Brain pharmacokinetics and in vivo receptor binding of 1,4-dihydropyridine calcium channel antagonists.
Brain pharmacokinetics of 1,4-dihydropyridine (DHP) calcium channel antagonists and their in vivo receptor binding in mice were characterized. The area under the concentration vs time curve (AUCbrain) for [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 in mouse brain after intravenous injection was higher than that for [3H]amlodipine. Brain/plasma concentration ratios (AUCbrain/AUCplasm) for [3H]nimodipine and [3H]PN 200-110 were 3 to 5 times higher than those for [ H]nifedipine and [3H]amlodipine. Further, brain/heart concentration ratios (AUCbrain/AUCheart) for [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 were about 20 times higher than the ratio for [3H]amlodipine. A significant amount of specific binding in particulate fractions of mouse brain was detected in vivo by intravenous injection of [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 but not [3H]amlodipine. These data suggest that [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 are more extensively taken up into brain from plasma than [3H]amlodipine and bind to the receptor sites in brain parenchymal cells in a significant amount in vivo. In conclusion, the present simultaneous measurement of pharmacokinetics and in vivo receptor binding in mouse brain suggests an usefulness of calcium channel antagonists such as nimodipine in the pharmacotherapy of brain diseases.