Effects of adenosine receptor agonists and antagonists on acquisition of passive avoidance learning

Abstract

A series of experiments examined the effect of the adenosine receptor agonists N 6- cyclohexyladenosine (CHA), N 6- p phenylisopropyladenosine ( R- PIA ) and 5′-N- ethylcarboxamidoadenosine (NECA); the adenosine receptor antagonists theophylline, caffeine and 8-phenyltheophylline (8-PT), and the adenosine uptake inhibitor dipyridamole on acquisition of a single trial passive avoidance learning by mice. The adenosine receptor agonists CHA (0.05, 0.1, 0.2 and 0.4 mg/kg) and R- PIA (0.0625, 0.125, 0.25 and 0.5 mg/kg) administered 1 h before the training session decreased retention dose dependently while the other adenosine receptor agonist NECA (0.0025, 0.005 and 0.01 mg/kg) had no effect. The response induced by the adenosine receptor agonists CHA and R- PIA was attenuated by the pretreatment of animals with low doses of the adenosine receptor antagonists 8-PT (2.0 mg/kg) and theophylline (25 mg/kg) but not with higher doses of the antagonists. The higher doses of the antagonists decreased the passive avoidance. Dipyridamole (7.5, 15, 30, 60 and 120 mg/kg) showed no significant effect. It is concluded that adenosine A 1 receptor activation decreases the acquisition of a passive avoidance response.