here , we describe the effects of nitrendipine ( ntr ) ( a dihydropyridine 'antagonist ' of l-type calcium channels ) , bay k 8644 ( bk ) ( a dihydropyridine calcium channel 'agonist ' ) , cobalt and manganese ions ( both inorganic calcium channel blockers ) , and low external calcium concentrations , on the melatonin rhythm .
C0028127
nitrendipine
C0012315
dihydropyridine