Zh Evol Biokhim Fiziol. 1975 Mar-Apr;11(2):159-63.
Zhurnal evoliutsionnoi biokhimii i fiziologii
[Article in Russian] N S Akopyan
PMID: 1217289
Newborn dogs and rabbits exhibit unequal reactivity of cardiac activity to acute hypoxia as compared to adult ones, being lesser in the newborn. In dogs, during postnatal life as well as during adaptation to hypoxia, tachycardic effect of atropine increases indicating the increase in vagal tone. In growing rabbits, cardiac rhythm decreases, the decrease being presumably due to changes in the tone of the sympathetic nervous system, since no significant changes were observed in cardiac activity during atropine administration.