Striatal A2A adenosine receptor antagonism differentially modifies striatal glutamate outflow in vivo in young and aged rats.

The effect of the adenosine A2A receptor antagonist SCH 58261 on glutamate release was investigated in the striatum of young and old rats by microdialysis experiments. SCH 58261 (50 nM) signi®cantly decreased the spontaneous and K - evoked glutamate out¯ow in young rats. In aged rats, spontaneous glutamate out¯ow was signi®cantly reduced in comparison to young rats and SCH 58261 signi®cantly increased spontaneous and K -evoked glutamate out¯ow. It is suggested that the opposite effects of the A2A antagonist on glutamate out¯ow in young and aged rats can be respectively attributed to blockade of striatal A2A adenosine receptors located on glutamatergic terminals and on the striatal indirect output pathway.