Cardiac dynamics in corticotropin-releasing factor receptor subtype-2 deficient mice

The action of corticotropin-releasing factor (CRF) is mediated by two recently identified receptors, CRFR1 and CRFR2, that differ with respect to their anatomical distribution and pharmacologic ligand-binding properties. Here we show by an analysis of circadian heartbeat interval fluctuations that CRFR2-deficiency in mice does not interfere with the dynamical mechanisms underlying the control of heart rate. Hence, intact CRFR2 would not constitute an indispensable requirement of physiologic cardiac rhythm regulation. However, both CRFR2 knockout (-/-) and wildtype control (+/+) mice showed altered dynamical properties of cardiac interbeat fluctuations in contrast to homogenetic inbred strains of mice (C57BL/6N and C57BL/6J). The results stress the impact of genetic background and support the generalized notion that transgenic 129/Sv-derived knockout mice exhibit altered cardiac dynamics which is interpreted to reflect an attenuation of neuroautonomic sympatho-vagal antagonism.