ADENOSINE A(2A) RECEPTORS STIMULATE ACETYLCHOLINE-RELEASE FROM NERVE-TERMINALS OF THE RAT HIPPOCAMPUS

The nature of the adenosine receptors involved in the enhancement of a cetylcholine release in the hippocampus was studied. The A(2A) agonist , CGS 21680, increased the veratridine-evoked release of [H-3]acetylch oline from hippocampal synaptosomes, This presynaptic effect of CGS 21 680 was greater at 3-30 nM than at 100 nM. The excitatory effect of CG S 21680 was antagonised by the A(2) antagonist, DMPX (10 mu M), and by the A(2A) antagonist, CSC (200 nM), but not by the A(1) antagonist, D PCPX (20 nM). We also found co-expression of A(2A) and choline acetylt ransferase mRNAs in the nucleus of the diagonal band and the medial se ptum, where the cholinergic cell bodies that project into the hippocam pus are located. These results indicate that A(2A) adenosine receptors are present in cholinergic nerve terminals in the hippocampus and tha t activation of these receptors enhances acetylcholine release.