Validation and pharmacological characterisation of MK-801-induced locomotor hyperactivity in BALB/C mice as an assay for detection of novel antipsychotics

Rationale We evaluated locomotor hyperactivity induced in BALB/C mice by an N-methyl- d -aspartate receptor antagonist MK-801 as an assay for the detection of antipsychotic drugs. Objectives We assessed the effects of antipsychotic drugs to validate the assay (study 1), selective dopamine and serotonin ligands for pharmacological characterisation of the model (study 2) and a number of compounds with efficacy in models of schizophrenia to understand the predictive validity of the model (study 3). Methods Adult males ( n = 9/group) were pretreated with a test compound, habituated to locomotor activity cages before receiving MK-801 (0.32 mg/kg) and activity recorded for a further 75 or 120 min. In study 1, we tested haloperidol, clozapine, olanzapine, risperidone, ziprasidone, aripiprazole, sertindole and quetiapine. In study 2, we tested SCH23390 (D 1 antagonist), sulpiride (D 2 /D 3 antagonist), raclopride (D 2 /D 3 antagonist), SB-277011 (D 3 antagonist), L-745,870 (D 4 antagonist), WAY100635 (5-HT 1A antagonist), 8-OH-DPAT (5-HT 1A agonist), ketanserin (5-HT 2A /5-HT 2C antagonist) and SB-242084 (5-HT 2C antagonist). In study 3, we tested xanomeline (M 1 /M 4 receptor agonist), LY379268 (mGluR2/3 receptor agonist), diazepam (GABA A modulator) and thioperamide (H 3 receptor antagonist). Results All antipsychotics suppressed MK-801-induced hyperactivity in a dose-dependent and specific manner. The effects of antipsychotics appear to be mediated via dopamine D 1 , D 2 and 5-HT 2 receptors. Xanomeline, LY379268 and diazepam were active in this assay while thioperamide was not. Conclusions MK-801-induced hyperactivity in BALB/C mice model of positive symptoms has shown predictive validity with novel compounds acing at M 1 /M 4 , mGluR2/3 and GABA A receptors and can be used as a screening assay for detection of novel pharmacotherapies targeting those receptors.