A(1), BUT NOT A(2A), ADENOSINE RECEPTORS MODULATE ELECTRICALLY STIMULATED [C-14] ACETYLCHOLINE-RELEASE FROM RAT CORTEX

Adenosine A(1) receptors are known to be widely distributed in various regions of the brain. A(2A) receptors are enriched in the dopamine-ri ch areas of the brain, but are also present in rat cortex. Electricall y stimulated, perfused rat cortical slices were used to examine the in fluence of interactions between A(1) and A(2A) receptors on the releas e of acetylcholine (ACh) from cortical cholinergic nerves. The A(1)-se lective agonist, N-6-cyclopentyladenosine (CPA) caused a dose-dependen t inhibition of ACh release, which was attenuated in the added presenc e of the A(1)-selective antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 1 mu M). The inhibitory effects of CPA were unaltered in the a dded presence of the A(2)-selective antagonist 4-dimethyloxystyryl)-1, 3-dipropyl-7-methylxanthine (KF 17837; 1 mu M). The A(2A)-selective ag onist yl)-phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680), over the concentration range 1 nM to 10 mu M, did not significantly al ter ACh release when given alone or in the presence of DPCPX or KF 178 37. These data suggest that the A(2A) receptors previously identified in rat cortex are not functionally coupled to modulation of ACh releas e in this tissue. This does not exclude that these receptors may regul ate the release of other neurotransmitters.