Table 1.

Linear effects of vagal stimulation on heart period across species and conditions

Study	Species				Baseline IBI	Effect of right cardiac vagus stimulation on IBI (ms/Hz)	Vagal effect on IBI as % of baseline IBI
							Study specific	Average for species
Carlson et al., 1992	Human				740	75	10.1%	10.1%
Furukawa et al., 1990	Dog				520	24.2	4.7%
Levy & Zieske, 1969a	Dog				395	42	10.6%
Levy & Zieske, 1969b	Dog				456	47.4	10.4%
Parker et al., 1984	Dog				258	38	14.7%
Randall et al., 2003	Dog				508	86.6	17.0%
Stramba‐badiale et al., 1991	Dog				500	33.2	6.6%
Urthaler et al., 1986	Dog				408	16.2	4.0%	11.4%
Berntson et al., 1992	Rat				240	7.4	3.1%	3.1%
de Neef et al., 1983	Rabbit				208	17.9	8.6%
Ford & McWilliam, 1986	Rabbit				225	14.6	6.5%
Shimizu et al., 2009	Rabbit				205	12.5	6.1%	7.5%
de Neef et al., 1983	Cat				256	27.8	10.9%	10.9%
de Neef et al., 1983	Guinea pig				218	26.5	12.2%	12.2%
These experiments repeated vagal stimulation without and with concurrent stimulation of the cardiac sympathetic nerve at 4 Hz:
Levy & Zieske, 1969a		Mongrel dogs		without	395	42	10.6%
Levy & Zieske, 1969a		Mongrel dogs		with	284	39.2	13.8%
Randall et al., 2003		Mongrel dogs		without	508	86.6	17.0%
Randall et al., 2003		Mongrel dogs		with	316	42.2	13.4%
Urthaler et al., 1986		Beagle puppies		without	408	16.2	4.0%
Urthaler et al., 1986		Beagle puppies		with	317	15.8	5.0%
This experiment repeated vagal stimulation with the dogs standing quietly at the treadmill or forced to run until a heart rate of 200 bpm was reached:
Stramba‐Badiale et al., 1991		Dog		Standing quiet	500	33.2	6.6%
Stramba‐Badiale et al., 1991		Dog		Running (200 bpm)	299	28.8	9.6%

Upper half of the table depicts results of studies that use vagal stimulation to decrease heart period from its baseline level achieved at compete autonomic denervation The (mostly right) vagal nerve was stimulated at various frequencies, and the increases in heart period from a baseline heart period are regressed on the vagal firing frequency to obtain the slope, which can be expressed in absolute units (ms/Hz) or as a percentage of the basal heart period. Lower half of the table depicts results of studies that repeated vagal stimulation at different levels of baseline heart period level, which were induced by sympathetic stimulation or exercise. IBI = interbeat interval.