CGS 15943 A (a nonxanthine
adenosine antagonist) was studied on the protective efficacy of
carbamazepine (60 min prior to the convulsive test),
diazepam (60 min),
diphenylhydantoin (120 min),
phenobarbital (120 min), and
valproate (30 min) against maximal electroshock-induced convulsions in mice. Moreover, the influence of the
adenosine antagonist on
2-chloroadenosine (1 mg/kg, 20 min prior to the test)- and
valproate (250 mg/kg, 30 min)-induced inhibitions of locomotor activity was also studied.
CGS 15943 A (1 mg/kg) was given 15 min before both tests and all the drugs were administered i.p.. The
adenosine antagonist (1 mg/kg) remained without influence upon the protective activity of all studied
antiepileptics, reflected by their respective ED50 values against maximal electroshock. However, both
2-chloroadenosine and
valproate-induced inhibitions of locomotor activity were attenuated by
CGS 15943 A, which alone did not affect this parameter. However,
CGS 15943 A (5 mg/kg) diminished the protection offered by
diphenylhydantoin, increasing its ED50 value from 13 to 16 mg/kg. It may be concluded that the protection provided by common
antiepileptic drugs against electroconvulsions seems independent of
adenosine-mediated inhibition. In the case of
diphenylhydantoin, one may suggest the involvement of purinergic transmission in the final
anticonvulsant effect.