Acute exercise and gender alter cardiac autonomic tonus differently in hypertensive and normotensive rats.
*Sex Characteristics; Adrenergic alpha-Antagonists/pharmacology; Animals; Autonomic Nervous System/drug effects/*physiopathology; Blood Pressure; Female; Heart Rate/physiology; Heart/*innervation; Hypertension/*physiopathology; Inbred SHR; Inbred WKY; Male; Metoprolol/pharmacology; N-Methylscopolamine/pharmacology; Parasympathetic Nervous System/drug effects/physiopathology; Parasympatholytics/pharmacology; Physical Exertion/*physiology; Rats; Sympathetic Nervous System/drug effects/physiopathology
Arterial pressure (AP), heart rate (HR), cardiac sympathetic tonus (ST), and parasympathetic tonus (PT) were determined in spontaneously hypertensive rats (SHR, 8 male and 8 female) and Wistar-Kyoto normotensive rats (WKY, 8 male and 12 female) before and after acute exercise. Before exercise, hypertensive rats (regardless of gender) had an increased ST (+15 beats/min), increased resting HR (+12 beats/min), and decreased PT (-11 beats/min). Similarly, female rats (regardless of strain) also had an increased ST (+15 beats/min), increased resting HR (+39 beats/min), and decreased PT (-14 beats/min). Hypertensive rats had a significant reduction in AP (-17 +/- 3 mmHg), ST (-26 beats/min), PT (-7 beats/min), and HR (-14 beats/min) after exercise. In contrast, AP was not reduced in normotensive rats and ST (+18 beats/min) and HR (+42 beats/min) were increased in female normotensive rats after exercise. However, male normotensive rats had a postexercise reduction in ST (-14 beats/min) and HR (-19 beats/min). In summary, AP, ST, and resting HR were higher whereas PT was lower in hypertensive vs. normotensive rats. Furthermore, females had a higher resting HR, intrinsic HR, and ST and lower PT than male rats. These data demonstrate that gender and the resting level of AP influence cardiac autonomic regulation.
Chandler M P; DiCarlo S E
The American journal of physiology
1998
1998-02
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/ajpregu.1998.274.2.r510" target="_blank" rel="noreferrer noopener">10.1152/ajpregu.1998.274.2.r510</a>
Cardiac afferents attenuate the muscle metaboreflex in the rat.
Afferent/drug effects/*physiology; Animals; Aorta/drug effects/physiology; Blood Pressure/drug effects/physiology; Blood Volume/drug effects/physiology; Heart Rate/drug effects/physiology; Heart/drug effects/*innervation/physiology; Muscles/drug effects/*metabolism; N-Methylscopolamine; Neurons; Parasympatholytics/pharmacology; Physical Exertion/physiology; Procainamide/pharmacology; Propranolol/pharmacology; Rats; Reflex/drug effects/*physiology; Scopolamine Derivatives/pharmacology; Specimen Handling
The influence of cardiac afferents on the muscle metaboreflex was examined in 16 rats instrumented with a Silastic-tipped catheter in the pericardial space and right atrium, Doppler ultrasonic flow probe and a pneumatic vascular occluder around the terminal aorta, and a Teflon catheter in the thoracic aorta. In protocol I (cardiac efferent and afferent blockade), the muscle metaboreflex was examined under three experimental conditions: 1) control, 2) cardiac autonomic efferent blockade [intrapericardial methylscopolamine (10 micrograms/kg) and propranolol (50 micrograms/kg)], and 3) combined cardiac autonomic efferent and afferent blockade (intrapericardial procainamide, 2%). In protocol II (blood volume expansion), the muscle metaboreflex was examined before and after 15% blood volume expansion. Mild treadmill exercise (9 m/min, 10% grade) increased heart rate (71 +/- 9.4 beats/min), mean arterial pressure (12 +/- 2.0 mmHg), and terminal aortic blood flow velocity (6 +/- 1.0 kHz). During exercise, a reduction of terminal aortic blood flow velocity (10.5 +/- 1.1%) reduced mixed venous PO2 18 +/- 6%. The gain of the muscle metaboreflex in the control condition was 14.6 +/- 2.9 mmHg/kHz. Efferent blockade reduced the gain 51 +/- 7%. However, combined cardiac efferent and afferent blockade increased the gain 207 +/- 64% above the efferent blocked condition and restored the gain to levels above those obtained in the control condition (18.3 +/- 4.6 mmHg/kHz). In addition, 15% blood volume expansion reduced the gain of the muscle metaboreflex regulation of mean arterial pressure and heart rate (44 +/- 9.5% and 41 +/- 12.0%, respectively). Thus cardiac afferents tonically inhibit the pressor response to a reduction in terminal aortic blood flow velocity during exercise.
Collins H L; DiCarlo S E
Journal of applied physiology (Bethesda, Md. : 1985)
1993
1993-07
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/jappl.1993.75.1.114" target="_blank" rel="noreferrer noopener">10.1152/jappl.1993.75.1.114</a>