Dihydropyridine Ca2+ agonists and channel blockers interact in the opposite manner with photogenerated unpaired electrons.

Interaction of Ca2+-channel antagonists (felodipine, ryocidil, verapamil, diltiazem) and agonists (dihydropyridine derivatives Bay K 8644 and CGP 28392) was studied by the methods of absorption spectroscopy. Ca2+-channel antagonists were found to act as electron donors, the agonists being electron acceptors in the interaction with dye free radicals in solution. Redox transitions in channel-forming protein were proposed as a possible mechanism of the modulation of channel activity by the compounds tested.