Riedy C A, Chavez M, Figlewicz D P, Woods S C
Department of Psychology, University of Washington, Seattle 98195, USA.
Physiol Behav. 1995 Oct;58(4):755-60. doi: 10.1016/0031-9384(95)00108-u.
Insulin acts in the brain to reduce food intake and body weight. Cholecystokinin (CCK) reduces meal size when administered peripherally. The purpose of these experiments was to examine their interaction. In Experiment 1, Long-Evans rats were infused with vehicle or insulin at doses from 0.5 to 2.0 mU/day into the third cerebral ventricles. Doses of 1.0 mU/day and higher caused reduced body weight. A dose of 0.5 mU/day was therefore taken to be subthreshold. In Experiment 2, rats receiving 0.5 mU/day of insulin intracerebroventricularly had greater suppression of 30-min meal size in response to intraperitoneal CCK-8 at doses from 0.25 to 8 mg/kg than did rats receiving intracerebroventricular saline. By itself, the insulin had no effect on body weight or meal size. However, a change of sensitivity to CCK by control rats over the course of the experiment clouded the interpretation. A third experiment was therefore conducted in which rats received an acute intracerebroventricular injection of insulin (0.1 mU) or saline 1 h prior to a 30-min meal, and IP CCK-8 (4 mg/kg) or saline immediately prior to the meal. As in Experiment 2, insulin, itself, had no effect on meal size but enhanced the anorexic effect of CCK. These results are consistent with the hypothesis that central insulin acts by altering sensitivity to satiety agents.
胰岛素作用于大脑，可减少食物摄入量和体重。胆囊收缩素（CCK）经外周给药时可减小进餐量。这些实验的目的是研究它们之间的相互作用。在实验1中，向Long-Evans大鼠的第三脑室注射载体或剂量为0.5至2.0 mU/天的胰岛素。剂量为1.0 mU/天及更高时会导致体重减轻。因此，0.5 mU/天的剂量被认为是阈下剂量。在实验2中，脑室内注射0.5 mU/天胰岛素的大鼠，相比于脑室内注射生理盐水的大鼠，对腹腔注射剂量为0.25至8 mg/kg的CCK-8时，30分钟进餐量的抑制作用更强。单独使用胰岛素对体重或进餐量没有影响。然而，在实验过程中，对照大鼠对CCK敏感性的变化使结果的解读变得复杂。因此进行了第三个实验，在大鼠进餐前1小时脑室内急性注射胰岛素（0.1 mU）或生理盐水，并在进餐前立即腹腔注射CCK-8（4 mg/kg）或生理盐水。与实验2一样，胰岛素本身对进餐量没有影响，但增强了CCK的厌食作用。这些结果与中枢胰岛素通过改变对饱腹感因子的敏感性来发挥作用的假说一致。
