Mescaline-induced scratching (MiS) in mice can be blocked by several antipsychotics, such as haloperidol, risperidone and clozapine. Here we investigate the contribution of dopaminergic, serotonergic and glutamatergic neurotransmission to this behavior. Mescaline-induced scratching is not attenuated by the dopamine D2-like receptor antagonists, sulpiride (30 mg/kg ip) and amisulpride (20 mg/kg ip), or by the selective D3 antagonist, A-437203, suggesting that MiS does not depend on dopamine D2 or D3 receptor stimulation. The 5-HT2 antagonist ketanserin, however, blocks MiS at doses of >0.1 mg/kg. Given that haloperidol, risperidone and clozapine block both, D2 and 5-HT2A receptors, it is likely that these effects are due to antagonism of 5-HT2A, but not D2-like receptors. MiS can be blocked by glutamate mGluR2/3 receptor agonists and potentiators, indicating a role of glutamatergic neurotransmission in this model (Gross at al., SfN 2004, Progr. No. 1030.16). Here we show that blockade of AMPA receptors with...