Altered ambulatory activity and related brain monoamine metabolism in genetically obese Zucker rats

Feeding-related behavior and alteration of brain monoamine metabolism were examined in the male lean, and obese Zucker rats. Ambulatory activity of obese rats was reduced in the dark cycle. Dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), contents were significantly decreased in the striatum of obese rats. However, the metabolic rate assessed with the DOPAC/DA ratio, and norepinephrine (EN) content were not changed in the striatum. Hypothalamic DA and NE contents were significantly reduced and the DOPAC/DA ratio was significantly increased in the hypothalamus of obese rats. The present findings suggest that the observed changes in brain monoamine metabolism may contribute to the development of obesity reducing ambulatory activity of obese rats.