A sex difference in the effect of CCK-8 on food and water intake in obese (ob/ob) and lean (+/+) mice

Male and female ob/ob and +/+ mice were tested with CCK-8 (1, 2, 4 and 8 micrograms/kg) administered 15 min prior to 30-min access to solid food after 17.5 hr food deprivation and 15 min prior to 30-min access to water after 17.5 hr water deprivation. The threshold dose for suppressing 30-min food intake was 2 micrograms/kg for all mice. Larger doses of CCK-8 inhibited food intake in male obese and lean mice in a linear fashion. The dose-response relationship for female mice, however, was not linear: lean females failed to suppress food intake following 4 or 8 micrograms/kg and obese females did not suppress food intake at 4 micrograms/kg. There was also a sex difference in the effect on water intake. No dose of CCK-8 changed water intake in lean males and only the 8 micrograms/kg dose decreased water intake in obese males. In contrast CCK-8 (1, 4 and 8 micrograms/kg) increased water intake in obese females, CCK-8 (1 and 8 micrograms/kg) increased water intake in lean females and no dose of CCK-8 decreased water intake in females. These data demonstrate significant sex differences in the effect of CCK-8 on food and water intake in mice.