[3H]N6-(L-Phenylisopropyl) adenosine binding in brains from young and old rats.

The binding of [3H]N6-(L-Phenylisopropyl) adenosine (L-PIA) to membrane preparations of whole brains from normal male Sprague-Dawley rats 12 and 84 weeks of age, respectively, was examined. Two populations of binding sites, probably corresponding to A1 and A2 adenosine receptors, were detected in both young and old rats. No statistically significant differences between young and old rats were detected but both the numbers of binding sites (Bmax) and dissociation constants (KD) for both high and low affinity binding sites were greater in 84 week old rats. These results were compared to earlier studies of adenosine receptors and related to previously reported changes in sleep with aging in rats.