Cardiotropic effects of somatostatin and its antagonists

Somatostatin reduces cardiac rhythm in cats, the effect being abolished by the M-cholinolytic methacin, the ganglioblocker benzohexonium, or somatostatin antagonist. Somatostatin suppressed vagal chronotropic effect by reducing its tonic component, while the synchronizing vagal component increases. The antagonist of somatostatin exerts an opposite effect: it eliminates the influence of somatostatin on the tonic vagal component and reverses its effect on the synchronizing component.