Lack of cross-tolerance between disodium cromoglycate and veratrum alkaloids

We sought to determine if the hypotension and bradycardia caused by disodium cromoglycate (DSC) and veratrine sulfate were due to an action upon a common receptor. Tolerance rapidly developed to the hypotensive and bradycardic action of 10 μg/kg iv DSC in anesthetized dogs. Veratrine sulfate 30 μg/kg iv given after tolerance had developed to DSC gave falls in blood pressure and heart rate identical to those produced by the alkaloid before DSC tolerance had set in. Thus, no cross-tolerance between DSC and veratrine was observed. This result excludes the possibility of a common site of action for DSC and veratrine.