Cardiac afferents attenuate the muscle metaboreflex in the rat
| Autor: | S. E. DiCarlo, H. L. Collins |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Mean arterial pressure
Baroreceptor Physiology Efferent Physical Exertion Scopolamine Derivatives Hemodynamics Blood volume Blood Pressure Procainamide Specimen Handling Heart Rate Physiology (medical) medicine.artery Reflex medicine Animals Neurons Afferent Aorta Blood Volume business.industry Muscles Parasympatholytics Heart N-Methylscopolamine Propranolol Rats Blood pressure Anesthesia Circulatory system cardiovascular system business |
| Zdroj: | Journal of applied physiology (Bethesda, Md. : 1985). 75(1) |
| ISSN: | 8750-7587 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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