Objective:To explore electrophysiological characteristics of cardiomyocytes at different developmental stages from C57 mice by microelectrodes arrays.Methods: The single ventricular cardiomyocytes from fetal in 13.5~19.5 d and neonatal in 2 d C57 mice were obtained and cultured in MEA(microelectrode arrays)plates about 48 h respectively

and to be observed through the methods of inverted phase contrast microscope

transmission electron microscope

scanning electron microscope

and identified through immunocytochemistry and MEA which investigated the electrophysiological properties.ECGs and heart rate variability(HRV)were recorded in conscious

unsedated C57 mice at different postnatal days(days 1

7

14

21

28

35

>60).Results: The field potential duration prolonged with the increase of gestational age in cultured ventricular cardiomyocytes(P<0.01)

then decreased in neonatal(P<0.01).And the beat frequence decreased with development in ventricular cardiomyocytes from embryotal mice.In postnatal mice

the heart rhythm was sinus rhythm

mean PR

RR

QRS

QT

JT interval decreased with development

there was significant difference on day 1 and day 7(P< 0.01)

and without significant difference on day 14

21

28

35 and > 60.The J-S-T segment was elevated in day 1 neonatal

resolved by day 14 and disappeared in 35 day.The HRV increased with development.Conclusion:The field potential properties of embryonic cardiomyocytes and ECG intervals and morphological changes during the normal postnatal mice with development may provide some useful information for exploration the development of electrophysiology characteristics in heart from C57 mice.