Glucose tolerance and serum insulin levels in an animal model of obesity induced by the antipsychotic drug, sulpiride.

To assess the role of insulin in the development of obesity induced by antipsychotic drugs, a glucose tolerance test was conducted in 40 female rats during the peak of sulpiride-induced weight gain and in 40 vehicle-treated animals. The glucose area under the curve did not differ between the groups (P = 0.24), however, the area under the insulin curve was significantly decreased by sulpiride (55.2 +/- 2.8 versus 115.6 +/- 18.9, P = 0.007). The results suggest that insulin resistance and hyperinsulinaemia are not involved in the excessive weight gain observed in this animal model of drug-induced obesity. Alternatively, the insulin-dampened response observed in the sulpiride-treated rats may be related to increased insulin sensitivity, which may promote weight gain as proposed by Ravussin (1995).