Alstonine is a pentacyclic alkaloid and putative antipsychotic constituent of various plant species including Alstonia boonei, Catharanthus roseus, Picralima nitida, Rauvolfia afra and Rauvolfia vomitoria. In preclinical studies alstonine attenuates MK-801-induced hyperlocomotion, working memory deficit and social withdrawal. It also possesses anxiolytic-like effects in preclinical studies, attenuates amphetamine-induced lethality and stereotypy as well as apomorphine-induced stereotypy, and attenuates haloperidol-induced catalepsy. These effects appear to be mediated by stimulation of the 5-HT<sub>2C</sub> receptor. In addition, alstonine, similarly to clozapine, indirectly inhibits the reuptake of glutamate in hippocampal slices. Unlike clozapine however, the effect of which is abolished by the D<sub>2</sub> receptor agonist apomorphine, alstonine requires 5-HT<sub>2A</sub> and 5-HT<sub>2C</sub> receptors to produce this effect, as it is abolished by antagonists of these receptors. Also unlike clozapine, alstonine lacks pro-convulsant activity in mice.