| Abstract
| - Several 4-substituted 1-acylpiperazines, obtained by molecular simplification of 4-substituted1,4-diazabicyclo[4.3.0]nonan-9-ones, have been synthesized and tested in vivo on the mousepassive avoidance test, to evaluate their nootropic activity. The results show that, apparently,an N-acylpiperazine group can mimic the 2-pyrrolidinone ring of 1,4-diazabicyclo[4.3.0]nonan-9-one, as the compounds of the new series maintain high nootropic activity. Moreover molecularsimplification produces more clear-cut structure−activity relationships with respect to theparent series. The mechanism of action also appears to be similar in the two series. In fact,although the molecular mechanism remains to be elucidated, the most potent compound ofeach class (DM232 and 13, DM235) is able to increase acetylcholine release in rat brain.Piperazine derivatives represent a new class of nootropic drugs with an in vivo pharmacologicalprofile very similar to that of piracetam, showing much higher potency with respect to thereference compound. Among the compounds studied, 13 (DM235) shows outstanding potency,being active at a dose of 0.001 mg kg-1 sc.
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