Karmanova I G, Belich A I, Shilling N V
Zh Evol Biokhim Fiziol. 1983 May-Jun;19(3):282-8.
Computer treatment of the continuous row of R-R intervals of the ECG revealed the general pattern and masked periodicity of the diurnal dynamics of the heart rate in the frog Rana temporaria. It was found that in day time intact frogs exhibit tonic decrease of the heart rate with a maximum at about 12 a.m. At night, there is a tendency to tachycardia with a maximum at about 4 a.m. This periodicity of the heart rate is monitored mainly by the anterior and posterior hypothalamus.
