Failure of Coronary blood vessels to adequately supply cardiac myocytes with oxygen underlies ischaemic heart disease and ultimately myocardial infarction. Thus it is important to determine the factors that regulate coronary blood flow in order to understand the pathophysiology of such conditions and, conceivably, identify new therapeutic targets for their treatment. Calcium-activated chloride channels, encoded by TMEM16A, play a key role in depolarising vascular smooth muscle cell (VSMC) membrane potentials, thus causing influx of Ca2+ through voltage gated Ca2+ channels and ultimately VSMC contraction. The aim of this study was to determine whether TMEM16A was expressed in rat coronary arteries and whether it’s modulation by novel TMEM16A specific blockers affected coronary artery function. Male wistar rats were killed in accordance with Schedule 1 of the United Kingdom Animals Act (1986) or Danish regulations. 1st and 2nd order left anterior descending (LAD) coronary artery segments or septal coronary artery segments were isolated. A geNorm experiment was carried out to find out the shared most stably expressed genes across all vessels compared to which the abundance of the genes of interest would be normalised. TMEM16A mRNA was detected in coronary arteries although at levels lower than rat pulmonary arteries. To study the role of TMEM16A in vascular physiology isometric tension recordings were carried out on LAD and septal segments. Cumulative application of U46619 (1nM – 3uM) produced concentration dependent contractions that were attenuated with prior application of TMEM16A specific blockers (T16inh-A01 and MONNA). 10uM T16inh-A01 caused a shift in EC50 of U46619 from 66nM±9 in vehicle controls to 285nM±59 (n=10, p<0.001) while 10uM MONNA caused a shift from 66nM±9 to 317nM±107 (n=8, p<0.005). Shifts in EC50 were also seen with 3uM T16inh-A01 (n=7, p<0.001) and 1uM MONNA (n=8, p<0.01), while 1uM T16inh-A01 and 0.3uM MONNA both had no effect on the contraction (both n=7). Values are mean EC50s ± S.E.M, compared by 1-way-ANOVA to vehicle controls. In Langendorff perfused rat heart preparations increasing concentrations of T16inh-A01 (10nM -10uM) produced a concentration dependent increase in coronary flow of ~60% (n=4). We have shown the presence of TMEM16A in rat LAD and Septal coronary arteries and demonstrated that TMEM16A-specific blockers attenuated U46619 induced contractions and increased coronary flow.