Nimodipine inhibits [ 3H]nitrobenzylthioinosine binding to the adenosine transporter in human brain

The inhibition of [ 3H]nitrobenzylthioinosine ([ 3H]NBI) binding to human parietal cortex membranes by adenosine transport inhibitors, adenosine receptor agonists and antagonists and dihydropyridines was investigated. While the adenosine transport inhibitors inhibited [ 3H]NBI binding with K i values in the low nanomolar range and the adenosine A 1 receptor agonist, cyclopentyladenosine, with a K i in the low micromolar range, no IC 50 values could be obtained for the adenosine receptor antagonists at concentrations up to 100,000 nM. Among the dihydropyridines (+)-nimodipine was the most potent with a K i of 201±55 nM. Inhibition of adenosine transport thus may contribute to the clinical effects of nimodipine in the central nervous system.