Obesity induced by unspecific early postnatal overfeeding in male and female rats: hypophagic effect of CCK-8S.

The response to cholecystokinin (CCK) as a satiety peptide in obesity or anorexia has been tested mainly in extreme models of food intake control. In the present study, the effect of CCK-8S on food intake was investigated in a nongenetic and less-stressful model of obesity due to unspecific early postnatal overfeeding in male and female rats. Reducing the normal litter size of ten to three newborn rats on day 3 of life led to an enhanced food intake resulting in an increased body weight until adulthood. Freely fed male and female, normal and obese rats were given 10 micrograms/kg CCK-8S i.p. on day 41 and 40 micrograms/kg CCK-8S on day 91 of life and food intake was measured for 24 h. Compared with treatment with saline (i.p.) 1 day before the test, the lower dose of 10 micrograms/kg CCK-8S reduced food intake for 2 h in normal, but not in obese rats. Conversely, the higher dose of 40 micrograms/kg CCK-8S reduced food intake in both normal and obese rats for 2 h, but this effect was more evident in the obese rats. Moreover, the satiating effect of CCK-8S was more pronounced and longer lasting in male than in female rats. In summary, the data suggest that the response to CCK-8S differs in normal and obese rats and depends on sex.