-02
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1152/ajpheart.1995.268.2.H662" target="_blank" rel="noreferrer noopener">10.1152/ajpheart.1995.268.2.H662</a>
Onset of exercise shifts operating point of arterial baroreflex to higher pressures.
*Blood Pressure; *Physical Exertion; Animals; Arteries/*physiology; Denervation; Heart Rate; Kidney/physiology; Pressoreceptors/*physiology; Rabbits; Reflex/*physiology; Sinus of Valsalva/physiology; Sympathetic Nervous System/physiology
This study was designed to test the hypothesis that the increase in sympathetic nerve activity (SNA) and mean arterial pressure (MAP) at the onset of exercise is dependent on a rapid upward shift of the operating point of the arterial baroreflex. To test this hypothesis, we recorded renal sympathetic nerve activity (RSNA) in 16 New Zealand White rabbits during treadmill running (12.6 m/min, 20% grade) under control conditions and during concomitant intravenous infusions of nitroglycerin (NTG) to attenuate the exercise pressor response. In the control condition, MAP increased 18 +/- 2 mmHg. This was associated with an increase in heart rate (HR) (104 +/- 4 beats/min) and RSNA (414 +/- 20%). The increases in RSNA (848 +/- 32%) and HR (155 +/- 5 beats/min) at the onset of exercise were significantly augmented when the rate of development of the exercise pressor response (0.3 +/- 0.03 to 0.12 +/- 0.01 mmHg/s) and the magnitudes of the pressor response (91 +/- 2 to 79 +/- 1 mmHg) were attenuated by infusions of NTG. These data suggest that at the onset of exercise the operating point of the arterial baroreflex is reset toward higher pressures. The MAP, RSNA, and HR responses to exercise were also determined in eight sinoaortic-denervated (SAD) rabbits. In the absence of a functional baroreflex, MAP (-46 +/- 2 mmHg), RSNA (-19 +/- 1%), and HR (-62 +/- 3 beats/min) decreased at the onset of exercise and recovered 1 min to -42 +/- 2, +13 +/- 1, and +9 +/- 1% of control, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
DiCarlo S E; Bishop V S
The American journal of physiology
1992
1992-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1152/ajpheart.1992.262.1.H303" target="_blank" rel="noreferrer noopener">10.1152/ajpheart.1992.262.1.H303</a>