L-type Ca2+ channels are important targets for drugs, such as dihydropyridines (DHPs), in the treatment of cardiovascular diseases. Channel expression is regulated by alternative splicing. It has been suggested that in the cardiovascular system tissue-specific expression of different L-type Ca2+ channel splice variants may underlie the observed differences in sensitivities to channel block by DHPs. We investigated the sensitivity of Ca2+ channel splice variants derived from the human alpha1C gene to the DHP isradipine. Among seven alpha1C channels we observed up to 10-fold differences in IC50 values for isradipine, as well as changes in the voltage dependence of DHP action.