<prompt> Vagal stimulation of the hea causesIncreased hea rateIncreased R-R interval in ECGIncreased force of hea contractionIncreased cardiac output  <response>: The right and left vagus nerves in the neck region were exposed by dissection, and bipolar, multiturn, helical, silicone leads were wrapped around the vagus nerves. Stimulation was applied by an external device with multivariable settings: frequency 10-100 Hz, pulse duration 100-700 usec; delay 0-0.5 msec; current 0.5-14 mA. Measurements were performed under normal sinus rhythm RR-interval 501 - 30 msec and during isoprenaline-induced tachycardia RR-interval 284 - 11 msec. Results. VNS, under optimal pacing conditions 100 Hz; 5 mA; 0.2 msec; 70 msec delay, in an electrocardiogram-triggered ECG-triggered pacing mode, increased RR-intervals by approximately 40, irrespective of the duration of the RR-interval preceding VNS. 