Olanzapine affects locomotor activity and meal size in male rats

Olanzapine is an antipsychotic drug that frequently induces weight gain accompanied by increased fat deposition as a side effect To investigate how olanzapine affects different aspects of energy balance we used male rats to determine effects on meal patterns food preference locomotor activity and body temperature In two short-term experiments olanzapine was administered via osmotic minipumps In the first experiment we offered rats standard lab chow only In the second experiment we offered rats free choice between chow sucrose and saturated fat In a third experiment olanzapine was chronically administered via the drinking water to determine effects on body composition In each experiment olanzapine decreased locomotor activity and altered meal patterns Olanzapine caused an increase in average meal size accompanied by reduced meal frequency without clearly affecting food preference In the chronic experiment body composition was altered favoring adipose tissue over lean muscle mass despite reductions in overall body weight gain The increase in average meal size implies that the primary effect of olanzapine on feeding is an impairment of the normal satiation process Furthermore energy balance is clearly affected by a reduction in locomotor activity Thus the effects of olanzapine on adiposity do not depend solely on the presence of hyperphagra (C) 2010 Elsevier Inc All nghts reserved