The participation of arterial baroreceptor reflexes in the prolonged inhibition of the electrical activity of the sympathetic nerves

: In immobilised male cats, arterial and venous pressure, heart rate and electrical activity of the renal nerve were recorded during i.v. infusion of noradrenaline at a constant initial level of arterial and venous pressure. The electrical activity of the renal nerve was inhibited and the heart rate decelerated, the obviousness of these effects increasing with acceleration of the infusion rate. The bradycardia was transient in anesthesia. The section of both vago-sympathetic trunks prevented the bradycardia and weakened the inhibition of the renal nerve activity. Additional denervation of both carotid sinuses eliminated the inhibiting effect of noradrenaline. Possible mechanisms of the noradrenaline effects are discussed.