Effect of adenosine A(2A) receptor stimulation on GABA release from the striatum of young and aged rats in vivo

THE effect of the adenosine A(2A) receptor agonist CGS 21680 on GABA releas e from the striatum was investigated in vivo in young and old rats by micro dialysis experiments. CGS 21680 at 10 mu M significantly increased GABA spo ntaneous outflow in young but not in old rats. Conversely, CGS 21680 signif icantly increased potassium-evoked GABA release in old but not in young rat s. The stimulating effect of CGS 21680 on spontaneous GABA release may be b oth secondary to an increased outflow of excitatory amino acids and to the removal, brought about by A(2A) receptor stimulation, of the inhibitory inf luence exerted by dopamine through D-2 receptors on GABA-enkephalinergic ne urones. The stimulating effect of CGS 21680 on potassium-evoked GABA releas e in old rats may be ascribed to an age-dependent imbalance in favour of ad enosine us dopamine, recently described in the striatum of old rats. (C) 19 99 Lippincott Williams & Wilkins.