L-type (CaV1), voltage-gated Ca2+ channels are plasma membrane protein complexes which allow the passage of Ca2+ ions into cells following depolarization of the membrane potential.
L-type channels are widely expressed in cardiac and smooth muscle in which they control contraction and therefore were recognized as a therapeutic target for cardiovascular diseases.
Dihydropyridines (DHP) are molecules that acts as allosteric modulators of L-type channels and many are used in the clinic to treat hypertension. Amlodipine besylate is a DHP that acts as a L-type, voltage-gated Ca2+ channel blocker and is used in the clinic to treat hypertension. Amlodipine inhibit Ca2+ -induced contractions in depolarised rat aorta (IC50 1.9 nM) but, displayes a very slow onset of action. Contractions induced by depolarising steps with 45 mM K+ are much less potently blocked by amlodipine (IC50 19.4 nM) and guinea pig papillary muscle single-cell slow action potentials are blocked at a concentration of 5 mM4. Amlodipine besylate inhibits L- and T-type CaV channels with similar potency.