Phenylalkylamines, calcium channel blocking

L-type or high-voltage-activated calcium channels carry the majority of the calcium inward current in smooth muscle cells. They start to activate at a high membrane potential (around -30 mV) with a maximum at slightly positive membrane potentials (around -f-10 mV), have a large conductance (20-25 pS with 110 mM Ba2+ as charge carrier), inactivate slowly, and are readily and specifically blocked by the classic organic calcium channel blockers nifedipine (a 1,4-dihydro-pyridine), verapamil (a phenylalkylamine), and dil-tiazem (a benzothiazepine) (see Hofmann etah, 1994). 

Motoike HK, Bodi I, Nakayama H, Schwartz A, Varadi G. A region in IVS5 of the human cardiac L-type calcium channel is required for the use-dependent block by phenylalkylamines and benzothiaz-epines. 7 Sio/ Chem 1999 274(14) 9409-20. 

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