Cyclic somatostatin (SRIF-14) is a growth hormone-release inhibiting factor used in the research of severe, acute hemorrhages of gastroduodenal ulcers. Cyclic somatostatin is a neuropeptide co-stored with acetylcholine in the cardiac parasympathetic innervation, exerts influences directly on contraction of ventricular cardiomyocytes. Cyclic somatostatin inhibits the contractile response of isoprenaline with an IC50 value of 13 nM. Cyclic somatostatin can be used for the research of cardiovascular disease.