The atypical antipsychotic olanzapine enhances ingestive behaviour in the rat: a preliminary study

The weight gain associated with several antipsychotic drugs, most notably the newer 'atypical' compounds olanzapine and clozapine, introduces problems of compliance and morbidity in the treatment of schizophrenia. The mechanisms underlying this process have been little studied due to the lack of models of the effects of antipsychotic drugs on weight gain and/or feeding behaviour in vivo. Here, we report how the effects of olanzapine (0.5 mg/kg, i.p.) on ingestive behaviour were investigated in the food-deprived rat using a runway to food goal paradigm. Compared with vehicle-treated animals, olanzapine delayed the reductions in food intake and in running speed that occurred after the first trial blocks, without effects on starting speed. These results indicate that olanzapine can increase feeding behaviour through a suppression of satiety, suggesting a mechanism for its effects on weight gain and also providing an acute model for further assessment of the underlying pharmacology.