tokens: Experiments on narcotized cats demonstrated that the derivatives of 2 - mercaptobenzimidazole possessing the properties of specific bradycardic agents and coded as CM - 251 , CM - 266 , and CM - 345 , reduce the mean rise of segment ST on numerous leads of the epicardial electrogram during 5 - min occlusion of the anterior descending branch of the left coronary artery .