Habituation of exploratory activity in rats: Action of N⁶phenylisopropyladenosine, caffeine and their combination

1. 1. L-PIA (0.2 mg/kg), caffeine (15 mg/kg) and their combination were given subcutaneously to rats tested in open field. 2. 2. The acute administration of L-PIA reduced ambulation. Caffeine alone was ineffective but increased ambulation in combination with L-PIA. These effects may have been determined by an interaction of L-PIA and caffeine on adenosine receptors. 3. 3. Tolerance to L-PIA was observed after a chronic administration (20 days). The chronic administration of caffeine alone or in combination with L-PIA increased ambulation. 4. 4. In the habituation test the reduction of ambulation in the 3 successive trials was increased by L-PIA. Caffeine did not antagonize the L-PIA effect and, in part, had the same effect. These results suggest that L-PIA and, in part, caffeine improve memory consolidation in open field and do not support the notion that L-PIA and caffeine action on memory processes is due to an interference on adenosine receptors.