ZM 241385, an adenosine A(2A) receptor antagonist, inhibits hippocampal A(1) receptor responses

4-(2-[7-amino-2-(2-furyl?1,2,4?-triazolo?2,3a?-?1,3, 5?triazin-5-yl-amino]ethyl)phenol (ZM 241385) has been used as an antagonist of adenosine A(2A) receptors, exhibiting high selectivity over adenosine A(1) receptors. We now report that ZM 241385 (10-50 nM) attenuated the inhibitory action of N(6)-cyclopentyladenosine (10 nM) and R(-)-N(6)-phenylisopropyladenosine (R-PIA, 20 nM), two selective adenosine A(1) receptor agonists, on hippocampal population spike amplitude. This effect is unlikely to be a direct antagonism of adenosine A(1) receptor since the K(i) of ZM 241385 to displace [3H]PIA (2 nM) binding, from hippocampal membranes ranged from 0.8 to 1.9 microM. These results question the usefulness of ZM 241385 to define adenosine A(2A) receptors actions in functional studies.