The CNS stimulation study has been performed on the two semisynthetic adducts of caffeine with Schiffs base of pyrazolone and pyrazolone-pyrimidine nucleus. All the reference drugs and test compounds showed positive effect on CNS stimulation. The conclusion has been drawn from the fact that CNS stimulation effect for pentylene tetrazole is higher than caffeine, Molecule-I (pyrazolone ring) is less active than Molecule-II as the Molecule-II (pyrazolo-pyrimidine ring) is fused ring heterocyclic compound and the synergistic action with caffeine with Molecule-I having less activity than the...