Ca₂₊ channels and 1,4-dihydropyridine receptors

Evidence that nitrendipine [2,6-dimethylcarbo-ethoxy-5-carbomethoxy-4-(3-nitrophenyl)1,4-dihydropyridine] and other 1,4-dihydropyridines interact at specific sites with which to antagonize or to activate Ca₂₊ channel function, is reviewed. Both pharmacologic and biochemical (radioligand binding) approaches indicate the existence of a specific 1,4-dihydropyridine binding site present in excitable tissues. The mechanisms of differentiation between activator and antagonist ligands are discussed, together with evidence concerning the relationship of the binding site to Ca₂₊ channel function. This site is regulated by chronic drug treatment and the significance of this regulation is discussed.