Pharmacoresistant Cav2·3 (E-type/R-type) voltage-gated calcium channels influence heart rate dynamics and may contribute to cardiac impulse conduction

Voltage-gated Ca2+ channels regulate cardiac automaticity, rhythmicity and excitation–contraction coupling. Whereas L-type (Cav1·2, Cav1·3) and T-type (Cav3·1, Cav3·2) channels are widely accepted for their functional relevance in the heart, the role of Cav2·3 Ca2+ channels expressing R-type currents remains to be elucidated. We have investigated heart rate dynamics in control and Cav2·3-deficient mice using implantable electrocardiogram radiotelemetry and pharmacological injection experiments. Autonomic block revealed that the intrinsic heart rate does not differ between both genotypes. Systemic administration of isoproterenol resulted in a significant reduction in interbeat interval in both genotypes. It remained unaffected after administering propranolol in Cav2·3(−|−) mice. Heart rate from isolated hearts as well as atrioventricular conduction for both genotypes differed significantly. Additionally, we identified and analysed the developmental expression of two splice variants, i.e. Cav2·3c and Cav2·3e. Using patch clamp technology, R-type currents could be detected in isolated prenatal cardiomyocytes and be related to R-type Ca2+ channels. Our results indicate that on the systemic level, the pharmacologically inducible heart rate range and heart rate reserve are impaired in Cav2·3 (−|−) mice. In addition, experiments on Langendorff perfused hearts elucidate differences in basic properties between both genotypes. Thus, Cav2·3 does not only contribute to the cardiac autonomous nervous system but also to intrinsic rhythm propagation. Copyright © 2012 John Wiley & Sons, Ltd.