The nervous control of cardiac output

The nervous control of the cardiac output was studied in the anesthetized and hemithoracotomized dogs. 1) The stimulation of the left sympathetic cardiac nerve usually caused biphasic increase in cardiac output as well as biphasic elevation of the systemic blood pressure. Initial marked increase in cardiac output was accompanied with the first elevation of blood pressure during the stimulation. After the stimulation, however, the late elevation of blood pressure was usually accompanied with only a slight increase in cardiac output and marked increase in coronary blood flow. 2) The stimulation of the right sympathetic cardiac nerve caused marked tachycardia with less increase in cardiac output compared with these changes on the left side. 3) The stimulation of the proximal end of the cut cervical vagal nerve caused pressor and/or depressor effect. In the pressor response, cardiac output increased slightly almost in parallel with the systemic blood pressure, while in the depressor response, cardiac output increased with the depression of the blood pressure. 4) The carotid sinus nerves influence particularly the biphasic elevation of the blood pressure by stimulation of the left sympathetic cardiac nerve. 5) The changes of the coronary blood flow were parallel with the blood pressure than with the cardiac output.