<Li> Ethanol (alcohol)--a euphoriant, sedative, and anxiolytic used recreationally; unknown site antagonist </Li> <Li> Guaifenesin--an expectorant </Li> <Li> Huperzine A--a naturally occurring acetylcholinesterase inhibitor and potential antidementia agent </Li> <Li> Ibogaine--a naturally occurring hallucinogen and antiaddictive agent </Li>

What evidence does not support the role of nmda receptors in learning and memory