BACKGROUND. Heart rate follows a diurnal variation, and slow heart rhythms occur primarily at night. OBJECTIVE. The lower heart rate during sleep is assumed to be neural in origin, but here we tested whether a day-night difference in intrinsic pacemaking is involved. METHODS. In vivo and in vitro electrocardiographic recordings, vagotomy, transgenics, quantitative polymerase chain reaction, Western blotting, immunohistochemistry, patch clamp, reporter bioluminescence recordings, and chromatin immunoprecipitation were used. RESULTS. The day-night difference in the average heart rate of mice was independent of fluctuations in average locomotor activity and persisted under pharmacological, surgical, and transgenic interruption of autonomic input to the heart. Spontaneous beating rate of isolated (ie, denervated) sinus node (SN) preparations exhibited a day-night rhythm concomitant with rhythmic messenger RNA expression of ion channels including hyperpolarization activated cyclic …
D'Souza A,
Wang Y,
Anderson C,
Bucchi A,
Barsucotti M,
Olieslagers S,
Mesirca P,
Johnsen AB,
Mastitskaya S,
Ni H,
Zhang Y,
Black N,
Cox C,
Wegner S,
Bano-Otalora B,
Petit C,
Gill E,
Logantha SJ,
Dobrzynski H,
Ashton N,
Hart G,
Zhang R,
Zhang H,
Cartwright EJ,
Wisloff U,
Mangoni ME,
Da Costa Martins P,
Piggins HD,
DiFrancesco D,
Boyett MR