Expression of Ork1^{dsRNA.Scer\UAS} under the control of Scer\GAL4^NP1029, resulting in Ork1 RNAi, results in an increase of cardiac rhythm from 18% to 40% when compared to control larvae. Ork1 RNAi does not lead to arrhythmia and does not significantly affect diastoles or systoles diameter. Recording action potentials from membrane cardiomyocytes of larvae treated with Ork1 RNAi shows that the increased frequency of the automatic action potential results from a shortening of the slow diastolic depolarization phase.