REGULATION OF EXTRACELLULAR ADENOSINE LEVELS IN THE STRIATUM OF AGINGRATS

Extracellular adenosine concentrations, evaluated by microdialysis in the striatum of young and aged rats, were 66.8 +/- 0.7 and 71.6 +/- 1. 0 nM, respectively. The adenosine deaminase inhibitor EHNA (100 mu M) increased the extracellular adenosine levels in young rats only. The a denosine kinase inhibitor iodotubercidin (10 mu M) brought about the s ame increase in young and aged rats. In aged rats the resting adenosin e outflow was reduced by the N-methyl-D-aspartate (NMDA) receptor anta gonist D-(-)-2-amino-7-phophonoheptanoic acid (D-AP7) (1 mM). It is co ncluded that extracellular levels of adenosine in the striatum are not affected by age, irrespective of the differences in adenosine deamina se activity and that the release of excitatory amino acids is responsi ble for much of resting adenosine outflow in aged but not in young rat s.