Mode of action of OB protein (leptin) on feeding

OB protein (leptin) decreases food intake in a variety of species. Here we investigated the effects of the intracerebroventricular administration of recombinant murine OB protein on food consumption and meal parameters in Wistar rats maintained ad libitum. The intracerebroventricular administration of OB protein (0.56-3.5 mu g/rat) decreased feeding in a dose-dependent manner. Computer analysis of meal parameters demonstrated that OB protein (3.5 mu g/rat, n = 10) decreased nighttime meal size by 42%, whereas meal frequency and meal duration were unaffected. Derived analyses for the nighttime also showed that OB protein decreased the feeding rate (meal size/meal duration) by 30%, whereas the satiety ratio (intermeal intervals/meal size) increased by 100%. A similar profile was observed during the daytime and total daily periods. The intracerebroventricular administration of heat-inactivated OB protein (3.5 mu g/rat, n = 10) had no effect on any meal parameter. The results show that OB protein administered intracerebroventricularly inhibits feeding through a specific reduction of meal size.