Key result
R(-)-efonidipine significantly decreased the beating rate in mouse and guinea pig right atria but not in rabbit atria, demonstrating species differences in the contribution of T-type Ca2+ currents to cardiac pacemaking.
Why the study?
Does R(-)-efonidipine reduce beating rate and prolong pacemaker depolarization in isolated right atrial tissue from mice, guinea pigs, and rabbits?
Does R(-)-efonidipine reduce beating rate and prolong pacemaker depolarization in isolated right atrial tissue from mice, guinea pigs, and rabbits?
Absolute Event Rate: 380% vs 408%
p-value: p=<0.05
The contribution of T-type Ca2+ current to cardiac pacemaking differs among species, being prominent in mice, small in guinea pigs, and absent in rabbits.
Species differences limit translation to human pacemaking; leaves open T-type Ca2+ current contributions in clinical models.
The contribution of the T-type Ca2+ current to cardiac pacemaking was examined in isolated right atrial tissue from the mouse, guinea pig, and rabbit using a specific blocker, R(-)-efonidipine. At 10(-6) M, R(-)-efonidipine produced negative chronotropy, which was prominent in the mouse and small but significant in the guinea pig. No effect was observed in the rabbit. Microelectrode recordings revealed that R(-)-efonidipine significantly prolongs the pacemaker (phase 4) depolarization of the sinoatrial-node action potential in the mouse and guinea pig. These results provide the first pharmacological evidence that the contribution of T-type Ca2+ current to cardiac pacemaking differs among experimental animal species.
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Tanaka et al. (2008) studied Cardiac pacemaking (animal model). R(-)-efonidipine vs. Baseline (before application) was evaluated on Beating rate (beats/min) in isolated mouse right atria (p=<0.05). R(-)-efonidipine significantly decreased the beating rate in mouse and guinea pig right atria but not in rabbit atria, demonstrating species differences in the contribution of T-type Ca2+ currents to cardiac pacemaking.
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