2-Chloroadenosine, a preferential agonist of adenosine A1 receptors, enhances the anticonvulsant activity of carbamazepine and clonazepam in mice

2-Chloroadenosine (0,25-1 mg/kg) significantly raised the threshold for electroconvulsions in mice. This preferential adenosine A(1) receptor agonist (at 0.125 mg/kg) significantly potentiated the protective activity of carbamazepine against maximal electroshock-induced seizures in mice. 2-Chloroadenosine 0 mg/kg) showed also anticonvulsive efficacy against pentylenetetrazol-evoked seizures, raising the CD value for pentylenetetrazol from 77.2 to 93.7 mg/kg. The drug (at 0.5 mg/kg) significantly enhanced the protective action of clonazepam in this test, decreasing its ED50 value from 0.033 to 0.011 mg/kg. Moreover, aminophylline, a non-selective adenosine receptor antagonist (5 mg/kg). and 8-cyclopentyl-1,3-dimethylxanthine (8-CPX), a selective A, adenosine receptor antagonist (5 mg/kg) reversed the 2-chloroadenosine (0,125 mg/kg)-induced enhancement of the protective activity of carbamazepine and clonazepam. 2-Chloroadenosine administered alone or combined with antiepileptic drugs, caused neither motor nor long-term memory impairment. Finally, the adenosine A, agonist did not change the free plasma concentration of antiepileptics. so a pharmacokinetic factor is not probable. Summing up, 2-chloroadenosine potentiated the protective activity of both carbamazepine and clonazepam, which seems to be associated with the enhancement of purinergic transmission mediated through adenosine A, receptors. (C) 2002 Published by Elsevier Science BV/ECNP.