[Mechanisms of tachycardia caused by administration of atropine and vagotomy in animals of various species].

Acute experiments on pigeons, rabbits, rats, and guinea pigs demonstrated that the cause of vagotomic tachycardia is exclusion of inhibitory tone of the vagus nerve rather than excitation of the sympathico-adrenal system. With cholinergic neurons, the vagus nerve may accelerate or slow down cardiac rhythm only in animals with marked tone. In its absence, there may be only inhibitory effects, but short-term stimulation is evident, postvagal tachycardia results from cessation of inhibitory effects.