Influence of atrial natriuretic factor on autonomic control of heart rate

Atrial natriuretic factor (ANF) may prevent reflex tachycardia. To determine whether this action occurs in the central or peripheral nervous system, Sprague-Dawley rats, anesthetized with Inactin (100 mg/kg ip), underwent surgical cardiac denervation and subsequent vagus nerve and stellate ganglion stimulation. We compared the change in heart rate (delta HR) in response to high- and low-frequency stimulation in a group receiving a vehicle infusion with a group receiving an ANF infusion (0.28 microgram.kg-1.min-1). We found that ANF had no effect on delta HR in the absence of all stimulation or during sympathetic stimulation at any frequency. There was no significant interaction between ANF enhancement of parasympathetic activity and the level of sympathetic stimulation. ANF acted peripherally to significantly (P less than 0.05) increase the magnitude of delta HR in response to parasympathetic stimulation at high (5 Hz) and low (2 Hz) frequencies. We speculate that a common step in mechanism of action of ANF and acetylcholine may be responsible for the enhancement of cardiac parasympathetic effects by ANF.