Pevtsova E I, Samonina G E, Sokolova N A, Udel'nov M G
Fiziol Zh SSSR Im I M Sechenova. 1980 Jul;66(7):1093-1100.
Chronotropic effects on the cod heart in case of the parasympathetic stimulation alone were initially negative and rather small; the joint stimulation of parasympathetic and sympathetic nerves or the vagus stimulation after noradrenaline administration augmented the initial bradycardia. In case of initial marked parasympathetic negative chronotropic effect, catecholamines diminished the parasympathetic inhibition. The sympathetic innervation and its transmitter seem to be able to increase the cholinergic effect.