Dissimilarity in Fos and Jun immunoreactivity in hypothalamic regions between obese and lean Zucker rats

The obese Zucker rat, whose genotype is transmitted in an autosomal recessive fashion, is an animal model widely used in the field of obesity. The expression of the nuclear transcription factors c-Fos and c-Jun in the paraventricular nucleus (PVN) and arcuate nucleus (ARC) of the hypothalamus of obese Zucker rats was studied using immunohistochemical methods. PVN and ARC in the hypothalamus are known as centers for the control of food intake. It was observed that the numbers of c-Fos-positive and c-Jun-positive neurons in these regions decreased in obese rats compared to lean rats, and that difference was more evident in the ARC than in the PVN which has to do with the regulation of body weight. The reduction in expression in the ARC of obese rats was greater for c-Jun than for c-Fos. These results suggest a possible difference in Fos immunoreactivity in hypothalamic resistance to circulating satiety factors in genetically obese Zucker rats.