Increased sucrose intake and corresponding c-Fos in amygdala and parabrachial nucleus of dietary obese rats

The intake-excitatory effects of caloric foods are mainly due to the palatable taste and the ensuing positive postingestive effects. Dietary obese individuals are inclined to overeat high caloric foods. However, it is still unclear whether the taste or postingestive reinforcement mainly contributes to the excessive intake by obese individuals. In the present study, we measured 10- or 120-min sucrose solution drunk by dietary obese rats and measured c-Fos expression following 120-min tests in the central nucleus of amygdala (CeA), a forebrain nucleus involved in the hedonic reward and craving, and the parabrachial nucleus (PBN), a taste relay area responsive to positive postingestive effects. Dietary obese rats, compared with those fed normal chow, ingested larger amounts of sucrose solution (0.25 M) in the 120-min test, but not in the 10-min test. In addition, significantly more sucrose-induced c-Fos positive cells were found in the CeA, but much less in the external lateral subnucleus of the PBN of dietary obese rats. Our results demonstrate that increased sucrose intake in dietary obese rats is mainly due to the alteration of postingestive effects. The differences in these postingestive effects in obesity may involve greater positive/excitatory signals in which the CeA may play a role, and less negative/inhibitory signals in which the el-PBN may be involved.

► No difference in 10-min sucrose intake was found between obese and normal rats.
► Obese rats drank more sucrose solution in 120 min than normal rats did.
► FLI in the CeA and el-PBN induced by sucrose intake were more than those by water.
► Sucrose-induced FLI in the CeA in obese rats was more than that in normal rats.
► Sucrose-induced FLI in the el-PBN in obesity was less than that in normal rats.