Meal-stimulated increased concentrations of CCK in the hypothalamus of Zucker obese and lean rats

Abstract

CCK is a putative satiety peptide found to be active when administered peripherally and centrally. Concentrations of CCK have been measured in the brains of fed and fasted animals, but as yet no clear correlation with feeding has been found. In the present experiment rats were sacrificed after a 6-hr fast or 5 min after a meal. Areas of the hypothalamus were removed from these rats and assayed for CCK content. The relationship between obesity and CCK content in specific areas of the brain was also investigated by using Zucker obese and lean rats. In fed rats the CCK concentrations were higher than in fasted rats in the ventromedial hypothalamus (VMH) (56 vs. 42 pg/mg tissue, p<0.005), lateral hypothalamus (38 vs. 27 pg/mg, p<0.01) and supraoptic nucleus (48 vs. 39 pg/mg, p<0.01). In obese rats the concentrations were higher than in lean rats in the VMH (56 vs. 41 pg/mg, p<0.003), dorsal medial hypothalamus (37 vs. 30 pg/mg, p<0.04) and anterior hypothalamus (61 vs. 37 pg/mg, p<0.001). Average concentrations of CCK in all hypothalamic areas were higher in females than males (50 vs. 40 pg/mg, p<0.001). Thus, CCK concentrations in specific areas of the hypothalamus increased with feeding, supporting the potential role of CCK in the central nervous system as a satiety peptide. Further, although the concentrations of CCK in obese rats were higher than those in lean rats, the changes in CCK concentration with feeding were the same, showing that obesity is not a consequence of decreased concentrations or concentration changes of CCK in brain.