Ontogeny of brain monoamines in lean and obese female Zucker rats

Differences in monoamine and metabolite levels were previously observed between lean and obese 16 week-old female Zucker rats. In order to test whether these variations exist initially in young animals, catecholamines (CA), serotonin (5-HT) and some of their metabolites were assayed in brain areas of Zucker rats between 5 and 16 weeks of age. The levels of most compounds in all areas studied increased with age in both groups. At 5 weeks of age, there was no difference between lean and obese rats. At 8 weeks, a reduction of dopamine (DA) metabolites appeared in the striatum and cortex of obese rats and persisted up to 16 weeks. A reduction of the 5-HT metabolite, 5-hydroxyindolacetic acid (5-HIAA), occurred at 8 weeks only. At 16 weeks, increases of DA and 5-HT in the hypothalamus and decreases of norepinephrine (NE), 5-HT and 5-HIAA in the hippocampus appeared. These data suggest that the development of obesity occurs before any monoamine alterations.