Inhibition of adenosine responses of rat hippocampal neurones by nifedipine and BAYK 8644.

The application of adenosine to hippocampal slices caused a suppression of evoked population spikes in the CA1 region. This effect was enhanced by nifedipine and BAYK 8644 in control slices but was reduced by these dihydropyridines in the presence of dipyridamole. Several analogues of adenosine which are not substrates for the uptake system also depressed the population spikes in the CA1 region but these responses were inhibited by nifedipine and BAYK 8644. Other dihydropyridines including nimodipine and nitrendipine did not affect sensitivity to adenosine or its analogues. It is concluded that some agonist and antagonist dihydropyridines can inhibit adenosine uptake and thus potentiate its effects but can also antagonise receptor activation. Structural features of nifedipine and BAYK 8644 may be specific for a population of dihydropyridine receptors closely linked functionally with the adenosine receptor.