Psilocin is a high-affinity agonist at serotonin 5-HT2A receptors, which are especially prominent in the
prefrontal cortex. It increases cortical activity secondary to down-stream postsynaptic
glutamate effects. It is also active at 5-HT1A, 5-HT1D, and 5-HT2C receptors, although these are thought to play a lesser role in its effects. In the presence of the 5-HT2A antagonist
ketanserin, the changes in mental state that psilocybin typically causes do not occur.258 Although psilocybin has no affinity for dopamine D2 receptors, a PET study using the D2 receptor ligand
raclopride showed that psilocybin increases
dopamine transmission in the striatum, probably through secondary increases in dopamine.259,260 Some psilocybin-containing mushrooms contain
phenylethylamine, which may contribute to
sympathomimetic effects.