Abstract Background Voltage dependent Ca channels are divided to L-, T-, N-, P/Q-, and R-types, and N-type Ca channel (NCC) is mainly expressed in nerve terminal and regulates neurotransmitter release. Recently, NCC has been reported to express in adrenal gland and renal tubular cells. We examined whether NCC is expressed in cardiac myocytes and if so, the roles of this channel. Methods Expression of NCC mRNA and protein in cardiomyocytes were assessed by quantitative real time PCR and Western blot analysis using neonatal rat cultured cardiomyocytes, infant, and adult rat hearts. Expression site of NCC in cardiomyocytes was examined by confocal imaging of immunofluorescent staining. The roles of NCC in physiological Ca transient in neonatal myocytes were examined using fluorescence imaging of Fluo4, an intracellular Ca indicator. To examine the effects of pathological condition, such as heart failure and ischemia-reperfusion, on NCC expression, cultured cardiomyocytes were treated with norepinephrine (10 μmol/L, 24 hours) or subjected to 5 hours of hypoxia followed by 30 minutes of reoxygenation. In addition, adult rats were subjected to myocardial infarction by ligating the left anterior coronary artery. Lethal myocyte injury was examined by LDH activity in culture medium and myocyte apoptosis was examined by nuclear staining with DAPI and caspase 3 activity. To clarify the roles of NCC in neonatal myocytes in these pathological conditions, we examine the effect of ω-conotoxin, a selective NCC blocker. Results NCC mRNA and protein were expressed in neonatal cardiomyocytes. Immunocytochemical staining showed NCC was expressed in myocyte plasma membrane. During physiological spontaneous beating, ω-conotoxin did not affect beating rate and intra cellular Ca transient, suggesting that the roles of NCC on physiological beating are little. After birth level of NCC mRNA expression in cardiac tissue gradually decreased within 2 weeks and low level of mRNA expressed continuously in adult cardiac tissue. However, in pathological condition, mRNA and protein levels of NCC in non-infarcted region were increased 4 weeks after myocardial infarction. In addition, hypoxia-reoxygenation and norepinephrine administration increased LDH release and myocyte apoptosis in association with increase in NCC expression in neonatal cultured myocytes. ω-conotoxin significantly suppressed hypoxia/reoxygenation- and norepinephrine-induced LDH release and caspase 3 activation. Conclusion NCC is expressed in neonatal cardiac myocytes and the expression level was decreased after birth. Pathological condition, such as ischemic heart disease and heart failure, upregulated NCC expression in cardiomyocytes and NCC exacerbated lethal myocyte injury, while roles of NCC in physiological beating are little. Funding Acknowledgement Type of funding sources: None.