[Cardiocirculatory and respiratory reflexes of muscular origin during prolonged experimental dynamic exercise. Effects of sectioning of the sino-carotid and aortic nerves and bilateral vagotomy].

In anesthetized rabbits we have evaluated the effects of denervation of sino-aortic areas and vagotomy on the reflex cardiorespiratory responses during 2 min of contractions of gastrocnemius muscle induced by electrical stimulation of tibial nerve. The following parameters were examined: blood pressure (BP), heart rate (HR), respiratory frequency (f), tidal volume (Vt) and pulmonary ventilation (Ve) while arterial pH, pCO2 and pO2 and end-tidal CO2 (petCO2) were monitored. During steady state of rhythmic contractions we observed a decrease of BP, a slight decrease in HR and marked rise of Ve due to an increase of f with a slight increase of Vt. The sectioning of carotid-sinus, aortic and vagus nerves does not substantially modify the cardiorespiratory responses to muscular exercise; all the responses are abolished from the sectioning of somatic nerves in exercising limbs. The importance of the role of the peripheral nervous control by muscles (peripheral drive) is confirmed in the regulation of cardiorespiratory participation in motory activity, also in the steady state phase of muscular exercise in which components of a chemometabolic or hemodynamic nature could be more effective.