Racetams are a class of drugs that share a pyrrolidone nucleus. Some, such as piracetam, are considered nootropics. Some such as aniracetam, oxiracetam and phenylpiracetam are also nootropics. Others such as levetiracetam and seletracetam are anticonvulsants.
There is no universally accepted mechanism of action for racetams. Racetams generally show negligible affinity for common central nervous system receptors, but modulation of central neurotransmitters, including acetylcholine and glutamate, has been reported. Although aniracetam and nebracetam show affinity for muscarinic receptors, only nefiracetam demonstrates nanomolar interactions. Modification of membrane-located mechanisms of central signal transduction is another hypothesis.
Racetams are understood to work by activating glutamate receptors that are colocalized with cholinergic receptors, thus increasing the frequency of activation of the latter. Racetams are posited to enhance memory through interaction with cholinergic and glutamate receptors in the central nervous system.
In studies with aged rats, marked improvement has been observed in cognitive tasks in experimental groups given piracetam. Performance was further increased with piracetam combined with cholines. Evidence in studies with rats has indicated that the potency of piracetam is increased when administered with choline.
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The R-configuration enantiomers of methylphenylpiracetam are more active positive allosteric modulators of Sigma-1 receptor than S-configuration enantiomers.
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