Effects of Ca2+ antagonists on 45Ca2+ uptake by rat whole brain P1 and P2 fractions.
Voltage-dependent 45Ca2+ uptake into rat whole brain P1 (nonsynaptosomal) and P2 (synaptosomal) fractions was measured after 60-s KCl-stimulated depolarization to investigate possible inhibitory effects of Ca2+ antagonists, nitrendipine, diltiazem, verapamil and ifenprodil tartrate. All drugs (10(-5)M) had little influence on 45Ca2+ uptake by whole brain P1 fraction in both nondepolarizing and depolarizing mediums. Diltiazem (10(-5)M) had no influence on 45Ca2+ uptake by whole brain P2 fraction under both conditions. However, nitrendipine (10(-5)M) verapamil (10(-5)M) and ifenprodil tartrate inhibited depolarization-dependent 45Ca2+ uptake by whole brain P2 fraction, while nondepolarization-dependent 45Ca2+ uptake was not affected by these drugs. The inhibitory sequence of depolarization-dependent 45Ca2+ uptake by P2 fraction was: ifenprodil tartrate greater than nitrendipine greater than verapamil. These results suggest that ifenprodil tartrate, nitrendipine and verapamil specifically inhibit depolarization-dependent synaptosomal 45Ca2+ uptake, but that diltiazem has little influence on it.
Department of Biomedical Sciences, University of Illinois, College of Medicine, Rockford 61107-1891.
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Honda
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Shibuya
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Salafsky
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002132:Calcium Radioisotopes; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D002132:Calcium Radioisotopes; D009467:Neuromuscular Depolarizing Agents; D011188:Potassium; D002118:Calcium